Chapter 1
​List processes needed for the spontaneous origin of life.
a.
b.
c.
d.
simple molecules must polymerize/assemble into polymers;
origin of self-replicating molecules / formation of self-replicating molecules;
simple molecules must become isolated from the surroundings/enclosed in membranes;
non-living synthesis of simple organic molecules.
Outline the role of prokaryotes in the development of an oxygen-rich atmosphere on the
Earth.
a.
b.
c.
d.
e.
f.
g.
h.
early atmosphere was oxygen free;
some prokaryotes could carry out chemosynthesis;
cyanobacteria and other varieties developed the ability to photosynthesize;
used water as hydrogen source so released oxygen;
oxygen began to accumulate in the atmosphere;
more photosynthesis than respiration;
atmosphere changed from a reducing atmosphere to an oxidizing atmosphere;
current life forms depend upon an oxygen-rich atmosphere;
Outline the use of human embryonic stem cells hESC to treat Stargardt’s disease:
a. an inherited form of degeneration of retinal layer/photoreceptor cells/blindness
eye genetic disorder
b. hESC/stem cells can provide/differentiate into healthy retinal cells
c. injecting hESC/stem cells into the retina/eye can restore vision in animal/human trials
Outline the cell theory:
a. living things are composed of cells;
b. cells are the basic/smallest unit of life;
c. cells come from pre-existing cells;
Discuss the endosymbiotic theory for the origin of eukaryotes.
a. mitochondria/chloroplasts were once independent prokaryotes;
b. microorganisms/prokaryotes taken into cell by endocytosis;
c. this larger host cell was heterotrophic; free living prokaryote not digested;
d. kept inside cell and perform respiration/photosynthesis;
e. new living arrangement mutually beneficial / depend on each other to exist as single organism;
f. ancestral eukaryote cell and engulfed prokaryote reproduce as a unit; by binary fission
the engulfed prokaryote provides energy by aerobic respiration for the eukaryote;
g. prokaryote gains protection/nutrition;
h. developing into mitochondria/chloroplasts;
i. mitochondria/chloroplasts have double membranes suggests engulfing by endocytosis
j. mitochondria/chloroplasts have circular naked DNA as prokaryotes;
k. mitochondria/chloroplasts have 70S ribosomes as prokaryotes ;
l. mitochondria/chloroplasts grow and divide like prokaryotic cells;
m. similar size and shape or mitochondria/chloroplasts to prokaryotes
n. mitochondria and chloroplasts cannot survive on their own
p. cristae similar to mesosomes / thylakoid have similar structures in prokaryotes;
q. but theory cannot be falsified as it predicts something occurring in the past;
r. theory does not explain the origins of cilia/flagella/linear chromosomes/meiosis;
s. weaker evidence that cilia/flagella evolved from attached bacteria/spirochetes;
Explain the importance of surface area to volume ratio as a limit to cell size.
a.
b.
c.
d.
e.
f.
g.
as volume of a cell increases, the ratio of its surface area to volume decreases;
rate of exchange of materials/gas/energy is a function of its surface area;
food/oxygen enters through the surface of cells;
wastes leave through the surface of cells;
more metabolic activity in a larger cell means more food and oxygen required;
rate of production of heat/waste/resource consumption is a function of its volume;
at low surface area to volume ratios, exchange of materials takes longer/reduced
efficiency of exchange / vice versa;
h. large volume means longer diffusion time;
i. large volume means more wastes produced;
j. excess heat generated will not be lost efficiently with low surface area to volume ratio ;
k. eventually surface area can no longer serve the requirements of the cell;
l. this critical ratio stimulates mitosis;
m. thus the size of the cell is reduced and kept within size limits;
Describe the characteristics of stem cells that make them potentially useful in medicine.
a. stem cells are undifferentiated cells;
b. embryo cells are stem cells;
c. stem cells have/retain the capacity to divide;
d.
e.
f.
g.
h.
i.
j.
k.
can be used to produce cell cultures/large number of identical cells;
can be used to repair/replace damaged/lost cells/tissue;
stem cells are undifferentiated / have not yet differentiated/specialized;
can differentiate/specialize in different ways / are pluripotent/totipotent;
can be used to form a variety of different tissues / form organs;
used in medical research;
used in treatment of named disease;
stem cells are pluripotent
Discuss the advantages and disadvantages of the use of adult stem cells.
Advantages:
a. adult stem cells can divide endlessly / can differentiate
b. adult stem cells can be used to repair/regenerate tissues
c. fewer ethical objections than with embryonic stem cells
d. adults can give informed consent for use of their stem cells
e. adult source is not killed / source would not have grown into new human / no death of
embryos used to provide stem cells
f. no rejection problems / patient’s own cells used
g. less chance of cancer/ malignant tumor development than from embryonic stem cells
h. most tissues in adults contain some stem cells
Disadvantages:
i. difficult to obtain/collect/find in adult body/very few available
j. some adult tissues contain few/no stem cells
k. adult stem cells differentiate into fewer cell types than embryonic cells /OWTTE
Explain how multicellular organisms develop specialized tissues.
a. only some genes are expressed in each cell type/tissue;
b. tissues therefore develop differently/become differentiated;
c. example would be goblet cell
Explain how the properties of phospholipids help to maintain the structure of cell membranes.
a. phospholipid consisting of head and two tails;
b. head is glycerol and phosphate;
c. tails are fatty acid chains;
d. head hydrophilic and tails hydrophobic;
e. hydrophilic molecules/heads attracted to/soluble in water;
f. hydrophobic molecules/tails not attracted to water but attracted to each other;
g. properties of phospholipids leads to formation of double layer in water;
h. stability in double layer because heads on outer edge are attracted to water and tails are
attracted to each other in middle;
i. phospholipid bilayer in fluid/flexible state because of attraction of non-polar tails to each other;
j. fluidity allows membranes to change shape/vesicles to form or fuse with membrane/fluidity
allows cells to divide;
k. non-polar amino acid side chains attracted to hydrophobic tails;
Describe how the structure of the membrane allows the formation of vesicles.
a.
b.
c.
d.
e.
fluidity of membrane allows change of shape/invagination/formation of vesicles;
phospholipids can move / phospholipid bilayer makes membrane fluid/flexible;
weak bonding between phospholipid tails;
bends/kinks in the phospholipid tails prevent close packing;
cholesterol affects membrane fluidity;
State a reason for using an electron microscope to view this virus rather than a light
microscope.
Electron microscope has a greater resolution and viruses are too small to be viewed under a light
microscope.
Outline the functions of Rough Endoplasmic Reticulum and Golgi Apparatus:
Ribosomes on the Rough ER synthesize polypeptides for secretion and use outside of the cell.
The golgi apparatus performs the function of modifying or altering the proteins. These proteins
are secreted out of the golgi in vesicles, which transport them to the protein membrane.
State three structural differences between the cells of an onion and a honey bee.
Plant cells have no lyosomes, animal cells have lyosomes.
Plant cells have starch granules also which are absent in animal cells.
Explain how materials are transported within a cell between structures X and Y.
a. protein material transported by vesicles;
b. from rER to Golgi apparatus/complex/body/membrane;
c. vesicles bud off from rER/fuse with Golgi membrane due to membrane fluidity;
Describe the process of endocytosis.
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
endocytosis occurs when a membrane encloses a target particle;
fluidity of membrane permits movement of membrane;
membrane sinks inwardly/forms pit/invaginates to enclose particle;
membrane seals back on itself / edges fuse;
one membrane layer / two phospholipid layers enclose particle making vesicle;
inner phospholipid layer of original membrane becomes outer phospholipid layer of
vesicle membrane;
outer phospholipid layer of original membrane becomes inner phospholipid layer of
vesicle membrane;
vesicle breaks away from membrane/moves into cytoplasm;
changes in membrane shape require energy; it is an active process
specific example of endocytosis e.g. pinocytosis, phagocytosis;
Outline, with an example, the process of exocytosis.
a.
b.
c.
d.
e.
f.
g.
vesicles carry material to plasma membrane;
vesicle fuses with membrane;
by joining of phospholipid bilayers;
aided by the fluidity of the membrane;
material released/expelled from the cell;
membrane flattens;
name of example e.g. exocytosis of neurotransmitter / exocrine secretion/endocrine
secretion / hormone secretion / release of cortical granules;
h. outline of example: in the presence of calcium, neurotransmitter vesicles release their
contents into the synapse / hormones released from one cell have an effect on another cell
etc.
Explain how hydrophobic and hydrophilic properties contribute to the arrangement of
molecules in a membrane.
Hydrophilic regions are attracted to and are soluble in water whereas hydrophobic regions are
neither attracted nor soluble in water. Phospholipids have a hydrophilic phosphate head and a
hydrophobic hydrocarbon tail. They form a phospholipid bilayer in membranes, with the
hydrophilic heads facing outwards and the hydrophobic tails facing inwards. Cholesterol being
amphipathic but mainly hydrophobic is located in the hydrophobic region of the membrane.
Hydrophobic proteins are present in the phospholipid bilayer whereas hydrophilic proteins are
present on the membrane surface. Integral proteins are embedded in membranes; they have a
hydrophobic middle region and hydrophilic tails.
However, peripheral proteins are completely hydrophilic and thus are present on the membrane
surface among the hydrophilic heads. The carbohydrate part of glycoproteins is hydrophilic and
protrudes outside the membrane. The pore of channel proteins is polar.
Explain the significance of polar and non-polar amino acids.
a.
b.
c.
d.
e.
f.
g.
h.
polar amino acids have hydrophilic R groups, non-polar have hydrophobic R groups;
distribution of amino acids influences the position of proteins in membranes ;
non-polar amino acids in centre of water-soluble proteins stabilise their structure;
non-polar amino acids cause proteins to remain embedded in membrane;
polar amino acids on surface of proteins make them water-soluble;
polar amino acids create hydrophilic channels/protein pores in membranes;
enzyme active site specificity depends on polarity of amino acids present and
nonpolar amino acids can play a role in substrate interactions at the active site as they
affect the tertiary and quarternary structure of proteins.
Outline four types of membrane transport, including their use of energy.
1. Simple diffusion is the passive movement of molecules / ions against a concentration
gradient
2. Facilitated diffusion is the passive movement of molecules / ions along a concentration
gradient through a protein channel without the use of energy. It is for those who cannot
pass through the phospholipid bilayer and the channel is specific.
3. Osmosis is the movement of membrane from a higher water potential to a lower water
potential down the water potential gradient through a passively permeable membrane.
4. Active transport is the movement of molecules / ions against the concentration gradient
through membrane pumps with the use of ATP / energy
5. Endocytosis is the infolding of membranes to bring molecules into the cell with the use of
energy.
6. Exocytosis is the infolding of membranes to release molecules from cell with the use of
energy
7. Chemiosmosis occurs when protons diffuse through ATP synthase in the membrane to
produce ATP.
State the property of amphipathic phospholipids that enables them to form a bilayer
They have both a hydrophilic and a hydrophobic region
Outline how vesicles are used to transport materials secreted by a cell.
a.
b.
c.
d.
e.
f.
g.
h.
vesicles formed from rER transport proteins to Golgi apparatus;
these vesicles fuse with membranes of Golgi apparatus;
proteins are processed as they move through Golgi apparatus;
transport vesicles bud off/leave Golgi apparatus;
vesicles move through cytoplasm;
vesicles fuse with plasma membrane;
contents released to outside of cell / exocytosis;
cells use vesicles to secrete substances such as hormones/digestive enzymes/other
appropriate example;
i. vesicles may contain cell products other than proteins;
Outline the effects of putting plant tissue in a hypertonic solution.
a. Hypertonic solution has a higher solute concentration than the tissue/cells/cytoplasm
b. Water moves out of the cells/tissue by osmosis «into the hypertonic solution»
c. Water moves from lower solute concentration to higher solute concentration/up the solute
concentration gradient
d. Pressure inside cell drops/cell no longer turgid/cell becomes flaccid
e. Volume of cytoplasm drops
f. «plasma» membrane retracts from the cell wall
g. cell is plasmolysed
Outline the cell cycle.
a. interphase is the longest phase; metabolically active phase between cell divisions
b. interphase includes G1, S and G2;
c. growth phase/G-1: synthesis of proteins/cytoplasm/organelles;
duplication of organelles
d. synthesis phase/S-phase: replication of DNA;
e. second growth phase/G-2: continued growth of cytoplasm/molecular synthesis/duplication of
organelles;
f. mitosis is when nucleus/genetic material divides;
g. prophase: chromosomes super-coil to prepare for mitosis / nuclear envelope disappears /
spindle fibres form;
h. spindle microtubules grow from poles to equator in prophase/metaphase;
i. nuclear membrane breaks down in prophase/metaphase;
j. spindle microtubules attach to the centromeres/chromosomes in metaphase;
k. metaphase: chromosomes line up at equatorial/metaphase plate
l. entromeres divide / paired chromatids separate / chromosomes separate into two chromatids in
metaphase/anaphase;
m. anaphase: chromatids move along microtubules/spindle fibres move sister chromatids toward
opposite poles;
n. shortening of sister chromatids
o. spindle microtubules disappear in telophase;
p. telophase: nuclear membranes form around each cluster of chromosomes;
q. chromosomes/chromatids decondense in telophase;
r. cytokinesis: the division of the cytoplasm / formation of two daughter cells
s. cytokinesis: new plasma membrane forms between the nuclei / cell plate forms;
t. a new cell wall forms;
u. mitosis results in two cells with identical nuclei
Explain how the cell cycle is controlled.
a. cell cycle is a sequence of stages / cell cycle is G1, S, G2 and mitosis
b. control of the cell cycle by cyclins/cyclin
c. levels of cyclins fluctuate during the cell cycle/surge at different times/have to reach a certain
concentration
d. conditions inside as well as outside the cell affect regulation
e. four cyclins/different cyclins to enter different stages of/events in the cell cycle / cyclins
regulate the sequence/timing of the cell cycle / cyclins trigger the next stages
f. cyclin-dependent kinases / cyclins bind to kinases and activate them
g. kinases phosphorylate other proteins
h. phosphorylated proteins perform specific functions in the cell cycle
State three processes occurring in a cell during interphase of the cell cycle but not in mitosis.
a. growth of cells;
b. transcription/protein synthesis/translation;
c. DNA replication / genetic material copied;
d. production of organelles/mitochondria/chloroplasts;
e. named normal activity of cell eg active transport, movement, secretion;
List two examples of how human life depends on mitosis.
a.
b.
c.
d.
e.
f.
growth/production of extra body cells;
first stage of spermatogenesis / forming oogonia/spermatogonia;
embryo development;
wound healing / tissue repair / hair growth / replacement of skin cells;
clonal selection / division of lymphocytes for antibody production;
asexual reproduction
Explain, using one example, how non-disjunction in meiosis can lead to changes in
chromosome number.
a. pair of homologous chromosomes moves in same direction/does not separate during anaphase
I / chromatids move in same direction/do not separate during anaphase II;
b. leaving a cell with an extra chromosome and another with a missing chromosome;
c. e.g. Down syndrome where there is an extra chromosome number 21
Chapter 2
Describe the importance of hydrolysis in digestion.
Digestion is the breakdown of large molecules into smaller molecules. This aids in making the
food soluble and allows it to be easily absorbed into the bloodstream and consequently into cells
of the body. Hydrolysis is the chemical breakdown of molecules due to their reaction with water.
Hydrolysis requires water and is aided by enzymes. Through hydrolysis, polysaccharides can be
hydrolysed to monosaccharide and disaccharides, proteins can be hydrolysed into amino acids
and triglycerides can be hydrolysed into fatty acids and glycerol. Later, these small molecules
can be joined to form the organism’s unique macromolecules.
Distinguish between anabolism, catabolism and metabolism.
Metabolism includes all of the enzyme-catalysed reactions in a cell or organism. It is anabolism
plus catabolism.
Anabolism is the synthesis of polymers or complex, large molecules from monomers or small,
simple molecules.
Catabolism is the breaking down of complex molecules into small, simpler ones or monomers.
State one disaccharide and the two monomers from which it can be synthesized.
Lactose
Glucose and Galactose
Maltose
Glucose and Glucose
Sucrose
Glucose and Fructose
Draw labelled diagrams to show a condensation reaction between two amino acids.
Compare and contrast cis-fatty acids and trans-fatty acids.
Both are unsaturated fatty acids and have two carbon atoms joined by a double bond.
In cis-fatty acids the two H atoms are on the same side while in trans-fatty acids they are on
opposite sides. Cis fatty acids are healthier than Trans fatty acids. Cis-fatty acids have a lower
boiling/melting point than trans fatty acids. Cis fatty acids have a kink in the chain but trans fatty
acids do not.
State the type of chemical reaction that occurs when lactose is digested into glucose and
galactose.
Hydrolysis
Suggest reasons for using lactase at relatively low temperatures.
The enzyme is less likely to denature and lasts longer. The reaction rate and products can also be
controlled. Further, it is economical as less energy is required to drive the reaction at low
temperatures.
For lactase, a lower temperature reduces bacterial growth and reduces milk spoilage.
State the functions of elements
Sulfur
It is a structural element in some amino acids, proteins and enzymes.
Calcium
It is a structural element in bones and teeth. It is a signal for cellular
processes. It triggers exocytosis.
Phosphorous
It is a structural element in ATP, DNA, RNA, phospholipids and in
bones.
Iron
It is required for the formation of hemoglobin, myoglobin and
cytochrome. Iron aids in the transport of oxygen.
Sodium
Potassium
Required for nerve impulse [sodium] and nerve transmission
[Potassium] and for the sodium-potassium pump and for
osmoregulation.
Describe cell respiration in terms of metabolism.
Cell respiration is metabolism because enzymes control the reactions. Energy is released from
complex molecules to make ATP. Respiration is catabolic and complex molecules become
smaller. C6H12O6 to CO2 + H2O
Outline the role of condensation and hydrolysis in the relationship between fatty acids,
glycerol and triglycerides.
Hydrolysis is the breakdown of larger molecules into smaller molecules with the addition of
water. Fatty acids are formed by the hydrolysis of triglycerides, wherein ester bonds are broken
and glycerol is released.
Condensation reactions are when molecules or subunits are joined to form a larger molecule. In
this reaction, water is formed and then removed, ester bonds are formed and up to three fatty
acids are linked to each glycerol.
Describe the importance of water to living organisms.
Water takes a lot of energy to evaporate and therefore is useful as a coolant. It is cohesive so it
can be pulled up and moved under tension in xylem. Due to its polarity, it is an excellent solvent
and dissolves many different substances which makes it an excellent medium for transport in
blood or xylem and phloem.
Water is also a medium for metabolic reactions which happen dissolved in water. Surface tension
due to cohesion allows organism to live on the water’s surface. A lot of organisms can also stride
across the water’s surface.
Water has a high heat capacity which means a lot of energy is required to change its temperature.
Ice floats so oceans do not freeze and animals living in water are able to continue life. Stable
habitat as the temperature changes very slowly. Water is used in chemical reactions,
photosynthesis and hydrolysis.
Its transparency is useful for photosynthesis and for vision in animals. Light passing through
water allows organisms to live beneath water.
Distinguish between active and passive movements of materials across plasma membranes,
using named examples.
Unlike active movement of materials, Passive movement of materials does not require energy or
any protein pumps. This is because the molecules pass down the concentration gradient.
Examples of this would be diffusion such as oxygen across alveoli , osmosis and facilitated
diffusion.
In active movement, the molecules pass across the concentration gradient and thus require ATP
as well as protein pumps. Examples of this would be exocytosis, pinocytosis, phagocytosis,
active transport for eg. glucose absorption in ileum and ion pumps.
Outline the role of proteins in active and passive transport of molecules through membranes.
a. channel proteins allow diffusion/osmosis/passive transport;
b. large/polar molecules cannot cross the hydrophobic membrane freely;
c. facilitated diffusion involves moving molecules through proteins down their concentration
gradient/without requiring ATP;
d. aquaporins specific integral membrane proteins facilitate the movement of water
molecules/osmosis;
e. some proteins for facilitated diffusion are specific to molecule/ions;
f. active transport involves moving molecules through proteins against their concentration
gradient/requiring ATP;
g. some proteins in the membrane are pumps / pumps perform active transport / sodium
potassium pump;
Compare simple diffusion with facilitated diffusion as mechanisms to transport solutes across
membranes.
Describe the structure and function of starch in plants.
Starch is a polysaccharide composed of glucose molecules. It contains amylose which is a linear
helical molecule, is less soluble and harder to digest. However, it takes less space than
amylopectin which starch is also made up of.
The function of starch is to store glucose / energy in starch and is particularly useful as it is a
storage form that does not draw water.
Describe the use of biotechnology in the production of lactose-free milk.
A particular yeast growing in natural milk contains lactase. This yeast can be cultured and the
enzyme lactase can be extracted from the yeast. Natural milk contains lactose and when added
directly to milk, lactase converts lactose into glucose and galactose. The same effect can be
achieved by milk being passed over immobilized lactase. Simpler forms of sugar glucose and
galactose can easily be absorbed by the small intestine.
The enzyme lactase is produced by the small intestine. Some people are lactose-intolerant and
cannot digest lactose in milk. A commerical market exists selling lactose-free milk. This milk is
sweeter than milk containing lactose. It has been ultrafiltered over immobilized beads to remove
lactose. This milk allows lactose-intolerant individuals to be nourished by milk without any
discomfort abdominal cramps / diarrhoea . Many asians are lactose-intolerant whereas this is less
common among other groups. Biotechnology produced in one part of the world may be useful in
another.
Explain how chemical bonding between water molecules makes water a valuable coolant in
living organisms.
Two water molecules are attracted to each other by intermolecular forces termed as “hydrogen
bonds”. These bonds are very strong. Breaking these bonds requires energy. These bonds must
break when water evaporates, and as heat is used to break the bond it makes the water as a
coolant for the organisms.
Describe four properties of water that are due to hydrogen bonding and polarity.
Hydrogen bonding causes it to have a high specific heat capacity requiring large energy to raise
the temperature, a high boiling point and cooling effect as hydrogen bonds need to be broken for
a change of state. Water molecules on the surface are resistant to foces due to the surface tension.
Water is more dense at 4 degrees celsius due to more regular hydrogen bonding.
Due to polarity, water molecules are cohesive and adhesive. They stick to each other through
cohesion which is useful in transport of water in xylem. They also stick to other polar molecules
through adhesion and are a good solvent of polar organic molecules.
Describe the movement of water across membranes.
Water moves across membranes by the process of osmosis. It passes from a region of high water
potential to a region of low water potential across a selectively permeable membrane.
Outline the role of water in photosynthesis.
Water molecules are split by light energy; this is known as photolysis. This process releases
hydrogen which helps to power the fixation of Carbon into organic molecules. Oxygen is formed
as a by-product.
Draw a second water molecule to show how bonds can form between water molecules,
including the name of the bond.
Oxygen of one molecules faces the hydrogen of another molecule. One hydrogen bond is drawn
as a dotted line b/w two water molecules.
Water has important solvent properties. Explain these properties using an example to illustrate
your answer.
Water molecules are polar with weak negative charges on the oxygen molecule and weak
positive charges on the hydrogen molecules. It formshydrogen bonds with polar substances. The
hydrogen side of water is attracted to negative ions. Sodium chloride dissolves in water as the
ions are attracted to water.
Outline the properties of water molecules that permit them to move upwards in plants.
Water molecules are polar and can form hydrogen bonds. Cohesion between water molecules
allows cotinuous water columns and allows a transpiration stream to form in xylem. Adhesion of
water to the walls of the xylem vessel helps it to rise. At environmental temperatures water
evaporates allowing a transpiration pull.
Distinguish between the thermal properties of water and methane.
Water has a higher melting points, a higher boiling point and a greater latent heat of vaporization
than methane.
Explain the reasons for the unique thermal properties of water.
Water is polar because of the oxygen atom being more negative and the hydrogen atom being
more positive. This causes strong hydrogen bonding between water molecules and these bonds
require more energy to break. These strong bonds thus increase the melting point, boiling point
and latent heat of vaporization of water.
Outline the production of a dipeptide by a condensation reaction, showing the structure of a
generalized dipeptide.
Condensation reactions nvolve the joining together of two amino acids in order to form a
dipeptide. The carboxyl group of one amino acid reacts with the amine group of another amino
acid causing water to be eliminated and a peptide bond to be formed. This reaction occurs at the
ribosomes. Many amino acids are joined together by condensation to form a polypeptide.
Functions of Proteins
Structural
Collagen / Membrane Proteins
Transport
Haemoglobin / Protein Channels
Movement
Actin / Myosin
Hormones
Insulin / Growth Hormone
Defense
Antibodies / Immunoglobins
Storage
Albumin
Other
DNA Packing / Histones / Catalyst / Enzyme
Amino acid polarity is an important factor in determining the functions of proteins. Explain
the importance of polar and non-polar amino acids in membrane proteins.
Polar amino acids are soluble in water, extracellular fluids and cytoplasm. Polar amino acids on
the surface of proteins make them water-soluble. On the other hand, non-polar amino acids are
soluble and have stable reactions in the lipid bilayer. They cause proteins to remain embedded in
membranes.
Polar amino acids are strongly hydrophilic and form hydrophilic channels or protein pores in the
membrane. Transmembrane proteins usually have polar amino acids on either side. Non-polar
amino acids are repelled by water and are hydrophobic.
Outline four different functions of membrane proteins.
a. receptor/binding site for hormone/neurotransmitter
b. cell-to-cell communication / cell recognition
c. channels «for passive transport» / facilitated diffusion
d. pumps / active transport
e. cell adhesion
f. «immobilized» enzymes/enzymes embedded in the membrane
g. electron transport / electron carriers
Discuss the relationship between one gene and one polypeptide.
DNA codes for a specific sequence of amino acids. The DNA code for one protein is a gene.
DNA is transcribed into mRNA. mRNA moves to a ribosome where it is translated into a
polypeptide. Originally it was thought that one gene always codes for a polypeptide. Some genes
do not code for a polypeptide. Some genes code for a transfer RNA and some sections of DNA
code for regulators that are not polypeptides. Change in the gene structure will affect the primary
structure of the polypeptide.
Describe the relationship between genes, polypeptides and enzymes.
gene is a sequence of DNA bases;
DNA/gene codes for a specific sequence of amino acids/polypeptide;
enzymes are proteins/composed of polypetides;
sequence of amino acids determines tertiary structure/folding/shape of active site;
change in the gene/mutation will affect the active site/function of an enzyme;
enzymes are involved in replication/transcription of genes;
enzymes are involved in synthesis of polypeptides;
Describe the genetic code and its relationship to polypeptides and proteins.
a. the genetic code is based on sets of three nucleotides/triplets of bases called codons;
b. bases include adenine, guanine, cytosine and thymine in DNA / adenine, guanine, cytosine and
uracil in RNA; do not accept ATCG
c. each codon is code for one amino acid;
d. some codons are start or stop codons;
e. DNA is transcribed into mRNA by base-pair matching/complementary base pairing;
f. mRNA is translated into a sequence of amino acids/polypeptide;
g. each gene codes for a polypeptide;
h. polypeptides may be joined/modified to form proteins;
Distinguish between fibrous and globular proteins with reference to one example of each
protein type.
Fibrous are strands/sheets
Globular are rounded
Insoluble
Soluble
Less sensitive to pH, temperature and salts
More sensitive
Structural roles
Catalysis / Transport
Keratin/fibrin/collagen/actin/myosin/silk
protein
Insulin/immunoglobulin/hemoglobin
Describe how the tertiary protein structure relates to enzyme function.
Tertiary is the specific 3D structure giving rise to the specific shape of the active site. The
tertiary structure enables enzymes to bind effectively to substrate. It determines whether some
enzymes have broad or narrow specificity. Inhibitors can affect tertiary structure and thus
function.
Chapter 7
Explain why DNA must be replicated before mitosis and the role of helicase in DNA
replication.
two genetically identical nuclei/daughter cells formed during mitosis so hereditary information in
DNA can be passed on ;
two copies of each chromosome/DNA molecule/chromatid needed;
helicase unwinds the DNA/double helix;
to allow the strands to be separated;
helicase separates the two complementary strands of DNA;
by breaking hydrogen bonds between bases;
Explain how the base sequence of DNA is conserved during replication.
DNA replication is semi-conservative;
DNA is split into two single/template strands;
nucleotides are assembled on/attached to each single/template strand;
by complementary base pairing;
adenine with thymine and cytosine with guanine / A with T and C with G;
strand newly formed on each template strand is identical to other template strand;
DNA polymerase used;
Outline the bonding between DNA nucleotides.
Hydrogen bonds between nucleotides of opposite strands/complementary bases/adenine and
thymine and cytosine and guanine;
Covalent bonds between nucleotides within strands/between sugar/deoxyribose and phosphate;
Functions of DNA:
a. regulate gene expression
b. act as promoter
c. role in chromosome pairing/crossing over/recombination
d. introns
State a chemical modification of a nucleosome that could impact gene expression.
methylation/acetylation/phosphorylation/epigenetic tags/modification of nucleosome
tails/N-terminal tails
Distinguish between semi-conservative replication and conservative replication.
Explain the pattern shown in generation 3.0.
As replication is semi-conservative each new strand is built on parental/old/template strand
Generation 3 shows DNA that is mostly made of 14N
When E. coli replicates, half of its new DNA must always contain 14N when growing in a 14N
growth medium
Every new generation of E. coli always has a smaller proportion of labelled 15N in its DNA than
the previous generation
Each new generation has half the amount of 15N in previous generation
Explain how the base sequence of DNA is conserved during replication.
a.
b.
c.
d.
e.
f.
g.
DNA replication is semi-conservative;
DNA is split into two single/template strands;
nucleotides are assembled on/attached to each single/template strand;
by complementary base pairing;
adenine with thymine and cytosine with guanine / A with T and C with G;
strand newly formed on each template strand is identical to other template strand;
DNA polymerase used;
Explain the significance of complementary base pairing for replication, transcription and
translation.
a. A-T and C-G in DNA;
b. A-U and C-G in RNA;
c. complementary base pairing in replication ensures identical nucleotide sequence of new
complementary strands;
d. semi-conservative replication;
e. transcription produces RNA sequence complementary to the DNA sequence of the gene ;
f. triplets of nucleotides on mRNA are codons;
g. translation converts mRNA sequence of information into a specific amino acid chain
polypeptide ;
h. each class of tRNA carries a specific triplet of three bases called an anticodon;
i. anticodons bind to codons by complementary base pairing;
j. each class of tRNA with specific complementary anticodons carry specific amino acids;
k. sequence of mRNA codons translates into specific amino acid sequence;
l. enables conservation of information transfer from DNA to RNA to polypeptide;
Explain why DNA must be replicated before mitosis and the role of helicase in DNA
replication.
a. two genetically identical nuclei/daughter cells formed during mitosis so hereditary
information in DNA can be passed on ;
b. two copies of each chromosome/DNA molecule/chromatid needed;
c. helicase unwinds the DNA/double helix;
d. to allow the strands to be separated;
e. helicase separates the two complementary strands of DNA;
f. by breaking hydrogen bonds between bases;
Explain the roles of specific enzymes in prokaryote DNA replication.
a.
b.
c.
d.
e.
DNA gyrase/topoisomerase I prepares for uncoiling/relieves strains in the double helix
Helicase uncoils/unwinds the DNA/double helix
Helicase separates/unzips/breaks hydrogen bonds between the two strands of DNA
DNA primase adds an RNA primer/short length of RNA Accept RNA primase.
DNA polymerase III adds DNA nucleotides/replicates DNA/synthesizes complementary
strand in a 5’ to 3’ direction
f. DNA polymerase III starts replication/adding nucleotides at the primer
g. DNA polymerase I removes the primer/replaces RNA with DNA
h. DNA ligase seals the nicks
links sections of replicated DNA
links Okazaki fragments
i. DNA polymerase I/DNA polymerase III proofreads for mistakes
Growth in living organisms includes replication of DNA. Explain DNA replication.
a. occurs during S phase of interphase/in preparation for mitosis/cell division;
b. DNA replication is semi-conservative;
b. each molecule formed has one new strand and one from parent molecule;helicase unwinds the
double helix
b. gyrase/topoisomerase relieves strains during uncoiling
c. helicase separates the two strands of DNA/breaks hydrogen bonds
d. each single strand acts as a template for a new strand / process is semi-conservative
e. DNA polymerase III can only add nucleotides to the end of an existing chain/to a primer
e. RNA primase adds primer / primase adds short length of RNA;
f. DNA polymerase III binds to/starts at RNA primer;
g. DNA polymerase III adds nucleotides/bases in a 5’ → 3’ direction;
h. bases according to complementary base pairing / A–T and C–G;
i. leading strand built up continuously towards the replication fork;
j. lagging strand built up in pieces/short lengths/Okazaki fragments;
k. DNA polymerase I removes RNA/primers and replaces them with DNA;
l. ligase seals gaps between nucleotides/fragments/makes sugar-phosphate bonds;
m. replication only occurs at a single replication fork;
n. nucleoside triphosphates provide the energy to add nucleotides
o. ligase joins the fragments together/seals the nicks
p. as deoxynucleoside triphosphate joins with growing DNA chain, two phosphates broken off
releasing energy to form bond;
Outline the structure and functions of nucleosomes.
a. found in eukaryotes;
b. consists of DNA wrapped around proteins/histones;
c. histones are in an octamer/group of eight;
d. are held together by another histone/protein;
e. in linker region;
f. help to supercoil chromosomes / to facilitate DNA packing;
g. function is to regulate transcription / gene expression;
Explain how DNA is used to pass on genetic information to offspring accurately but also
produce variation in species.
a. DNA is replicated/copied semi-conservatively/from a template;
b. mutations can be a source of variation / resulting protein has new or different functions;
c. mutations/changes in the DNA may not result in changes in the amino acid for which the
triplet codes;
d. genetic code is redundant;
e. genes occur as paired alleles which can be different;
f. crossing-over occurs;
g. recombines linked alleles producing new combinations;
h. random orientation of bivalents / homologous chromosomes in metaphase I ;
i. large genetic variation in haploid gametes / 2n / 223;
j. random recombination of alleles during fertilization leads to variation ;
k. different phenotypes among members of the same population;
l. natural selection may lead to enhanced survival of recombinants;
Distinguish between the sense and antisense strands of DNA during transcription.
Only the antisense strand is transcribed / the antisense strand is transcribed to mRNA and the
sense strand is not transcribed/has the same base sequence as mRNA with uracil instead of
thymine
Explain the role of Okazaki fragments in DNA replication.
DNA fragments/sections formed on the lagging strand;
because replication must be in the 5' –3' direction;
replication starts repeatedly and moves away from replication fork;
Outline the structural and genetic characteristics of eukaryotic chromosomes
A chromosome is a linear DNA molecule two DNA molecules after replication .
Explain the methods and aims of DNA profiling.
DNA sample obtained from hair/blood/semen/human tissue;
Quantity of DNA increased by PCR/polymerase chain reaction;
highly repetitive sequences are used/amplified;
DNA cut into fragments;
using restriction enzymes/restriction endonucleases;
electrophoresis involves electric field/placing sample between electrodes;
used to separate DNA fragments according to size;
creating DNA profiles/unique patterns of bands;
comparison is made between the patterns;
number of repeats varies between individuals / pattern of bands is unique to the
individual/unlikely to be shared;
criminals/victims can be identified in this way;
DNA obtained from the crime scene/victim compared to DNA of suspect / other example of
forensic use;
DNA is quite stable / DNA can be processed long after the crime;
paternity testing use e.g. DNA obtained from parents in paternity cases;
biological father if one half of all bands in the child are found in the father;
genetic screening;
presence of particular bands correlates with probability of certain phenotype / allele;
other example;
brief description of other example;
a. PCR is process by which a small sample of DNA can be amplified/copied many times
b. PCR involves repeated cycling through high and lower temperatures to promote melting and
annealing of DNA strands
c. mixture is heated to high temperatures to break hydrogen bonds between strands of DNA/to
separate the double-stranded DNA
d. Taq DNA polymerase can withstand high temperatures without denaturing
e. primers bind to targeted DNA sequences at lower temp
f. Taq DNA polymerase forms new double-stranded DNA by adding complementary
bases/nucleotides when cooling
g. with the use of DNA polymerase and primers ;
h. process/heating and cooling cycle is repeated until enough DNA is obtained ;
Distinguish between the structures of DNA and RNA
Physical: DNA is double stranded whereas RNA is single stranded
DNA always has a helical structure, whereas RNA an come in varied forms, eg. mRNA, tRNA
and rRNA
Chemical: DNA contains deoxyribose and RNA contains ribose which has one extra oxygen
molecule
The four nitrogenous bases of DNA are adenine, thymine, cytosine and guanine whereas RNA
has uracil in place of thymine
Most of the DNA of a human cell is contained in the nucleus. Distinguish between unique and
highly repetitive sequences in nuclear DNA.
satellite DNA is repetitive;
repetitive sequences are used for profiling;
prokaryotes do not usually contain repetitive sequence
Distinguish between transcription and translation.
a. DNA is transcribed and mRNA is translated
b. transcription produces RNA AND translation produces polypeptide/protein
c. RNA polymerase used in only in transcription and ribosomes only in translation
d. transcription in the nucleus of eukaryotes and translation in the cytoplasm
e. tRNA needed for translation but not transcription
f. nucleotides linked in transcription and amino acids in translation
sugar-phosphate/phosphodiester bonds in transcription and peptide bonds in translation
Explain the control of gene expression in eukaryotes.
a. mRNA conveys genetic information from DNA to the ribosomes where it guides polypeptide
production
b. gene expression requires the production of specific mRNA through transcription
c. most genes are turned off/not being transcribed at any one time/regulated
some genes are only expressed at certain times
d. some genes are only expressed in certain cells/tissues
cell differentiation involves changes in gene expression
e. transcription factors/proteins can increase/decrease transcription
f. hormones/chemical environment of cell can affect gene expression
g. example of cell environment
eg: auxin/insulin/cytoplasmic gradient in embryo
h. transcription factors/proteins may prevent or enhance the binding of RNA polymerase
i. nucleosomes limit access of transcription factors to DNA/regulate gene
expression/transcription
activate or silence genes
j. DNA methylation/acetylation appears to control gene expression as epigenetic factor
methylated genes are silenced
k. some DNA methylation patterns are inherited
l. introns may contain positive or negative gene regulators
gene expression can be regulated by post-transcriptional modification/splicing/mRNA processing
Explain the process of transcription in prokaryotes.
a. transcription, synthesis of RNA identical to one coding strand of DNA;
antisense stand acts as template/is transcribed;
b. RNA polymerase attaches to sequence of DNA known as promoter region ;
c. RNA polymerase separates the two strands of DNA;
d. unwinding exposes 10–20 DNA bases for pairing with RNA nucleotides;
e. RNA nucleotides matched to complementary bases;
f. adenine with uracil and cytosine with guanine / uracil replaces thymine;
g. H bonds between RNA nucleotide and complementary base on DNA strand;
h. RNA nucleoside triphosphates used;
i. binding nucleoside triphosphates to the antisense strand of DNA;
j. hydrolysis of two phosphate molecules provides energy for reaction;
k. adds nucleotides to the 3′ end of RNA molecule/in 5′ → 3′ direction;
l. terminator is sequence of DNA signaling end of transcription;
m. RNA polymerase detaches from the DNA;
n. many RNA polymerases can follow each other;
o. introns have to be removed in eukaryotes to form mature mRNA;
Outline the roles of the different binding sites for tRNA on ribosomes during translation.
a. A, P and E binding sites are on the large subunit of the ribosome
b. initiation of translation starts with binding of met-tRNA to the start codon
c. large sub-unit binds with start tRNA in the P site
d. A binding site holds the tRNA with the next amino acid to be added
e. peptide bond is formed between the amino acids of the A site and the polypeptide at the P site
f. polypeptide is transferred to the tRNA in the A site
g. the tRNA with polypeptide in A site then moves to P site
P binding site holds the tRNA attached to the growing polypeptide
h. E binding site exit is where the tRNA from P site without amino acid leaves the ribosome
Protein structures:
Primary structure is sequence of amino acids joined by peptide bonds;
Tertiary structure is the folding of the polypeptide/secondary structure/alpha helix;
stabilized by disulfide/ionic/hydrogen bonds/hydrophobic interactions;
tertiary structure gives three dimensional globular shape/shape of active site;
Quaternary structure is the linking of two or more polypeptides to form one protein;
State what is indicated by the presence of polysomes in a cell.
Polysomes are groups of ribosomes that are translating the same mRNA, which indicates that the
cell needs multiple copies of one particular polypeptide.
much protein of one type needed/produced by polysomes;
mRNA is being repeatedly translated;
Alpha helix is held together by:
hydrogen bonds;
between the turns of the helix rather than between R-groups ;
bonds between carboxyl and NH groups/C-O---H-N;
Role of tRNA:
tRNA attaches to specific amino acid;
tRNA with amino acid moves to the ribosome;
anticodon of tRNA binds with codon of mRNA;
Outline how translation depends on complementary base pairing.
a. translation converts a sequence of mRNA nucleotides/codons to a sequence of amino
acids/polypeptide/protein
b. triplets of nucleotides/bases on activated tRNAs pair with complementary triplets of
nucleotides/bases on mRNA / vice versa
c. base pairing occurs when adenine/A pairs with uracil/U and guanine/G pairs with cytosine/C
d. specific amino acids are attached to specific of tRNA
e. mRNA has codons and tRNA has anticodons
Outline how the structure of the ribosome is related to its function in translation.
translation is protein/polypeptide synthesis;
a small subunit and a large one;
formed by ribosomal RNA and proteins in both subunits; both needed
about 20nm/30nm / 80S in eukaryotes;
70S in prokaryotes / 80S in eukaryotes;
can be free / bound to RER in eukaryotes ;
organized into a tertiary structure/globular shape;
three binding sites for tRNA on/in large subunit;
Aminacyl/A, Peptidyl/P and Exit/E;
binding site for mRNA on surface/in small subunit;
two tRNA can bind at the same time;
ribosomal RNA catalyses formation of peptide bond;
Role of ribosomes:
a. translation is the production of polypeptides/proteins
b. mRNA binds to the ribosome
c. tRNA binds to the ribosome
d. at the site where its anti-codon corresponds to the codon on the mRNA
e. amino acids of consecutive tRNAs bind by a peptide link in the ribosomes
f. the ribosome moves along the mRNA
continues with elongation of polypeptide chain.
Outline the differences between these two proteins.
a. hemoglobin is a globular protein while keratin is a fibrous protein;
b. hemoglobin folds into rounded structures while keratin remains linear;
c. hemoglobin is a soluble protein while keratin is not;
d. hemoglobin consists of four peptides/subunits while keratin does not;
e. hemoglobin has prosthetic/heme groups while keratin does not;
f. hemoglobin functions as transport molecule while keratin is a structural molecule/part of
hair/nails;
Translation occurs in living cells. Explain how translation is carried out, from the initiation
stage onwards.
a. translation involves initiation, elongation/translocation and termination;
b. translation is the synthesis of proteins/polypeptide chain/specific sequence of amino
acids;
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
o.
p.
q.
r.
s.
t.
u.
v.
w.
x.
y.
z.
translation occurs in cytoplasm/ribosomes;
uses information on the mRNA;
mRNA carries the genetic information of DNA;
mRNA binds to ribosome;
mRNA contains series of codons/base triplets;
mRNA 5’ binds to the small sub-unit of the ribosome;
ribosome slides along mRNA to the start codon AUG
anticodon of tRNA pairs with codon on mRNA:
complementary base pairing between codon and anticodon ;
tRNA carries the amino acid methionine
anticodon of tRNA with methionine pairs with start codon
large ribosome subunit aligns then tRNA is at p-site and forms complex w small subunit
second tRNA pairs w next codon in the A-site
peptide bond forms between amino acids in A-site and P-site
ribosome moves along the mRNA by one codon;
movement in 5' to 3' direction;
tRNA that has lost its amino acid detaches and leaves through the P-site
A-site one goes to the P-site
another tRNA pairs with the next codon/moves into A site;
polypeptide chain gets synthesized
multiple rna do single mrna sequence and group of ribosome = polysome
tRNA activating enzymes link amino acids to specific tRNA;
ribosome eventually reaches the stop codon
release factors enzymes release the polypeptide
Chapter 8
Compare competitive and non-competitive enzyme inhibition
Both competitive and non-competitive enzyme inhibition slow down reaction rate.
In competitive enzyme inhibition, the inhibitor is similar to the substrate molecule. Therefore it
binds to the active site of the enzyme thereby preventing the substrate to bind to it. Increasing the
substrate concentration would diminish the effect of the inhibitor as the substrate would be more
likely to bind to the active site. An example would be succinate dehydrogenase inhibited by
malonate.
In non-competitive enzyme inhibition, the inhibitor is usually different from the substrate. It
binds to an allosteric site away from the active site. By doing so, it changes the shape of the
active site thereby preventing the substrate from binding to it. A change in substrate
concentration would not diminish the inhibition as the active site would still be different in
shape. An example would be respiratory enzymes inhibited by cyanide.
Outline the control of metabolism by end-product inhibition
A metabolic pathway is a chain of enzyme-catalysed reactions. The end product inhibitor which
is always the final product of the metabolic pathway inhibits the first enzyme in the pathway. It is
an example of non-competitive inhibition, as the end product inhibitor binds to an allosteric site
of the enzyme a site away from the active site .
By binding to the allosteric site, it changes the shape of the active site. End-product inhibition
prevents intermediates from building up, prevents formation of excess product as it switches off
the whole metabolic pathway. The binding of the end product is reversible and the pathway
restarts if the enf product detaches.
An example of end-product inhibition would be the threonine to isoleucine pathway. The end
product threonine binds to the first enzyme isoleucine when a sufficient amount of isoleucine has
been produced.
Outline how enzymes catalyse reactions.
Enzymes increase the rate of chemical reactions and remain unchanged at the end of the reaction.
They lower the activation energy of the reaction. Activation energy is needed to overcome the
energy barrier that prevents the reaction. The substrate bonds to an active site on the enzyme to
form an enzyme-substrate complex. The substrate binding to the enzyme brings reactants closer
to facilitate chemical reactions. The formation of an induced-fit model or change in enzyme
conformation makes the substrate more reactive. The enzyme changes shape once bound /
enzyme moulds to substrate/ hand in glove. The change in shape strains bonds/facilitates bonds
breaking/product formation;
Outline the importance of enzymes to metabolic processes.
Enzymes increase the rate of reaction. A specific enzyme exists for every reaction. If an enzyme
is inhibited or absent, the metabolic pathway is blocked. End-product inhibition can control
metabolic pathways. Cells produce different enzymes during differentiation causing differences
in metabolism.
Explain why oxygen consumption is used as a measure of metabolic rate.
Oxygen is used for aerobic respiration which releases ATP. Metabolism is the measure of total
energy produced and consumed by the body. Oxygen consumption is proportional to metabolic
rate.
Distinguish between anaerobic and aerobic cell respiration in eukaryotes.
Many cell functions, like synthesis of macromolecules and transport, require energy in the
form of ATP. Explain how ATP is generated in animal cells.
a. ATP is a form of energy currency/immediately available for use;
b. ATP is generated in cells by cell respiration from organic compounds ;
c. aerobic cell respiration requires oxygen;
d. anaerobic cell respiration does not require oxygen;
e. glycolysis breaks down glucose into pyruvate;
f. glycolysis occurs in cytoplasm;
g. by glycolysis a small amount of ATP is released;
h. ADP changes into ATP with the addition of a phosphate group/phosphoric acid / accept as
chemical equation;
i. in mitochondria/aerobic respiration produces large amount of ATP / 38 mols for the cell, per
glucose molecule ;
j. oxygen/aerobic respiration is required for mitochondrial production of ATP;
k. in mitochondria/aerobic respiration pyruvate is broken down into carbon dioxide and water;
Explain the process of aerobic cell respiration after glycolysis has occurred.
The pyruvate formed in glycolysis enters the mitochondrial membrane. It undergoes the link
reaction and is decarboxylated, losing CO2and NADH + H+. Acetyl CoA is formed which will
take part in the Kreb’s cycle, in which 2 molecules of CO2, one molecule of ATP from ADP +
Pi, one molecule of FADH and three molecules of NADH+H+ for every molecule of pyruvate.
The NADH+H+ provides electrons circulating in the electron transport chain on the inner
mitochondrial membrane, allowing H+ to accumulate in the intermembrane space and come back
to the matrix through ATP synthase to produce ATP through chemiosmosis. The presence of O2
required as the final electron acceptor for the electron transport chain produces water with H+.
The protein hemoglobin transports oxygen to cells. Describe the processes that occur in the
mitochondria of cells when oxygen is present.
When pyruvate enter the mitochondrion, it is decarboxylated and NADH+H+ is formed. A
two-C molecule reacts with reduced coenzyme A to form acetyl CoA. Acetyl CoA enters the
Kreb’s cycle. 2 CO2 molecules are removed as waste. Electron-rich NADH+H+ and FADH2 are
formed. For each pyruvate, 3 NADH+H+ and 1 FADH2 are formed as well as one ATP
molecule. Reduced NADH+H+ and FADH2 enter electron transport chain.
Oxidative phosphorylation uses energy released by ETC to synthesise ATP. As electrons move
across the ETC, H+ moves into the intermembrane space. It creates an H+ gradient across the
membrane allowing H+ to come back to the matrix through ATP synthase to produce ATP
through chemiosmosis. The presence of O2 required as the final electron acceptor for the
electron transport chain produces water with H+.
Explain how chemical energy for use in the cell is generated by electron transport and
chemiosmosis.
a. NAD/FAD carries/is reduced by gaining two H atoms / two electrons
b. reduced NAD produced in glycolysis/link reaction/Krebs cycle
c. reduced NAD/FAD delivers electrons/hydrogen atoms to ETC
d. ETC is in mitochondrial inner membrane/cristae
e. electrons release energy as they flow along the chain/from carrier to carrier
f. electrons from ETC accepted by oxygen/oxygen is the final electron acceptor
g. proteins in the inner mitochondrial membrane/electron carriers act as proton pumps
h. protons pumped into intermembrane space/proton gradient across inner mitochondrial
membrane/proton concentration higher in intermembrane space than in matrix
i. energy from electrons used to pump protons into intermembrane space/generate a proton
gradient / high H+ concentration is a store of potential energy
j. ATP synthase in inner mitochondrial membrane/cristae
k. energy released as protons pass down the gradient/through ATP synthase
l. ATP synthase converts ADP to ATP/phosphorylates ADP
m. oxidative phosphorylation is ATP production using energy from oxidizing foods
Some of the water carried to the leaves of a plant is used in photosynthesis. Explain the role of
water in the light-dependent reactions of photosynthesis.
In terms of the light-dependent reactions of photosynthesis, water only plays a role in non-cyclic
phosphorylation. Chlorophyll absorbs light energy and activates the electrons of Photosystem II.
This is known as photoactivation. These active electrons from Photosystem II are passed to
carriers. Photolysis is the splitting of water and it forms O2 and H+. O2 is released as waste
while the electrons produced by the splitting of water replace the electron lost in photoactivation.
The electrons from photosystem II pass through carriers to photosystem I. The electrons from
photosystem I pass to NADP+ in stroma. The NADP+ accepts the H+ from water to form
NADPH. The electron flow also causes protons pumped across the thylakoid membrane into the
thylakoid space creating a proton concentration gradient. Chemiosmosis couples electron
transport to ATP synthesis and protons pass through ATP synthase. The NADPH is passed to the
light-independent reactions to fix carbon.
During photosynthesis plants use water in the conversion of light energy to chemical energy.
This is called photolysis / light-dependent reactions / photophosphorlyation. Explain how
water is used in photosynthesis.
The light energy is used to split water into H+ ions, electrons and oxygen. The electrons from the
water are used to replace the ones released during photoactivation the electron that was lost from
Photosystem II . This allows for the process to continue as the electron has been replaced and
thus when excited it will continue to pass down the electron transport chain. As the electron
flows down the electron transport chain, it releases energy which pumps hydrogen ions from the
photolysis of water across the thylakoid membrane to produce an electrochemical gradient.
Explain the relationship between the absorption spectrum for chlorophyll and action spectrum
of photosynthesis for green plants.
a.
b.
c.
d.
light/photon absorbed by pigment molecules in photosystem II /chlorophyll;
energy/electrons passed to chlorophyll molecule at the reaction centre;
causes electron to be raised to higher energy level / electron is excited;
this electron passed along chain of carrier molecules in photosystem II;
Explain how chemiosmosis assists in ATP production during oxidative phosphorylation.
Chemiosmosis occurs during aerobic reactions. Oxidative phosphorlyation occurs during the
electron transport chain. Hydrogen is passed between carriers releasing energy. The electron
finally joins with oxygen to form water in the cristae of the mitochondria. Chemiosmosis is the
movement of hydrogen ions against the concentration gradient into the space between the two
membranes. The protons flow back to the matrix through the ATP synthase. Energy is released
which produces more ATP by combining ADP and Pi.
Explain the process of photophosphorylation in chloroplasts.
e. using energy from light to provide energy;
f. absorbing light/photoactivation produces an excited/high energy/free electron;
g. absorption of light in photosystem II gives electron to chain of carriers;
photolysis;
h. H+ pumped across thylakoid membrane;
i. protons pass through ATP synthetase/synthase;
j. producing ATP;
k. chemiosmosis;
l. chlorophyll/antenna of photosystem I absorbs light;
m. cyclic and non-cyclic photophosphorylation;
n. in non-cyclic photophosphorylation photolysis of water produces H+/O2/e–;
o. in cyclic photophosphorylation electron returns to photosystem I;
Explain chemiosmosis as it occurs in photophosphorylation.
a. photophosphorylation is the production of ATP;
b. some of the light absorbed by chlorophyll / photosystem II;
c. photolysis/splitting of water separation of hydrogen ion from its electron;
d. the electron transport system moves the electrons through a series of carriers;
e. electron transport system occurs in the thylakoid membrane;
f. electron transport linked to movement of protons into thylakoid space;
g. a proton gradient builds up in the thylakoid space ;
h. small thylakoid space enhances the gradient;
i. hydrogen ions move by diffusion through the ATP synthase;
j. ADP + inorganic phosphate Pi forms ATP;
k. the kinetic energy from movement of hydrogen ions through ATP synthase generates ATP;
l. ATP synthase is a protein complex in the thylakoid membrane;
m. formation of proton gradient / ATP synthesis linked to electron transport is chemiosmosis;
Outline the light-dependent reactions of photosynthesis.
a. chlorophyll/pigments/antenna complex in photosystem II absorb light;
b. light/photoactivation produces an excited/high energy/free electron;
c. electrons pass from carrier to carrier/along electron transport chain/e.t.c.;
d. protons pumped across thylakoid membrane/into thylakoid space;
e. ATP produced by the light dependent reactions ;
f. ATP production by chemiosmosis/by ATP synthase/ATP synthetase;
g. electrons from photosystem II passed to photosystem I;
h. light/photoactivation excites electrons in photosystem I to higher energy level ;
i. production of NADPH/reduction of NADP + using electrons from photosystem I ; reject NAD
in place of NADP. Accept reduced NADP instead of NADPH
j. electrons from photolysis needed for photosystem II;
k. oxygen from photolysis is a waste product/by-product/passes out/excreted;
l. in cyclic photophosphorylation electrons from photosystem I return to it;
Explain the light-independent processes of photosynthesis in plants.
a. occurs in stroma of chloroplast ;
b. energy/ATP and NADPH provided by the light-dependent reactions;
c. Calvin cycle;
d. carbon dioxide fixed to RuBP / carboxylation of RuBP/ribulose bisphosphate;
e. by RuBP carboxylase/rubisco;
f. forms unstable 6C compound / forms 6C compound which splits;
g. glycerate 3-phosphate is produced by carbon fixation ;
h. glycerate phosphate to triose phosphate/3C sugar by reduction/adding hydrogen;
i. using NADPH/reduced NADP;
j. triose phosphate/3C sugar converted to form hexose/glucose phosphate ;
k. most/5/6 of triose phosphate used for regeneration of RuBP;
l. ATP used to regenerate RUBP/convert glycerate 3-phosphate to triose phosphate;
Explain the role of cristae in mitochondria.
a. increase the surface area of inner mitochondrial membrane; note: mitochondria is in the stem
b. allow electron transport because of embedded protein electron carriers;
c. facilitate proton pumping because of high surface to volume ratio/increased surface area;
d. increase ATP production because of ATP synthase/synthatase embedded in membrane;
Outline the process of glycolysis.
a.
b.
c.
d.
e.
f.
g.
occurs in cytoplasm
hexose is phosphorylated using ATP;
hexose phosphate is split into two triose phosphates;
oxidation by removal of hydrogen; do not accept hydrogen ions/protons
conversion of NAD to NADH +H+ ;
net gain of two ATP / two ATP used and four ATP produced;
pyruvate produced at the end of glycolysis;
Outline the process of aerobic respiration.
a.
b.
c.
d.
e.
f.
g.
h.
during glycolysis glucose is partially oxidized in the cytoplasm;
small amount/yield of ATP produced;
two pyruvate formed by glycolysis;
pyruvate absorbed into/broken down in the mitochondrion;
requires oxygen;
carbon dioxide is produced;
water is produced;
large amount/yield of energy/ATP molecules per glucose molecule ;
Explain the link reaction that occurs between glycolysis and the Krebs cycle.
a.
b.
c.
d.
e.
f.
g.
h.
pyruvate from glycolysis enters a mitochondrion;
enzymes in the matrix remove one carbon dioxide and hydrogen from the pyruvate;
hydrogen is accepted by NAD/forms NADH;
removal of hydrogen is oxidation;
removal of carbon dioxide is decarboxylation;
the whole process/link reaction is oxidative decarboxylation;
the product is an acetyl group which reacts with CoA/coenzyme A;
acetyl CoA enters Krebs cycle;
Explain the processes by which light energy is converted into chemical energy.
a. plants/producers/autotrophs convert light to chemical energy by photosynthesis
b. chlorophyll/photosynthetic pigments absorb light
c. electrons are excited/raised to higher energy level
d. excited electrons pass along chain of electron carriers
e. energy from electrons used to pump protons across thylakoid membrane/into thylakoid space
f. chemiosmosis/proton gradient used to make ATP
g. ATP synthase generates ATP
h. pigments arranged in photosystems
i. electrons from Photosystem II flow via the electron chain to Photosystem I
j. electrons from Photosystem I are used to reduce NADP
k. ATP and reduced NADP used in the light independent reactions/Calvin cycle
l. carbohydrate/glucose/carbon compounds produced containing energy
Explain how any two structural features of the mitochondrion are related to its function.
Cristae for increasing surface area and a small inter-membrane space for rapid build-up of
concentration gradient. A matrix with chemical concentration to support unique chemical
reactions. Matrix has enzymes for Kreb’s cycle/Link reaction. ATP synthase generates ATP from
ADP + Pi. DNA for protein synthesis and replication. ETC for generating a proton gradient.
LDR happen on the stroma of the chloroplast. Explain the relationship between the structure
of the chloroplast and its function.
Thylakoids have a large surface area for light absorption. Thylakoids also have a small space for
the accumulation of protons and a fluid stroma for enzymes in Calvin cycle / the
light-independent reactions. The arrangement of photosystems allow the electron transport to
take place. The double membrane on the outside allows for separation from the cell. Chloroplast
also has DNA and ribosomes present for protein synthesis. Starch grains store carbohydrates
from photosynthesis.
Distinguish between absorption of red, green and blue light by chlorophyll.
Blue and red light are absorbed in high amounts by chlorophyll, with blue light being absorbed at
a comparatively greater amount. Green light is reflected.
​Chapter 3 and 10
Outline the processes that occur during the first division of meiosis.
a. (consists of) prophase, metaphase, anaphase and telophase;
b. chromosome number halved/reduced/(diploid) to haploid;
c. homologous chromosomes pair up/form a bivalent/synapsis in prophase;
d. crossing over between non-sister chromatids/chromatids of different
homologues;
e. nuclear envelope breaks down (at end of prophase/start of metaphase);
f. tetrads/bivalents/homologous pairs move to/align on equator/cell centre/on
metaphase plate in metaphase; (accept homologous chromosomes without pairs if
pairing has already been described)
g. attachment of spindle fibres/microtubules to centromeres/kinetochores;
h. (homologous) chromosomes separate/pulled to opposite poles in anaphase;
i. nuclear envelopes reform/do not reform (because of meiosis II) in telophase;
Outline outcomes of the human genome project.
a. complete human DNA/chromosomes sequenced;
b. identification of all human genes / find position/map (all) human genes on
chromosomes
c. find/discover protein structures/functions;
d. find evidence for evolutionary relationships/human origins/ancestors;
e. find mutations/base substitutions/single nucleotide polymorphisms;
f. find genes causing/increasing chance of/develop test for/screen for diseases;
g. develop new drugs (based on base sequences) / new gene therapies;
h. tailor medication to individual genetic variation / pharmacogenomics;
i. promote international co-operation/global endeavours;
j. knowledge of the base sequence of genes/study of variation within genome;
Distinguish between the terms genotype and phenotype.
Genotype is the genetic make-up/set of alleles (of an organism) while phenotype is
the characteristics (expressed/shown in an organism)
Outline a structural difference between the chromosomes of Helicobacter pylori
and Homo sapiens.
Chromosome from bacteria has no protein associated/naked DNA / bacteria is
circular, H. sapiens is linear / (chromosomes of) H. sapiens are much bigger/have
many more base pairs than bacteria
X can have A, B, AB and O as possible phenotypes
Describe ABO blood groups as an example of codominance.
Allele IA and the allele IB are (co)dominant as they are both expressed in the
heterozygote/AB type blood
Sickle-cell anemia affects the ability of red blood cells to transport
oxygen.Explain the consequence of the mutation causing sickle-cell anemia in
relation to the processes of transcription and translation.
caused by single base substitution (mutation);
mutation in gene coding for (one of) polypeptide chain in hemoglobin/HbA;
GAG (on sense strand of DNA) mutated to GTG;
when transcribed, RNA sequence/codon becomes GUG rather than GAG;
during translation, have one amino acid substituted for another;
causes glutamic acid/glutamate to be replaced by valine;
change alters folding of Hb protein/makes RBCs sickle-shaped (in low oxygen);
sickle shaped cells block capillaries/cause tissue damage and pain;
caused by gene mutation;
(sickle-cell anemia) due to a base substitution (mutation);
changes the code on the DNA;
which leads to a change in transcription / change in mRNA;
DNA changes from CTC to CAC/GAG to GTG / mRNA changes from GAG to
GUG; (accept DNA changes from CTT to CAT/GAA to GTA / mRNA changes from
GAA to GUA)
which (in turn) leads to a change in translation / change in polypeptide chain/
protein;
(the tRNA) adds the wrong amino acid to the polypeptide chain;
glutamic acid replaced by valine;
produces abnormal hemoglobin;
causing abnormal red blood cell/erythrocyte shape / sickle shape;
which lowers the ability to transport oxygen;
sickle-cell allele is codominant;
homozygote/HbS HbS have sickle cell anemia/is lethal / heterozygote/HbS HbA
has the sickle trait/is carrier (and is more resistant to malaria);
Describe the causes of Down syndrome.
Down syndrome is caused by non-disjunction;
occurs during meiosis;
chromosome pairs fail to separate in meiosis I / chromatids in meiosis II / anaphase
II;
some gametes have an extra chromosome; 2 chromosomes
can lead to zygotes/individuals with an extra chromosome / individual has 47
chromosomes;
in Down syndrome this would be trisomy 21/extra chromosome 21;
increased probability with increased age of mother/ages of parents;
non-disjunction;
chromosomes/chromatids do not separate / go to same pole;
non-separation of (homologous) chromosomes during anaphase I;
due to incorrect spindle attachment;
non-separation of chromatids during anaphase II;
due to centromeres not dividing;
occurs during gamete/sperm/egg formation;
less common in sperm than egg formation / function of parents' age;
Down syndrome due to extra chromosome 21;
sperm/egg/gamete receives two chromosomes of same type;
zygote/offspring with three chromosomes of same type / trisomy / total 47
chromosomes;
Non-disjunction in another case could mean a missing chromosome too
Describe how human skin colour is determined genetically.
skin colour is an example of polygenic inheritance; continuous variation
many/more than two genes contribute to a person’s skin colour;
due to the amount of melanin in the skin;
combination of alleles determines the phenotype;
no alleles are dominant / alleles are co-dominant / incomplete dominance;
allows for range of skin colours / continuous variation of skin colour;
phenotypes do not follow simple Mendelian ratios of dominance and recessiveness;
the environment also affects gene expression of skin colour / sunlight/UV light
stimulate melanin production;
the more recessive alleles there are, the lighter the skin colour; (vice versa)
skin colour controlled by cumulative effect/combination of genes/alleles;
Explain the consequences of altering a DNA base in the genome of an organism.
altering a base (in DNA) is a (point) mutation;
only has an effect if base is in a gene;
when mRNA is produced by transcription one mRNA base is different;
one codon in mRNA is different;
one amino acid is different in the polypeptide;
polypeptide produced by translation of mRNA;
some base changes do not change the amino acid coded for;
structure of polypeptide /protein may be altered;
usually the polypeptide/protein does not function as well;
example given:
disease: sickle cell anemia;
mutation: GAG to GTG;
consequence in translation: glutamic acid to valine;
consequence for protein: hemoglobin altered so sickle cell formed;
consequence for individual: less oxygen can be carried;
Define the term allele as used in genetics.
allele: one specific form of a gene (occupying the same gene locus as other alleles
of the same gene)
List the possible genotypes for blood group B.
IBIB and IBi
State one type of environmental factor that may increase the mutation rate of a
gene.
a. radiation
b. chemical mutagens/carcinogens/papilloma virus/cigarette smoke
Identify one type of gene mutation.
Base substitution/insertion/deletion/frameshift
Discuss the role of genes and chromosomes in determining individual and
shared character features of the members of a species.
Genes
a. mutation changes genes/causes genetic differences
b. genes can have more than one allele/multiple alleles
alleles are different forms/versions of a gene
c. different alleles «of a gene» give different characters
variation in alleles between individuals
d. eye colour/other example of «alleles of» a gene affecting a character
e. alleles may be dominant or recessive
dominant alleles determine trait even if recessive allele is present
f. both alleles influence the characteristic with codominance
reference to polygenic inheritance
g. all members of a species are genetically similar/have shared genes
certain genes expressed in all members of a species
h. reference to epigenetics/methylation/acetylation / not all genes are expressed «in
an individual»
i. genes are inherited from parents/passed on to offspring/passed from generation to
generation
Chromosomes
j. same locus/same position of genes
same sequence of genes/same genes on each chromosome «in a species»
k. same number of chromosomes «in a species»/all humans have 46
chromosomes/differences in chromosome number between species
l. some individuals have an extra chromosome/Down syndrome/other example of
aneuploidy
polyploidy divides a species/creates a new species
m. X and Y/sex chromosomes determine the sex/gender of an individual
n. meiosis/independent assortment/fertilization/sexual reproduction give new
combinations «of chromosomes/genes»
Outline the process of speciation.
a. speciation is the splitting of a species «into two species»
b. reproductive isolation/lack of interbreeding
c. isolation due to geography/«reproductive» behavior/«reproductive» timing
d. polyploidy can cause isolation
e. gene pools separated
f. differences in/disruptive selection cause traits/gene pools to change/diverge
g. gradualism / speciation/changes accumulating over long periods
h. punctuated equilibrium / speciation/changes over a short time period
Discuss evolution by gradualism and punctuated equilibrium.
a. both describe the pace/speed/rate of evolution;
b. gradualism suggests that evolution occurs over a long time;
c. gradualism changes are slow/steady over time;
d. gradualism would occur when there is little change in the environment;
e. punctuated equilibrium implies long periods with no change;
f. punctuated equilibrium implies short periods with great change;
g. punctuated equilibrium occurs when there are great changes in the environment;
h. example; (eg: in times of volcanic activity/meteorite impact/great climate
change / OWTTE)
i. generally accepted that both ideas take place in evolution
Explain how a base substitution mutation, such as GAG to GTG, can lead to a
disease like sickle-cell anemia.
change in the codon (of the mRNA);
tRNA with a different anticodon attaches;
(if codon changed) wrong/different amino acid is joined to peptide/glutamic acid
replaced by valine;
distorted hemoglobin molecule alters red blood cell shape/reduces ability to carry
oxygen;
Outline a technique of gene transfer resulting in genetically modified organisms.
gene transfer takes a gene from one species/organism and inserts it into another;
mRNA/gene coding for the factor extracted from the cell or tissue
using plasmid/viral vector/ballistic impregnation/electroporation;
use of reverse transcriptase to obtain gene from mRNA; copied to DNA
restriction enzyme/endonuclease used to cut out/excise gene;
(same) restriction enzyme used to cut open plasmid;
sticky ends used to link DNA/link gene to plasmid;
DNA ligase used to seal nicks/splice;
seals sugar-phosphate bonds
recombinant plasmid/plasmid containing desired gene taken up by bacteria;
h. isolate/clone the recombinant/transformed bacteria;
i. bacteria cultured/grown in fermenter to produce factor IX;
bacterium takes in plasmid / plasmid transferred to bacterium/plant/host cell;
valid documented example (e.g. human insulin from bacterium/yeast / salt-tolerant
tomato plant / carotene/vitamin A in rice /
herbicide/Roundup/glyphosate resistance in crop plants / factor IX/clotting factor
in sheep milk / low phosphate feces in pigs;
Explain the use of karyotyping in human genetics.
Definition and construction of karyotypes:
karyotype is the number and type / image of chromosomes in a cell;
cells collected from chorionic villus / by amniocentesis;
requires cells in metaphase / stimulate cells to divide and reach metaphase;
burst cells and spread chromosomes / photo taken of chromosomes;
chromosomes are arranged in pairs;
according to size/structure/position of centromere/banding pattern;
Uses for karyotypes:
karyotypes used to identify sex/gender;
male is XY and female XX;
used to identify chromosome mutations/abnormal numbers/non-disjunction;
Down syndrome due to extra chromosome 21 / other trisomy/aneuploidy example;
used for pre-natal diagnosis of chromosome abnormalities;
may lead to a decision to abort the fetus;
prepare for consequences of abnormality in offspring;
Outline the inheritance of a named sex-linked condition in humans.
genes that are located on just one of the sex chromosomes/X or Y are sex-linked;
(sex-linked) genes present on the X chromosome are absent from the Y
chromosome / vice versa;
named recessive X-linked condition (e.g. colour blindness / haemophilia / other
valid example);
sex-linked conditions tend to be more commonly expressed in males;
female can be homozygous or heterozygous/carrier for a sex-linked/X-linked
condition;
affected males have only one copy of the gene / have carrier daughters but cannot
pass the condition on to sons;
carrier/heterozygous females can have affected sons/carrier daughters;
for a female to be affected (homozygous recessive) the father must be affected;
Explain the inheritance of colour blindness.
a. colour blindness caused by recessive allele / colour blindness is recessive;
b. gene located on X chromosome/sex-linked;
c. Xb is allele for colour blindness and XB is allele for normal colour
vision/dominant allele;
d. male has one X and one Y chromosome;
e. male has only one copy of gene(s) located on X chromosome;
f. X chromosome (in males) comes from female parent;
g. any male receiving allele from mother will express the trait;
h. XbY is genotype for colour blind male;
i. many more males have colour blindness than females;
j. female will express colour blindness only if is homozygous recessive/Xb Xb;
k. heterozygous/XB Xb female is a carrier;
l. colour blind female could be born to colour blind father and carrier mother;
Describe the role of sex chromosomes in the control of gender and inheritance of
hemophilia.
two sex chromosomes are X and Y;
one sex chromosome inherited from each parent;
XX results in female;
XY results in male;
sex determined by sperm/father;
sex-linked genes are those located on the sex chromosomes / usually refers to
genes on X chromosome;
Y chromosomes do not have the allele
recessive sex-linked traits appear more frequently in males since they only have
one X chromosome;
hemophilia is an example of a gene located on the X chromosome/sex-linked;
female carriers are heterozygous / XHXh;
males with hemophilia are XhY / normal males are XHY;
sons (of carrier females) have 50 % probability of showing the trait (even if father
is normal);
daughters (XhXh) of hemophiliac father and carrier mother can be affected /
daughters who receive an affected X from each parent will have hemophilia;
males inherit their X chromosome from their mother/do not pass the allele to sons;
affected/hemophiliac males have carrier daughters;
hemophilia allele could have been inherited from either parent;
Define the terms chromosome, gene, allele and genome.
chromosome: structure formed by DNA and proteins;
gene: a heritable factor that controls a specific characteristic;
allele: one specific form of a gene occupying the same gene locus as other alleles
of the gene;
genome: the whole of the genetic information of an organism;
A mule was born at the University of Idaho in the USA with 64 chromosomes.
Suggest a mechanism by which this could happen.
Non-disjunction
Distinguish between autosomes and sex chromosomes in humans.
X and Y chromosomes determine sex;
females XX and males XY;
X chromosome is larger than / carries more genes than the Y chromosome;
22 types/pairs of autosomes;
males and females have same types of autosomes;
Explain how meiosis results in an effectively infinite genetic variety of gametes.
one (homologous) chromosome is from the mother and one from the father;
homologous chromosomes pair (in prophase I);
crossing over/chiasma formation in prophase I;
recombination of linked genes / alleles/genes swapped;
many possible points of crossing over;
crossing over occurs at random positions;
due to crossing over the two chromatids of metaphase I chromosomes are not
identical;
random orientation (of bivalents) in metaphase I;
in anaphase/at end of metaphase I chromosomes move to opposite poles;
independent assortment of chromosomes/genes;
2n/223 combinations (without considering crossing over);
four genetically different nuclei/gametes from each meiosis;
Deduce with reasons for your answer, whether the chromosomes are autosomes
or sex chromosomes.
autosomes because the sex chromosomes/X and Y chromosomes would be
different lengths/sizes / would have different genes
Deduce with reasons for your answer, whether the chromosomes are
homologous or non-homologous.
homologous because they have paired/formed a bivalent / tetrad / there is crossing
over between the chromosomes / they have the same genes (in the same sequence)
/ they are the same size and shape.
State the stage of meiosis of a cell if it contains pairs of chromosomes as shown
in the diagram.
first prophase/first metaphase/prophase I/metaphase I
Determine the combinations of alleles that would be present on each chromatid.
Use the diagrams to indicate your answer.
State the pattern of inheritance shown by the three genes.
(gene) linkage / autosomal linkage
State the technique used to collect cells for pre-natal testing.
amniocentesis/sampling amniotic liquid/fluid (via needle)/chorionic villus
sampling
State the method used to arrange the chromosomes in a karyotype.
chromosomes are grouped by pairs according to size and structure/band
pattern/location of centromeres
State at what stage in the cell cycle the cells would be when this photograph was
taken.
metaphase/late prophase of mitosis
Explain how sexual reproduction can lead to variation in a species.
allows characteristics from both parents to appear in offspring;
crossing over (during prophase 1) changes chromosome composition;
produces gametes which are all different;
random chance of which sperm fertilizes ovum;
greater variation (resulting from sexual reproduction) favours survival of species
through natural selection;
Following fertilization, cells in the developing embryo differentiate. Outline a
technique for cloning using differentiated animal cells.
a. differentiated/somatic/diploid cells taken from donor animal/sheep udder;
b. (diploid) nucleus from donor cells removed;
c. ova/eggs cells removed from (donor) animal/female sheep;
d. (haploid) nucleus removed from eggs/ova;
e. (diploid/donor’s) nucleus is fused with/inserted into egg/ovum (to form zygote);
f. embryo (from cell with donor nucleus and egg from surrogate) implanted in
uterus of surrogate mother;
g. normal pregnancy and birth is completed;
h. offspring is a genetic copy/clone of the donor mother/diploid nucleus
Discuss ethical issues of therapeutic cloning in humans.
a. therapeutic cloning involves producing embryos from which embryonic stem
cells can be harvested for medical use;
argument in favour:
b. (to many people) any procedure that reduces pain and suffering is
ethically/morally justified;
c. stem cells can be used to replace organs/tissues that have been lost/damaged in a
patient;
d. (thus) pain and suffering can be reduced/lives can be saved/life quality
improved;
e. cells can be removed from embryos that have stopped developing and would
have died anyway;
f. cells are removed at a stage when no pain can be felt by the embryo;
g. use embryos from IVF that would otherwise be destroyed;
argument against:
h. embryonic stem cells are no longer needed as adult stem cells can be used
without causing loss of life;
i. there is danger of embryonic stem cells developing into tumour cells/harmful
effects are not yet known;
j. every human embryo is a potential human with the right to development;
k. more embryos may be produced than can be used and so some would be killed;
l. (to many people) any procedure that harms a life/kills is unethical/morally
wrong;
Linked Genes
Codominant
Allele
Genes located on the same chromosomes
Pair of alleles that both affect the phenotype when present
in a heterozygote / both alleles are expressed;
Recessive Allele
An allele that produces its characteristic phenotype only
when present in homozygous state / is expressed when
dominant allele not present;
Locus
The (particular) position of a gene on a
chromosome/homologous chromosomes;
Sex-linkage
A gene located on a sex chromosome/ X or Y
chromosome;
Linkage Group
Genes that are located on the same chromosome form a
linkage group
Gene Pool
All of the genes/alleles in an interbreeding population
Using an example, describe polygenic inheritance.
more than one gene contribute to/control same characteristic;
as number of genes increase so does possible number of phenotypes;
leads to continuous variation;
specific example; (eg human skin color (due to differing amounts of melanin))
human skin colour can vary from pale to very dark / amount of melanin varies;
skin colour/melanin controlled by (alleles from) at least three/several genes;
no alleles are dominant / alleles are co-dominant / incomplete dominance;
many different possible combinations of alleles;
skin colour controlled by cumulative effect/combination of genes/alleles;
I – Bacterial Cell
II – Plasmid
III – Desired gene from donor cell
IV – Host cell with a recombinant plasmid
Gel electrophoresis
Male 1 is the father as all bands/alleles match either mother or Male 1
Using a named example of a genetically modified crop, discuss the specific
ethical issues of its use.
a. named example of verified genetically modified crop; eg, Bt corn / golden rice;
b. specific gene added / new protein synthesized by the crop plant / specific
modification; eg gene from Bacillus thuringiensis / cry protein;
c. biological effect of the modification; eg, makes the plant toxic to (herbivorous)
insects / insect pests / corn borers;
d. a benefit of specific genetic modification; eg, increased crop yields / less land
needed;
e. a second benefit of this specific modification; eg, reduced need for use of
chemical pesticides;
f. a harmful effect of specific genetic modification; ingestion of toxin by nontarget
species;
g. another specific harmful effect; eg, concerns about contamination of
neighbouring non-GMO crops affecting trade;
Outline natural methods of cloning in some eukaryotes.
a. clones are genetically identical organisms
group of cells derived from a single parent cell
b. asexual reproduction in plants such as tubers/runners/bulbs
Allow other verifiable examples of plants
c. common in non-vertebrates such as budding in hydra
d. budding in yeast/fungi
e. identical twins «in humans» are clones because they originate from
the same cell
State an application of plasmids in biotechnology.
transfer/vector of genetic material/genes/DNA fragments or
to produce insulin/useful protein
Explain benefits and risks of using genetically modified crops for the
environment and also for human health.
Environment benefits:
a. pest-resistant crops can be made
b. so less spraying of insecticides/pesticides
c. less fuel burned in management of crops
d. longer shelf-life for fruits and vegetables so less spoilage
e. greater quantity/shorter growing time/less land needed
f. increase variety of growing locations / can grow in threatened conditions
allows crops to be grown where they would not grow naturally;
provides more food;
economic benefits;
expands world’s productive farmland;
reduces the need to clear rainforests to grow crops;
lowers cost of production;
less pesticides/fertilizers/chemicals needed so better for environment;
Environment risks:
g. non-target organisms can be affected
h. genes transferred to crop plants to make them herbicide resistant could spread to
wild plants making super-weeds
i. GMOs (encourage monoculture which) reduces biodiversity
j. GM crops encourage overuse of herbicides
may be released into natural environment;
may affect food chains / unintended effects on other organisms;
may affect consumers e.g. allergies/health risks;
unfair to smaller farmers who cannot compete;
long-term effects are unknown; risk of cross-pollination;
risk of long-term contamination of soil;
Health benefits:
k. nutritional value of food improved by increasing nutrient content
l. crops could be produced that lack toxins or allergens
m. crops could be produced to contain edible vaccines to provide natural disease
resistance
Health risks:
n. proteins from transferred genes could be toxic or cause allergic reactions
o. antibiotic resistance genes used as markers during gene transfer could spread to
«pathogenic» bacteria
p. transferred genes could cause unexpected/not anticipated problems
health effects of exposure to GMO unclear
Discuss the benefits and possible harmful effects of altering species by one
example of genetic modification.
DNA is universal (genes can be transferred among species);
gene modification is the transfer of genetic material between species;
named example; (e.g. glyphosate resistant crops)
source of gene; (e.g. bacteria)
function of gene; (e.g. resistance to herbicides)
modified organisms; (e.g. soya beans)
argument in favour/benefit of named example; (e.g. increase in crop yield)
argument in favour/benefit of named example; (e.g. reduction in use of herbicides)
argument in favour/benefit of named example; (e.g. glyphosate breaks down into
naturally occurring components so glyphosate resistant crops are justified)
argument against/risk of named example; (e.g. (application of) glyphosate could
cause cancer in future)
argument against/risk of named example; (e.g. could be transferred to wild plants)
argument against/risk of named example; (e.g. genetically modified crops may
cause allergies)
Describe karyotyping and one application of its use.
cells undergoing mitosis are used for karyotyping;
process of mitosis is stopped at (mitotic) metaphase;
chromosomes (cut from photographs) are arranged in pairs of similar structure/
homologous chromosomes;
allows abnormalities in the chromosome number/appearance to be seen;
any valid example (e.g. in Down syndrome / gender of fetus);
detected by identifying unique feature (e.g. trisomy 21 / one extra chromosome /
47 chromosomes);
Describe the process of crossing over.
a. occurs during prophase I/during meiosis
b. homologous chromosomes form bivalents/pair up
c. breakage and rejoining of chromatids
d. exchange «of DNA/alleles» between non-sister chromatids/homologous
chromosomes
Explain the reason for linked genes not following the pattern of inheritance
discovered by Mendel.
a. «linked genes are» on the same chromosome
b. Mendel's genes were on different chromosomes
c. linked genes are inherited together
no independent assortment
d. «linked genes» only separated by crossing over
fewer recombinants than with unlinked genes
Outline the formation of chiasmata during crossing over.
crossing over/chiasmata formed during prophase I of meiosis;
pairing of homologous chromosomes/synapsis;
chromatids break (at same point); (do not accept chromatids overlap)
non-sister chromatids join up/swap/exchange alleles/parts;
X-shaped structure formed / chiasmata are X-shaped structures;
chiasma formed at position where crossing over occurred;
chiasmata become visible when homologous chromosomes unpair;
chiasma holds homologous chromosomes together (until anaphase);
called recombinants
Explain how meiosis promotes variation.
a. (in prophase I) crossing over/chiasmata formation (between homologous
chromosomes);
b. random alignment of homologues/bivalents in metaphase I / independent
assortment of homologues / chromosomes;
random orientation of chromatids/chromosomes in metaphase 2;
c. second division of meiosis separates alleles further;
d. combinations of alleles in gametes is unlimited/2n;
Compare the information that could be deduced when the genotypes are
presented as AaBb or
Outline how reproductive isolation can occur in an animal population. OR
Starting from the concept of gene pool, explain briefly how populations of early
vertebrates could have evolved into different groups.
a. can be sympatric or allopatric
b. temporal isolation by members of difference populations reproducing at different
times OWTTE
c. behavioural isolation by difference in courtship behaviours OWTTE
d. geographic isolation by a population being separated by river/mountain/barrier
to contact
An example of a geographic barrier is required.
e. polyploidy
Outline what is required for speciation to occur.
a. divided species/gene pool / part of species/gene pool becomes separated /
species splits into separate populations
b. reproductive isolation8= / lack of interbreeding
Mark point b refers to a lack of interbreeding between separated populations in a
species, not the lack of interbreeding after speciation.
c. may be due temporal/behavioural/geographic isolation
d. different natural selection/different selective pressures
List two causes of variation within a gene pool.
a. sexual reproduction / random fertilization / meiosis
b. mutation
Describe one type of barrier that may exist between gene pools.
named barrier;
description of its action;
results in terms of gene pools;
e.g.:
behavioural barrier;
different populations mate at different times of year thus preventing interbreeding;
allele frequencies become different in the two gene pools/separates gene pools /
sympatric speciation;
Explain how polyploidy can contribute to speciation.
Polyploidy:
a. having more than 2 (complete) chromosome sets/description of polyploidy;
b. happens through chromosome mutation / non-disjunction;
c. occurs more frequently in plants than animals;
Contribution to speciation
d. polyploids cannot reproduce with original species / meiosis fails / chromosomes
cannot pair;
e. creates reproductive barrier;
f. but can self-fertilize / reproduce with similar individuals;
g. thus forming a new species;
h. new species formed by sympatric speciation;
Compare sympatric speciation and allopatric speciation.
both involve reproductive isolation / separation of gene pools;
sympatric is speciation due to isolation of populations living in the same
geographic area whereas allopatric is speciation due to geographic isolation;
Compare convergent and divergent evolution.
Discuss the concept of punctuated equilibrium.
long periods of stability;
environmental change / sudden change;
leads to rapid speciation/evolution;
helps to explain absence of intermediate forms;
competing theory is gradualism;
State the name given to the situation where two alleles of a gene persist
indefinitely in a population.
Balanced polymorphism
The total frequency of both alleles will be 100% – in other words: p + q = 1
• Because genotypes consist of two alleles, this equation must be squared: ( p +
q)2 = 1
• This gives the expanded Hardy-Weinberg equation: p2 + 2pq + q2 = 1
Suppose we had a population of 500 people, in which 9% were albino (albinism
is a recessive characteristic)
How many individuals in this population are heterozygous?
Using the equations: p + q = 1 and p2 + 2pq + q2 = 1
§
If q2 = 0.09 ⇒ q = 0.3 (√ 0.09)
§
If q = 0.3 ⇒ p = 0.7 (p + 0.3 = 1)
§
If p = 0.7 ⇒ p2 = 0.49 (0.72)
§
2pq = 0.42 ⇒ (0.49 + 2pq + 0.09 = 1)
Substituting these numbers for frequencies and applying them to the original
population shows that:
§
49% of people are homozygous dominant (AA), which is 245 individuals
(0.49 × 500)
§
9% of people are homozygous recessive (aa), which is 45 individuals (0.09
× 500)
§
42% of people are heterozygous (Aa), which is 210 individuals (0.42 ×
500)
Chapter 4, 5
Define saprotrophic organisms.
An organism that secretes enzymes in dead organic matter and absorbs its nutrients/products of
digestion. It survives on dead organic matter. Examples are bacteria and fungi.
State one role of saprotrophic organisms in the ecosystem.
Decomposer / recycle nutrients / break down organic material into inorganic material
Distinguish between autotrophs and heterotrophs.
autotrophs make their own food/organic molecules/organic matter and heterotrophs feed
on/obtain their food/organic molecules from other organisms;
autotrophs use/require inorganic molecules/CO2 and heterotrophs require (complex) organic
molecules;
Define the terms species, population and community.
species: group of organisms that can interbreed to produce fertile offspring;
population: group of organisms of the same species living in the same area at the same time;
community: group of populations living and interacting with each other in an area;
habitat: the environment in which a species normally lives / the location of a living organism
ecosystem: a community and its abiotic environment
Explain the shape of the pyramids of energy that are constructed by ecologists to represent
energy flow in an ecosystem.
energy flows up from one trophic level to the next (in a community);
energy is lost at each stage by waste products/feces/not all the organism is consumed;
most energy is lost through respiration/heat;
each level on the pyramid is about 10% – 20% of the size of the one below it / 80% – 90%
energy lost between levels;
labelled diagram of pyramid of energy (indicating trophic levels);
Suggest one advantage and one disadvantage for blood sampling rather than weighing birds to
assess food quality at stopover sites.
Advantage:
need to capture bird only once to get data / no need to mark and catch birds again;
more informative data can be gathered; (do not accept unqualified “more precise”)
Disadvantage:
removal of blood is more stressful/risky for the bird than weighing;
danger of infection / spread of disease / harm to birds;
extra time/money/laboratory equipment is needed to analyse results;
could include fat/triglyceride/butyrate from previous/long-term feeding;
nutrients from food eaten at these sites may not have been absorbed yet;
Outline how energy flows through an ecosystem.
producers/plants/autotrophs convert light energy into chemical energy/make food by
photosynthesis;
such as sugars/organic compounds;
producers eaten by primary consumers, these by secondary consumers, (these by tertiary
consumers)/energy moves up trophic levels;
only a small percentage/10–20 % of the energy is passed along food chain;
energy lost in the form of heat;
energy lost by (cell) respiration;
energy lost as not digested/lost in feces;
energy lost through death of organisms;
passed to detritivores/saprophytes/decomposers;
energy is not recycled;
Discuss whether or not horses and donkeys should be placed in the same species.
a. to be in same species two organisms must have the same genes arranged on the same
chromosomes or must have the same number of chromosomes
b. members of same species produce fertile offspring and a mule is not fertile
Discuss the need for international cooperation to solve the problems of declining coral
populations.
a. international cooperation needed to reduce carbon dioxide emission/concentrations
b. carbon dioxide produced anywhere increases the greenhouse effect/global warming/ocean
acidification/health of coral everywhere
c. ocean currents/tides/wind move carbon dioxide/acid/heat around the world / oceans of the
world are interconnected/part of one overall system
d. (some) coral reefs are in international waters (or words to that effect) / coral reefs cannot be
protected by single national governments alone
e. the more groups of people/nations/corporations that reduce their carbon emissions, the lower
the impact on coral will become / not enough for one country/group/corporation to reduce carbon
dioxide emissions
f. sharing of technology/research/information/resources
g. aid to poorer/developing countries (to help with coral conservation)
h. reference to an economic/ecological benefit of conserving coral reefs
Most of the surface of the Earth is covered with a wide diversity of ecosystems. Outline two
general characteristics of all ecosystems.
a. organisms/community plus the environment / biotic and abiotic «components»
b. interactions
c. ecosystems show sustainability
d. nutrients are recycled in ecosystems
e. energy flows through ecosystems
f. producers «are part of all ecosystems»
Detritivores ingest non-living organic material, eg. earthworms and woodlice
Outline the energy flow through this food web.
a. light energy of Sun is converted by plant/autotroph to chemical energy «in carbon compounds
through photosynthesis»
b. detritivores/saprotrophs decay plant material «that accumulates in the soil» to obtain energy
c. consumers release energy from the carbon compounds by cell respiration energy lost as heat
d. energy is used by organisms for metabolism
e. energy is transferred between organisms/trophic levels through the food chains/web
For mp e, accept specific example such as energy is transferred from primary to secondary
consumer etc.
f. energy is lost at each trophic level «so lengths of food chains/web are restricted»
approximately 80/90 % of energy is lost «between trophic levels»
Explain the flow of energy between trophic levels in ecosystems.
sunlight is the initial source of energy for (most) ecosystems;
sunlight (energy) is converted (through photosynthesis) into chemical/potential energy by
producers/plants/autotrophs;
producing C6H12O6 /sugars/carbohydrates
carbon/organic compounds used for energy/growth/repair/storage
energy escapes from an ecosystem (as heat) / is not recycled;
flow of energy through an ecosystem can be represented as a pyramid of energy; (allow a
suitable diagram)
energy flow in an ecosystem is measured as energy per unit area/volume, per unit time, for
example kJ m–2 yr–1/ kJ m–3 day–1 / other valid unit;
(chemical) energy is passed along the food chain/trophic levels;
primary consumer/herbivores obtain energy from plant food;
secondary/tertiary consumer/carnivores obtain energy by eating other (animals);
energy transfer between trophic levels is not 100 % efficient / is only about 10% efficient;
some energy is lost as heat through respiration;
ATP produced
energy/ATP used for biosynthesis/movement/active transport/other valid use of ATP
energy lost in bones/hair when they die/not fully eaten by the next trophic level
energy lost in feces/urine
decomposers obtain energy from waste products/dead bodies/leaf litter;
energy is not recycled
Ecologists sometimes display data from an ecosystem using a diagram called a pyramid of
energy. Describe what is shown in pyramids of energy.
a. pyramid of energy shows the flow of energy from one trophic level to the next (in a
community);
b. units of pyramids of energy are energy per unit area per unit time/kJ m–2 yr –1;
c. bar width is proportional to the energy stored (in the biomass) in that trophic level;
d. the first/lowest trophic level is producers;
e. second level is primary consumers/herbivores;
f. third level of secondary consumers/carnivores;
g. only a small amount (10 to 20 %) of energy of one level is passed to the next;
h. bar width/energy stored in the trophic level decreases (proportionally) as you go up each level;
i. pyramid shows that there is a limit to the length of food chains;
more energy available if feeding at an earlier stage in a food chain
Distinguish between the movement of energy and nutrients in an ecosystem.
energy moves through/enters and leaves ecosystems / need a constant source of energy;
energy is not recycled
nutrients are recycled by saprotrophs/returned to environment and reused;
while energy (enters as light and) is dispersed as heat;
nutrients cycled between biotic and abiotic environment/in cycles such as C/N;
Describe the movement of energy and nutrients in an ecosystem.
ecosystem is a community and its abiotic environment;
solar energy collected by autotrophs/plants (via photosynthesis);
moves through trophic levels via food;
only 5 to 20% transferred from one trophic level to next / never 100% efficient;
lost as metabolic heat/organic waste;
energy flow can be illustrated by pyramid shape;
organisms absorb nutrients from food/environment;
nutrients occur as complex organic matter in living organisms;
after death, saprotrophic bacteria and fungi (decomposers) breakdown complex organic matter;
breakdown products are simpler substances;
absorbed into plants for resynthesis into complex organic matter/recycled;
Describe what is meant by a food chain and a food web.
a. food chain shows transfer of nutrients/energy in an ecosystem / arrows from one trophic level
to the next in examples;
b. between different trophic levels / shown in a correct chain or web;
c. starting with a producer;
d. followed by at least two levels of consumers / shown in a correct chain or web;
e. food web is the (branched) interaction of multiple food chains / cross arrows in examples;
f. using (multiple) producers as a source;
g. transferring nutrients/energy to consumers from different food chains;
h. same consumer could be at different trophic levels in a food web;
a. food chain shows feeding/trophic relationships;
b. showing which organism/animal eats which organism;
c. showing the flow of energy from producer/autotroph to top consumer/top carnivore / through
trophic levels;
Explain the relationship between rises in concentration of atmospheric gases and the
enhanced greenhouse effect.
a. water vapour;
b. carbon dioxide;
c. methane;
d. oxides of nitrogen;
e. all (of these gases) occur naturally;
f. and human activity has increased the normal level of these gases in recent years;
g. incoming shorter wave radiation from the Sun;
h. is re-radiated as longer wave radiation/infrared;
i. (mainly) in the form of heat;
j. captured by greenhouse gases;
k. which increases the atmospheric/ocean temperature;
l. at a higher rate than normal / creating a positive imbalance;
m. which threatens ecosystems/climatic patterns/ocean patterns;
n. Earth’s history had many fluctuations in gas levels/global temperature / some scientists are
skeptical about enhanced greenhouse effect;
global warming happened during same time/period as CO2 rise;
CO2 concentration correlated (positively) with global temperature / global temperature increases
as CO2 concentration increases;
(causal) link accepted by most scientists;
no proof that man-made increases in CO2 have caused global warming;
State one reason that the population of mountain lions is smaller than the populations of other
animals in the food web.
Mountain lions/highest trophic level receives less energy as energy is lost at each level /
Mountain lions are larger than other animals and require more (smaller) individuals for food.
Explain the role of decomposers in an ecosystem.
a. saprotrophs/decomposers feed on/break down dead «organic» matter
b. saprotrophs/decomposers release energy «heat» accelerating decomposition/warming soil
c. saprotrophs/decomposers recycle nutrients / make nutrients available (to producers)
OR
improves soil fertility / returns nutrients (minerals/nitrates/phosphates/carbon)to
soil/water/environment
d. saprotrophs/decomposers detoxify waste
Discuss the processes in the carbon cycle that affect concentrations of carbon dioxide and
methane in the atmosphere and the consequences for climate change.
a. CO2 is produced from respiration in organisms/combustion of biomass/fossil fuels
b. CH4 is produced by anaerobic respiration of biomass/«methanogenic» bacteria
c. CH4 is oxidized to CO2 and water
d. CO2 is converted into carbohydrates/organic compounds by
autotrophs/producers/photosynthesis
e. CO2 can be converted to calcium carbonate/fossilized into limestone
f. «partially» decomposed organic matter/biomass can be converted into peat/coal/oil/gas/fossil
fuels
g. CO2 and CH4 are both greenhouse gases/increase greenhouse effect
h. both absorb long-wave radiation from the earth and retain the heat in the atmosphere
i. increased CO2 concentrations in the atmosphere correlate with increased combustion of fossil
fuels
j. rising average global temperatures correlate with more greenhouse gases in the atmosphere
k. cattle production/rice paddy/defrosting of tundra increase CH4 in the atmosphere
OR
increasing CO2 leads to acidification of marine/aquatic environments
l. the global temperature increase influences/disrupts climate patterns
Outline the precautionary principle.
some human-induced change can be very large/perhaps catastrophic;
those responsible for the change must prove it will cause no harm before proceeding;
appropriate (environmental/medical etc.) example e.g. companies must immediately reduce
emission of greenhouse gases even though proof of human impact on global warming is still
debated;
is reverse of historical practice / previously those concerned about change had to prove it will do
harm to prevent such changes from going ahead / paradigm shift;
objectors do not have to prove that there will be harm;
activities that risk/threaten/may cause harm are banned;
trials/tests must be done first;
precautionary principle is applied when possible consequences are severe;
precautionary principle should be used in the case of global warming;
action should be taken to reduce CO2 emissions before proved it is the cause;
another example of implementation of the precautionary principle;
Explain how the emission of gases, both naturally and through human activity, can alter the
surface temperature of the Earth.
increase in temperature is called global warming;
this is caused by the greenhouse effect;
a natural phenomenon that has occurred over millions of years;
main gas responsible is carbon dioxide;
other gases like methane/nitrous oxide also cause effect;
shortwave radiation from the Sun enters atmosphere;
warms the surface of the Earth;
longwave radiation emitted by the surface of the Earth;
is absorbed by carbon dioxide/greenhouse gases;
human use of fossil fuels has increased levels of atmospheric carbon dioxide;
rapid rise in temperatures over (approximately) hundred years;
cows/animals/peat bogs release methane;
greenhouse gases emitted by volcanic activity;
Outline the causes and consequences of the enhanced greenhouse effect.
burning of (fossil) fuels/coal/oil/gas releases carbon dioxide;
deforestation/loss of ecosystems reduces carbon dioxide uptake;
methane emitted from cattle/livestock/melting permafrost/waste dumps;
heating of the atmosphere/global warming/climate change;
melting of ice caps/glaciers/permafrost / sea level rise / floods / droughts / changes in ocean
currents / more powerful hurricanes / extreme weather events / other abiotic consequence;
changes in species distributions/migration patterns / increased decomposition rates / increases in
pest/pathogen species / loss of ice habitats / other biotic consequence;
Explain how the process of photosynthesis affects carbon dioxide concentrations in the
atmosphere during a typical year and the likely consequences on Earth of the yearly rises in
carbon dioxide concentrations.
a. photosynthesis uses carbon dioxide;
b. CO2 fixed/made into organic molecules/compounds by photosynthesis;
c. lowering carbon dioxide level in atmosphere;
d. annual/seasonal fluctuations of carbon dioxide levels could be related to photosynthesis;
e. caused by increased photosynthesis during spring/summer;
Consequences:
f. enhanced greenhouse effect caused by raised levels of carbon dioxide;
g. causing global warming;
h. rising of ocean levels / melting of polar ice caps/glaciers;
i. changes in weather (patterns);
j. ocean acidification;
k. alter food webs;
l. changes/loss of habitat;
m. changes in distribution of plants and animals;
n. may lead to extinction;
Describe the process of peat formation.
a. formed from dead plant material/leaves/mosses/Sphagnum
b. formed in waterlogged sites/bogs/mires/swamps
c. where bacteria/fungi/saprotrophs are not active/are inhibited
d. organic matter not fully decomposed
e. «occurs» in acidic conditions
f. «occurs» in anaerobic conditions
g. «very» slow process/takes a long time
Aquatic and other environments are being affected by a global rise in temperature. Outline the
consequences of this on arctic ecosystems.
a. warming results in melting (arctic/polar) ice (cap) / loss of ice habitats;
loss of ice increases absorption of solar radiation increasing warming of atmosphere;
b. (warming) raises sea level / floods coastal areas / destroys coastal habitats;
c. (warming) of habitat would change species/flora/fauna that can be supported (named examples
can be used);
reduced space/habitat (for ice-dwelling species) / valid example;
d. decrease in size of population(s) / possible extinction of species;
e. temperate species move into area / arctic species adapt/move;
changes in water salinity;
increased competition (from temperate species);
f. change in distribution of species/changes in migration patterns;
g. (ecological) changes will affect higher trophic levels/food webs/food chains;
h. increased rates of decomposition of detritus from (melting) permafrost;
i. increased success of pest species including pathogens;
changes in the distribution of prey species affecting higher trohic levels
The enhanced greenhouse effect can cause a rise in atmospheric temperature. Outline one
effect of a temperature rise on plants.
Rate of photosynthesis increases as temperature increases;
rate of transpiration increases as temperature increases;
shift in plant distribution
Outline causes of ocean acidification.
a. carbon dioxide makes an acid/carbonic acid in water
b. (carbon dioxide from) burning fossil fuels/forest fires
c. carbon dioxide forms solution with/dissolves into water/oceans/rain
Suggest causes for the changes in ocean temperature.
a. increased carbon dioxide/methane in the atmosphere / carbon dioxide emissions from burning
of fossil fuels / other specific source of a named greenhouse gas
b. increased greenhouse effect / more heat/long wave radiation trapped in the atmosphere
c. heat transfer from atmosphere to ocean / ocean absorbs heat from atmosphere
The short-tailed albatross (Phoebastria albatrus) nests and breeds on remote low-lying coral
islands in the Pacific Ocean. Predict how global warming may threaten the survival of such
an ocean bird.
a. rising ocean levels/more extreme weather «due to global warming» may destroy
breeding/nesting sites
OR
rising sea level may put island underwater causing young birds/chicks to drown
b. populations may not find/adapt to new colony sites
c. warming seas may affect the food supply
Using the diagram, explain the interaction of short and long wave radiation with greenhouse
gases in the atmosphere.
Short wave radiation/UV «shown as» having its origin in the Sun gives off light as short
radiation
Short wave radiation/UV «shown as» passing through the greenhouse gases «some reflected»
Some short wave radiation/UV is absorbed by the Earth and some is reflected
The reflected radiation is long wave radiation «reflected as heat»
Long wave radiation/IR «shown as» being unable to pass through/being absorbed/reflected by
the greenhouse gases
a. greenhouse gases present (at Z)
b. greenhouse gases «CO2, methane, nitrous oxide, water vapour» absorb
long-wavelengths/infrared
OR
long wavelengths/infrared waves blocked from leaving the atmosphere
c. (long-wavelengths/infrared absorbed and) reradiated/re-emitted (heat Earth)
Define the terms fundamental niche and realized niche.
Fundamental niche:
the potential niche / the niche the organism could occupy under ideal conditions / the full mode
of existence given the adaptations of the species
Realized niche:
the actual niche / the niche restricted by competition and environmental variables / the niche
resulting from the limits placed on the species
Explain why carnivores tend to be more affected by biomagnification than organisms lower
down the food chain.
mercury / DDT / other named example;
biomagnification is the accumulation of chemicals through the food chain;
chemicals that undergo biomagnification are stored/not broken down (in the bodies of the
organisms that consume them);
chemicals are passed (unaltered) from one trophic level to the next;
chemicals become more concentrated in the bodies of each (subsequent) trophic level;
organisms higher up the food chain consume larger amounts of the chemical;
Distinguish between mutualism and parasitism, providing another example of mutualism and
another example of parasitism.
a. in parasitism only one organism benefits whereas in mutualism both benefit
eg parasitic: human tapeworms and mutualism: bacteria in human digestive tract
Distinguish between the exchange of matter and energy with the surroundings in a closed
mesocosm.
Matter does not exchange/enter/leave but energy exchanges/enters/leaves
Suggest one advantage of using a mesocosm in this experiment.
Allows atmospheric CO2 concentration to be controlled/varied
Control other variables
Closed system so no external processes affect experiment
Outline one way in which reef-building corals are affected by increasing atmospheric carbon
dioxide.
Alternative 1
Corals have parts/shells/«exo»skeleton made of calcium carbonate
Calcium carbonate «shells» dissolve in acid conditions
Acid/high CO2 conditions reduces availability of calcium carbonate «for forming shells»
OR
negatively affects enzymes involved in calcification
Alternative 2
CO2 is «significant» greenhouse gas causing rise in ocean temperatures
Higher ocean temperatures/acidification leads to rejection of zooxanthellae
OR
higher ocean temperatures/acidification leads to coral bleaching
Discuss the definition of the term species.
a. meaning of species has changed over time / no longer just based on morphological
features/phenotype;
b. species members also resemble each other in physiology/biochemistry/DNA sequences/use of
habitat/behaviour;
c. but species can evolve and features change/species gradually split up;
d. definition now based on ability to interbreed/produce viable, fertile offspring;
e. gene flow among populations of the species maintains the species’ uniqueness;
f. some interspecific hybrids are fertile making categorization difficult;
g. further accurate discussion point about species definition;
A species is often defined as a group of similar individuals that interbreed in nature and
produce fertile offspring. Discuss some problems with the use of this definition.
a. not all organisms can be defined in this way / does not take into account hybrids/
microorganisms/plants;
b. (even if able to interbreed) may have differences in DNA/protein;
c. does not apply to bacteria/other organisms that reproduce asexually;
d. in sympatric/allopatric isolation members of the same species do not interbreed;
e. (in some species) significant differences in morphology can occur within the same species eg:
sexual dimorphism/metamorphosis/ring species;
Outline the abiotic factors that affect the distribution of plant species in an ecosystem
water (distribution) for turgor/biochemical reactions/photosynthesis;
mineral / inorganic content / salinity of soil/water;
temperature (max, min, range, seasonal changes) / altitude;
light (intensity, duration, wavelength) for photosynthesis;
pH (range, average, changes) of soil/water;
wind (direction, strength);
Mesocosm experiments using water from Narragansett Bay were completed in the laboratory
during a six month period. Discuss advantages and limitations of carrying out mesocosm
investigations.
Advantages of mesocosm experiments:
a. scientist can alter/manipulate/control environmental conditions
b. allows carrying out experiments with many samples / replicates
c. ease of collection of continuous data
Limitations of mesocosm experiments:
d. difficult to mimic natural environmental conditions exactly
e. Natural environments change /are not static
Describe how methane can be made from biomass. Explain the principles involved in the
generation of methane from biomass.
a. anaerobic fermentation of biomass/manure/suitable biomass material;organic
matter/manure/waste/agricultural material/seaweed used;
b. bacteria convert biomass into organic acids and alcohol;
bioreactor with anaerobic conditions; constant temperature / neutral pH in the digester;
bacteria convert organic matter into organic acids/alcohol/acetate/ CO2CO2 and H2H2;
bacteria produce CO2 and H2;
methanogenic bacteria produce methane from breakdown of acetate/ CO2CO2 and H2H2;
e. by reducing/reacting CO2 with hydrogen gas/
State the role of Rhizobium in the nitrogen cycle.
Nitrogen fixation / changes (free) nitrogen to ammonia
Outline the role of saprotrophic bacteria in the treatment of sewage.
sewage trickled over bed of rocks with (biofilm of) saprotrophs and oxygen added;
saprotrophic bacteria feed on/break down organic matter (found in sewage);
transforming it into harmless/re-usable products/ CO2CO2, H2OH2O, ammonia;
Describe the consequences of the potential overproduction of offspring.
a. more (offspring) than the environment can support / carrying capacity reached;
b. increased mortality/lower life expectancy/more deaths;
c. competition (for resources) / struggle for survival;
d. food/mates/nest sites/territory/other example of resource shortage / example of greater need;
e. variation between members of population / example of variation;
f. better adapted more likely to survive / converse; (reject Lamarckian statements such as those
who adapt survive)
g. better adapted reproduce / pass on (favourable) genes/traits / converse;
h. natural selection / (survival of fittest) leads to evolution;
variation/characteristic must be heritable;
best fitted individuals survive to reproduce;
advantageous variation/characteristic/allele passed on;
over time advantageous variation/characteristic/allele increases in the population;
X is the plateau phase
Y is the exponential/log phase
Outline how fossil records can provide evidence for evolution.
a. the sequence in which fossils appear matches the expected sequence of evolution;
b. comparisons with fossils and living organisms (morphology) shows change in characteristics
from an ancestral form / OWTTE;
Vestigial organs and homologous structures are acceptable answers.
c. fossils of extinct species show that (evolutionary) change has occurred;
d. fossils can be dated with radioisotopes / geological depth/strata indicates (relative) age/date of
organism;
e. can yield DNA for molecular clock analysis;
f. example of any of the above can earn one mark (eg: reptiles follow amphibians);
Explain how evolution may happen in response to environmental change with evidence from
examples.
a. variation in population;
b. (variation is) due to mutation/sexual reproduction;
c. valid example of variation in a specific population;
d. more offspring are produced than can survive / populations over-populate;
e. competition / struggle for resources/survival;
f. example of competition/struggle for resources;
g. survival of fittest/best adapted (to the changed environment)/those with beneficial adaptations
/ converse;
h. example of changed environment and adaptation to it;
i. favourable genes/alleles passed on / best adapted reproduce (more) /converse;
j. example of reproduction of individuals better adapted to changed environment;
k. alleles for adaptations to the changed environment increase in the population;
l. example of genes/alleles for adaptations increasing in a population;
m. evolution by natural selection;
n. evolution is (cumulative) change in population/species over time / change in allele frequency;
Outline the types of evidence that can be used to support the theory of evolution.
a. fossils (give evidence of evolution);
b. fossils show different species existed in the past/species changed over time;
c. selective breeding of (domesticated) animals/crop plants;
d. selective breeding shows that (artificial) selection can cause rapid change;
e. homologous (anatomical) structures/vestigial organs (give evidence of evolution);
f. homologous structures/pentadactyl limbs/other example show common ancestry;
g. DNA/base/amino acid sequences show (common) ancestry/species diverged;
Describe, using one example, how homologous structures provide evidence for evolution.
a. similar structure but different function «in homologous structures»
b. pentadactyl limbs/limb with five digits/toes / other example
c. similar bone structure/example of similarity of bones «in pentadactyl limbs» but different
uses/functions
d. two examples of use of pentadactyl limb by a vertebrate group
e. suggests a common ancestor «and evolutionary divergence»
f. process called adaptive radiation
Outline the evidence for evolution provided by selective breeding.
a. crop plants/domesticated animals/livestock produced by selective breeding
b. specific example of a domesticated animal/crop plant and the wild species from which it
was developed
or pecific example of a domesticated animal/crop plant and the features in it which have been
improved «compared with the wild species»
For example dogs have been developed from wolves:
c. artificial selection/crossing selected varieties/eliminating undesirable varieties
d. «selective breeding/artificial selection can cause» significant/rapid change over time/from the
original wild species
e. «changes due to selective breeding/artificial selection» shows natural selection can cause
change/evolution «in a species»
Explain two examples of evolution in response to an environmental change.
For each examples
a. a named example of a species that has evolved in this way;
b. description/clear statement of the change that occurred in the environment;
c. description/clear statement of different varieties (that existed at the same time);
d. explanation of/reason for one variant having a selective advantage;
e. the change in the population/species due to natural selection/evolution;
Do not award the last mark if the change is explained using Lamarckism rather than natural
selection.
Example:
f. Staphylococcus aureus/MRSA/Clostridium difficile/other named species;
g. introduction/use of an antibiotic/named antibiotic;
h. some bacteria were resistant and others were not;
i. resistant bacteria survived (and multiplied) while non-resistant were killed;
j. percentage of the population showing resistance increased;
[8] can be awarded if the candidate scores [5] for one example and [3] for the other.
Do not accept examples where the evidence of evolution comes from fossils, or where the
variation is not heritable.
Define evolution.
(cumulative) change in heritable/genetic characteristics of a population;
new species arise from pre-existing species;
change/adaptation of a population due to natural selection / descent with modification;
List two factors that could cause an increase in the size of an animal population.
a. natality / increased birth rate;
b. immigration;
c. extra food/water / breeding sites;
d. expanding habitat;
e. lack of predators/disease/parasites / reduced death rate;
Outline how antibiotic resistance in bacteria can arise in response to environmental change.
antibiotic resistance can be inherited;
alleles for resistance can be passed from one cell to another by exchange of
plasmids/conjugation;
some varieties are more resistant than others;
bacteria reproduce very rapidly and have high mutation rate;
evolution can occur rapidly;
increased exposure to antibiotics is the environmental change that selects for resistant varieties;
for example, in hospitals / animal feed / inappropriate prescriptions / not finishing prescriptions;
bacteria without resistance die / resistant bacteria survive and pass on genes to next generation;
results in change in genetic makeup of population;
Using simple external recognition features, distinguish between the plant phyla bryophyta and
angiospermophyta.
Bryophytes have scales whereas Angiospermophytes have true leaves
Bryohpytes have a waxy cuticle whereas angiospermophytes have no cuticle
State two characteristics that identify lice as members of the arthropoda.
a. jointed appendages
b. «chitinous» exoskeleton
c. segmented body / bilateral symmetry
or mouth and anus
or paired appendages
Discuss which hypothesis is a better explanation of the theory of evolution by natural
selection.
a. «scientists would accept» hypothesis A as the better one as mutations are random
b. scientists would reject hypothesis B because characteristics acquired during the lifetime of the
individual being inherited is Lamarckian/not part of the evolution by natural selection theory/not
all mutations are heritable
c. «the resistance» mutation would be present in the population initially and not caused by the
shampoo «as hypothesis B states»
d. both hypotheses include variation in the population of lice «resistant and non-resistant»
e. variation is necessary for natural selection to occur
f. frequency of the best adapted increases and these individuals reproduce/pass on resistance to
their offspring, so the resistant population increases «so hypothesis A is better»
State an external feature that is different in:
Cnidaria and Mollusca.
Cnidaria have radial symmetry while Mollusca have bilateral symmetry;
Cnidaria have tentacles/nematocysts/stinging cells while Mollusca do not;
Mollusca (may) have a (hard) shell while Cnidaria do not;
Mollusca have a mouth and anus while Cnidaria have only one opening;
Mollusca have a muscular/large foot while Cnidaria do not;
other valid external difference;
Mollusca and Annelida
Annelida are segmented while Mollusca are not (visibly segmented);
Annelida may have bristles/chetae/chaetae while Mollusca do not;
Mollusca (may) have a (hard) shell while Annelida do not;
Mollusca have a muscular/large foot while Annelida do not;
other valid external difference;
Distinguish between bryophyta and coniferophyta.
Plants are a diverse group of eukaryotic organisms. Describe the different characteristics of
the bryophyta, filicinophyta, coniferophyta and angiospermophyta.
bryophyta have no roots / only have rhizoids;
bryophyta have simple leaves/stems / only a thallus;
bryophyta produce spores in capsule;
byrophyta are nonvascular;
bryophyte exhibit (pronounced) alternation of generations / a significant gametophyte
generation;
filicinophyta have roots, stems and leaves;
filicinophyta (often) have divided/pinnate leaves;
filicinophyta produce spores in sporangia/spores on the undersides of leaves;
filicinophyta exhibit alternation of generations;
filicinophyta have primitive vascular tissue / no true xylem and phloem;
coniferophyta have woody stems;
coniferophyta (often) have narrow leaves/needles/scales;
coniferophyta produce seeds in cones/unenclosed seeds;
angiospermophyta have flowers;
angiospermophyta have ovules in ovaries;
angiospermophyta produce seeds (with hard coats) in fruits;
State all the organisms shown above that belong to the following phyla.
Filicinophyta: Fern
Arthropoda: Spider, Ant, Crab
Mollusca: Snail
Outline the use of the binomial system of nomenclature in Oryza sativa.
a. first name/Oryza for genus / second name/sativa for species;
b. (all) members of Oryza satica share special/unique features;
c. two names make a unique combination to designate species / worldwide recognizable
nomenclature;
d. varieties (japonica and indica) have some (consistent) differences (in tolerance);
Living organisms have been placed in three domains: archaea, eubacteria and eukaryote.
Distinguish archaea from eubacteria.
List two types of evidence used to determine which species belong in the same clade.
a. DNA/base sequences (of a gene/genes)
b. amino acid sequences (in a protein/proteins)
Elf Owl belongs to the domain Eukaryote.
The phylum is Filicinophyta
State the organism most closely related to the lizards.
Tuatara
Based on the taxa shown, deduce a difficulty in gathering data to study turtle ancestry.
Some taxas are extinct / convergence «of body form» could have occurred (confusing
interpretation of the data)
Molecular evidence is often used to construct a cladogram. Describe one type of
molecular-based evidence to identify members of a clade.
a. base sequences of a gene/DNA/mtDNA
OR
amino acid sequences of a protein
b. species with the most similarities «in base sequence/amino acid sequence/genomes» have
recently diverged/a common ancestor/are closely related
OR
members of a clade accumulate the fewest mutations on same base sequences/ vice versa
Suggest one type of additional evidence that could provide strong support for Turtles 3 as the
evolutionary route for turtles rather than Turtles 1 or Turtles 2.
Fossils / comparative anatomy / homologous structures / vestigial structures
Taxonomists aim to place species into genera, families and higher taxa according to their
evolutionary origins. This is known as natural classification. Explain the usefulness of
natural classification in biodiversity research.
a. «because» it allows easier identification of a species
b. «because» it can help identify common ancestors/evolutionary paths/close relationships
(showing degree of biodiversity) / OWTTE
c. «because» it is universal/cross-cultural language that avoids problems of local names of
organisms or
«because» it promotes international collaboration or
«because» it facilitates access to the history/background of the species /indexing for retrieval of
relevant «taxonomic» information / OWTTE
d. «because» it allows «biodiversity» research of larger taxa «ie examination of a family of large
cats rather than one species»
Using the cladogram, identify one diagnostic feature that characterizes the given groups of
vertebrates at A, B and C.
A: gills or fins or scales or no limbs or external fertilization
B: homeothermic or endothermic or warm-blooded or lungs or tetrapod or four limbs or
pentadactyl limbs or internal fertilization
C: hair or fur or mammary glands or milk
State the name of the domain to which these organisms belong: Eukaryotes
Outline the process of adaptive radiation.
a. ancestral species occupies new environment / survives natural disaster;
b. different members of the species are exposed to different selection pressures;
c. gives rise to new species that share common structures adapted to new environment / occupy
all niches;
d. example of divergent evolution/homology;
e. accept valid example eg Galapagos finches, vertebrate pentadactyl limb; new species evolve
from one ancestral species;
species evolve in different ways to become adapted to different ecological roles;
migration of a species to an area with a variety of niches;
natural selection/selection pressure will be different in various niches causing adaptation of
groups to the varied niches;
results in many species from one ancestral species;
reproductive isolation enhances adaptive radiation;
adaptive radiation results in speciation;
limb bone pattern of mammals shows the same basic arrangement;
derived from common ancestor/homologous structures;
common ancestral pattern adapted to different environment conditions;
suitable example; (eg wing of bat adapted for flight and limbs of mole for digging)
There has been a change of thinking; moving from gradualism to punctuated equilibrium
demonstrates the changing nature of science. Discuss these two ideas about the pace of
evolution.
in gradualism evolution occurs at a constant pace;
fossil records of gradual change with intermediate forms support this theory;
evolution of modern horse/another suitable example seems to support this view;
in punctuated equilibrium evolution proceeds rapidly for short periods of time intermittent with
long periods of little change/stability;
gaps in the fossil record/lack of intermediate forms support the idea of punctuated equilibrium;
strata in the fossil record with appearance of many new species following a mass extinction
supports the idea of punctuated equilibrium;
Define analogous characteristics using one example to illustrate your answer.
analogous structure similar in appearance/function but with different evolutionary history e.g.
wing of bat and wing of bird;
List two anatomical features that define humans as primates.
opposable thumb;
large range of shoulder movement;
good vision / stereoscopic vision / overlapping field view;
large brain relative to body size;
tailless primate;
Y-5 cusps of molars;
Define the term clade.
a group of related organisms sharing a common ancestor / a group of organisms containing an
ancestor and all of its descendants
Distinguish between analogous and homologous structures, giving an example of each.
homologous structures evolved from a common ancestor while analogous structures did not;
example of homologous and example of analogous; (both needed)
Analogous structures have the same function whereas homologous structures could have the
same or a different function. Analogous structures differ in fundamental structures whereas
homologous structures do not
Explain how the ability of a butterfly to escape from predators could increase by natural
selection.
Natural selection favours survival of better-adapted individuals;
better-adapted butterflies have greater ability to escape predation;
and survive to reproduce;
allowing them to pass their characteristics/alleles/genes to offspring;
over generations, the number of butterflies with best-escaping ability increases in the population
/ frequency of alleles/genes for better
escaping ability increases in the population/gene pool;
State two characteristics that permit the classification of microbes into domains.
cell wall structure/composition / whether the cell wall contains peptidoglycan;
size of / 70S or 80S ribosomes;
(base sequence in) ribosomal RNA/rRNA;
whether there are introns;
whether there are histone proteins;
membrane structure / ether or ester bonds (in membrane lipids);
Discuss the definition of the term species.
a species is a group of organisms with similar characteristics, which can interbreed and produce
fertile offspring;
sibling species may show similar characteristics but cannot interbreed (e.g. Pipistrelle bat in
Britain);
some pairs of species are different but can interbreed (e.g. ruddy duck and white headed
duck/many plant species);
some species always reproduce asexually so definition may not apply;
some breed in zoos/captivity, but will not interbreed in nature;
difficult to classify fossils as cannot decide if they could interbreed;
State the names of the three domains, giving a microbial example of each.
Eubacteria/Bacteria: E. coli / Pneumococcus / another suitable example; (scientific/common
name acceptable)
Archaea: methanogens / thermophiles / another suitable example;
Eukaryota: Paramecium / yeast / another suitable example;
Explain the reasons for the reclassification of Prokaryotes and Eukaryotes into Eubacteria,
Archaea and Eukaryota.
studies of (base sequences of) rRNA provided evidence for three domain classification;
differences in cell walls / Archaea and Eukaryotes have no peptidoglycan in cell wall, Eubacteria
do have peptidoglycan in cell wall;
differences in membrane bonding compared to Eubacteria and Eukaryotes / Archaea have ether
bonds in lipid membranes whereas others do not;
presence or absence of histone proteins / histone proteins present in all Eukaryotes, present in
some Archaea, none in Eubacteria;
large diversity of the group categorized as prokaryotes prompted division into two domains;
similarities between Archaea more similar to Eukaryota than to Eubacteria;
facilitates study of origin/evolution of eukaryotes;
Distinguish between Archaea and Eukarya.
a. membrane-bound organelles present in Eukarya but absent in Archaea;
b. 70S ribosomes in Archaea whereas 80S ribosomes in (cytoplasm of) Eukarya;
c. nuclear envelope in Eukarya, not in Archaea;
d. introns are present in Eukarya but only in some genes of Archaea;
e. histone proteins present in all Eukarya but only in a few Archaea;
f. the membrane lipid structure is unbranched in Eukarya but branched in Archaea;
g. Archaea can inhabit extreme habitats while Eukarya cannot;
I. peptidoglycan;
II. outer membrane/layer of lipopolysaccharide and protein;
III. peptidoglycan;
Outline how variations in specific molecules can lead to phylogeny.
a. phylogeny is the evolutionary line of descent;
b. the study of similar molecules in two different species; (e.g. mitochondrial DNA / hemoglobin
/ Cytochrome c)
c. the greater the differences, the longer the time span since the two species had a common
ancestor;
d. variation can be due to mutations;
e. mutations are chance events so caution must be taken when interpreting these;
Outline the value of classifying organisms.
a. organization of data helps to identify organisms;
b. suggests evolutionary links;
c. suggests the closeness of a relationship the more similar the characteristics are;
d. allows prediction of characteristics shared by members of a group;
Distinguish between the two domains of prokaryotes.
Archaea have different rRNA to Eubacteria;
Eubacteria have no proteins associated with DNA whereas Archaea have / vice versa;
introns are present in some genes of Archaea, but are rare/absent from Eubacteria;
cell walls are made of peptidoglycan in Eubacteria but not in Archaea;
cell membranes are made of different molecules / Eubacteria have glycerol-ester lipids whereas
Archaea have glycerol-ether lipids;
Explain cladistics as a method of classifying organisms.
a. cladistics uses cladograms/tree diagrams;
b. show clades/branches (in parallel) that begin at a point/node;
c. each clade includes a (common) ancestral organism/node and all its descendents;
d. members of a clade share derived/inherited characteristics;
e. clades are nested/subsets of larger clades;
f. cladograms show evolutionary history/origin of organisms / phylogeny;
g. branch length (of clade) can indicate (relative) amount of genetic change/time;
h. clades based on (objective) molecular analysis/genetic evidence / differ in amino acid
sequences/DNA base changes/mutations;
i. fewest number of differences/maximum parsimony determines branch separation;
j. predictability of DNA base changes/mutation rates suggests evolutionary timelines;
k. problems arise when gene change varies (greatly) from one gene to the next;
l. cladograms may not match traditional/Linnaean classification;
m. (mismatch) prompts re-examination of data / reclassification of a group;
Discuss the use of cladograms in phylogenetic studies.
a. a cladogram is a diagram which shows shared characteristics/phylogenetic relationships;
b. phylogeny is the study of evolutionary origins/ancestry;
c. clade is a group of (all) organisms that evolved from a common ancestor;
d. evidence from biomolecules/DNA/RNA/protein/cytochromes;
e. cladograms can be compared with other representations of phylogenetic relationships/may
confirm fossil/anatomical evidence;
f. organisms placed close together in a cladogram are closely related evolutionarily;
g. there may be more than one possible cladogram (for a particular group) raising questions
about evolutionary relationships;
h. divisions between clades/nodes suggest the sequence in which groups diverged;
i. cladograms can be used to estimate time since groups diverged;
j. cladograms are often similar to classification based on other evidence/traditional methods;
k. cladograms may lead/have led to reclassification of a group;
On the cladogram, label with the letter C the point that shows the most recent common
ancestor of Pambdelurion and Fuxianhuia.
Explain the biochemical evidence for the common ancestry of organisms on Earth.
all organisms use DNA as genetic material;
same four (nucleotide) bases makes up DNA in all organisms;
number of mutations reflect differences between organisms;
all organisms use the same genetic code / minor differences;
genetic code is degenerate/OWTTE;
all organisms use the same 20 amino acids;
function of proteins constant between species;
protein/molecule examples; (eg hemoglobin, cytochrome, chlorophyll)
only left-handed amino acids have been observed in living organisms;
although right-handed amino acids will have been available;
only right-handed glucose/carbohydrates used in organisms;
similarities in glycolysis/metabolic pathways;
all use RNA/same enzymes in transcription/translation;
amino acids all L- not D- isomers;
Distinguish between innate and learned behaviour.
innate behaviour is independent of experience/environmental conditions/inherited
while learned behaviour is influenced by experience/environment
A is the most similar to B
A is equally similar to C and D
A is the least similar to C and D both
Suggest two reasons for using cladograms for the classification of organisms.
methods used to prepare cladograms use a different approach from traditional
classification/taxonomy;
show ancestral relationships;
reflect how recently two groups shared a common ancestry;
cladograms are (objective/accurate because they are usually) based on molecular differences;
they should be considered as a good complement to traditional classification;
Outline how open reading frames are identified in DNA.
a. identify a start codon and stop codon
b. identify base sequences for a gene/that could code for a polypeptide
c. possible correlation with existing open reading frames in databases
Explain what the branching off points represent in the cladogram of these fungi.
a. represent common ancestors shared by the organisms that emanate from the point
b. indicates time since divergence
c. indicates number of differences in DNA
Chapter 6
Explain how the small intestine moves, digests and absorbs food.
a. contraction of muscle layers /peristalsis helps move food. The circular muscle contraction
prevents backward movement of food, longitudinal muscle contraction moves food along gut
b. peristalsis/muscle contractions mix food with intestinal enzymes
c. enzymes digest macromolecules into monomers
d. pancreatic enzymes/amylase/lipase/endopeptidase chemically digest food in the lumen of the
small intestine
e. pancreatic amylase digests starch
lipases digest triglycerides
endopeptidases/dipeptidases digest proteins/polypeptides
f. bile is secreted into the small intestine creates favorable pH for enzymes
bile emulsifies fat
g. some final digestion into monomers is associated with epithelial cells/epithelium of small
intestine
h. mucosa layer /lining of small intestine contains villi/finger-like projections
i. villi/microvilli increase surface area for better absorption
j. villi absorb products of digestion which are mineral ions / vitamins
k. glucose/amino acids enter blood capillaries
lipids enter lymph vessels/lacteals
l. absorption involves active transport/diffusion/facilitated diffusion
m. different nutrients are absorbed by different transport mechanisms
Outline how leptin controls appetite.
a. leptin suppresses/inhibits appetite
b. is secreted by adipose tissue
c. level is controlled by amount of adipose tissue/ongoing food intake
d. leptin targets cells in hypothalamus which is the appetite control centre in brain
e. causes hypothalamus to inhibit appetite
f. if amount of adipose tissue increases, blood leptin concentration rises
Discuss the roles of the enzymes secreted by the pancreas during digestion.
a. amylase hydrolyses starch to maltose
b. lipase hydrolyses fats to fatty acids and glycerol
c. proteases/peptidases hydrolyze proteins into smaller polypeptides, dipeptides or amino acids
Explain how the structure of a villus in the small intestine is related to its function. Explain
how the structure of the villus is adapted for absorption.
a.
b.
c.
d.
e.
f.
g.
h.
i.
the villus has a large surface area to volume ratio;
microvilli increase surface area for absorption;
thin surface epithelial layer so products of digestion can pass easily through;
channel proteins located in plasma membrane used for facilitated diffusion;
network of capillaries inside each villus so only short distance for movement of absorbed
products;
capillaries transport absorbed nutrients/sugars and amino acids away from small intestine;
blood flow in capillaries maintains concentration gradient;
central lymph vessel/lacteal to transport absorbed fats/fatty acids away from small
intestine;
large number of mitochondria provide ATP needed for active transport;
j. protein pumps in membrane of microvilli carry out active transport;
k. pinocytosis occurs at surface epithelial layer;
Outline the digestion, absorption and assimilation of proteins in humans.
a.
b.
c.
d.
e.
large molecules proteins must be digested into small molecules;
a protease/pepsin digests proteins into polypeptides;
pepsin works in the stomach / requires an acid/low pH/pH 2 to work;
polypeptides are digested by a protease/trypsin into amino acids;
trypsin acts in the small intestine / requires a basic pH/pH 8/high pH;
f.
g.
h.
i.
j.
amino acids absorbed by diffusion/active transport;
absorption occurs in the villus/microvilli of the small intestine;
amino acids absorbed into capillaries;
blood carries amino acids throughout the body;
amino acids diffuse into cells/are absorbed by active transport;
k. cells use amino acids to build proteins;
l. assimilation is when amino acids become part of a cell;
m. proteins are synthesized at the ribosomes/ER of the cell;
Plants store carbohydrate in the form of starch. Explain the reasons for starch being digested
by the human digestive system.
a.
b.
c.
d.
e.
f.
g.
starch is a large molecule;
large molecules/starch cannot be absorbed by the intestine/villi/epithelial cells;
glucose produced by digestion of starch can be absorbed;
starch/glucose is a useful source of energy;
starch is not used in humans;
glucose is stored as glycogen not starch;
starch is not soluble/could not be transported by blood;
Explain the importance of enzymes to human digestion. Outline the need for enzymes in the
digestive system.
a.
b.
c.
d.
e.
food must be in a small enough form to leave the gut and enter the bloodstream;
physical breakdown is not enough / chemical breakdown is necessary;
enzymes are required for the chemical breakdown of food;
enzymes increase the rate of digestion;
enzymes are biological catalysts;
f. enzymes allow digestion to occur at body temperature;
g. enzymatic digestion is a sequential process e.g. from protein to peptide to amino acid;
h. specific location for each reaction with specific conditions/environments e.g. stomach
high acidity;
i. most enzymes work extracellularly / some enzymes work intracellularly;
j. variations in pH throughout digestive tract promote the activity of different digestive
enzymes / different enzymes have different optimal pHs;
k. amylases digest carbohydrate to monosaccharides;
l. proteases digest proteins to amino acids;
m. lipases digest fats to fatty acids and glycerol;
n. make soluble products/molecules small enough to be absorbed;
State one function of the large intestine.
Reabsorb water/vitamins
Temporary storage of faeces
Describe the digestion of food in the human digestive system.
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
chewing food makes smaller particles/increases surface area of food;
starch digestion begins in the mouth by salivary amylase
digestion of proteins in stomach;
acid condition in stomach provides optimum pH for enzymes;
stomach muscle contraction causes mechanical digestion;
enzymes in small intestine complete digestion;
alkaline condition in small intestine provides optimum pH for enzymes;
bile salts help to emulsify fats;
example of amylase with source, substrate and products;
example of protease with source, substrate and products;
example of lipase with source, substrate and products;
Outline a mechanism used to transport products of digestion from the lumen of the ileum into
the blood.
Facilitated diffusion;
substance moves from high to low concentration/ down concentration gradient;
protein channels needed;
does not require ATP/energy / passive;
valid example; eg amino acids / glucose / fructose / water soluble vitamins
Active transport;
substance moves from low to high concentration / against concentration gradient;
membrane pumps needed / Na/K pump, Ca++Ca++;
ATP/energy required;
valid example; eg amino acids / glucose / mineral irons / iron
Endocytosis/pinocytosis;
droplets of intestinal fluid surrounded by membrane;
forms vesicle;
vesicles are released inside villus cell;
valid example; eg fat soluble vitamins
State four molecules transported by the blood.
a. example of a nutrient e.g. glucose;
b. dissolved gases oxygen/O2;
c. carbon dioxide/CO2;
d. nitrogen/N2;
e. hormones;
f. antibodies;
g. urea;
Other components of blood:
plasma/water;
erythrocytes / red blood cells;
leucocytes / white blood cells;
lymphocytes and phagocytes;
platelets;
hormones / named hormone s ;
amino acids / albumin / antibodies;
salts / minerals / ions
plasma proteins;
Blood absorbs:
Oxygen in the lungs
Hormones in the endocrine glands
Carbon dioxide in cells and tissues
Outline the unconscious control of the heart rate.
heart can contract without nervous stimulation/myogenic contractions;
SA node is pacemaker/generates heart beat/initiates each cardiac cycle;
stimulates atria to contract;
leading to contraction of ventricles;
nerves carry impulses from the brain to speed up and slow down the heart;
medulla of the brain monitors blood pressure;
epinephrine/adrenalin produced by adrenal gland
carried by blood to the heart
speeds up the heart rate;
autonomic/sympathetic and parasympathetic nervous system control;
sympathetic speeds up heart rate;
parasympathetic/vagus nerve slows heart rate back to normal/resting rate ;
Describe the action of the heart in pumping blood.
a. both atria collect blood from veins ;
b. sinoatrial/SA node sends impulses to muscle/fibres initiating contraction;
c. blood is pushed to ventricles by contraction of atria/atrial systole;
d. AV atrioventricular valves are open as atria contract ;
e. semilunar valves are closed so that ventricles fill with blood;
f. ventricles contract / ventricular systole;
g. AV atrioventricular valves close preventing backflow ;
h. blood is pushed through the semilunar valves/pulmonary artery and aorta;
i. when ventricles relax /diastole, semilunar valves close preventing backflow of blood;
The pumping of blood is a vital process. Explain the roles of the atria and ventricles in the
pumping of blood.
a.
b.
c.
d.
e.
f.
atria collect blood from veins vena cava/pulmonary ;
collect blood while ventricles are contracting;
atria pump blood into ventricles/ensure ventricles are full;
ventricles pump blood into arteries/out of the heart;
ventricles pump blood at high pressure because of their thicker, muscular walls;
mention of heart valves working with atria and ventricles to keep blood moving;
g. left ventricle pumps blood to systems and right ventricle pumps blood to lungs;
Explain how circulation of the blood to the lungs and to other systems is separated in humans
and what the advantages of this separation are.
a. double circulation / pulmonary and systemic circulations
b. heart is a double pump / heart has separate pumps for lungs and other systems / left and right
sides of heart are separate / no hole in heart after birth
c. deoxygenated blood pumped to the lungs and oxygenated to other organs/tissues/whole body
apart from lungs
d. each side of the heart has an atrium and a ventricle
e. left ventricle pumps blood to the systems/tissues and right ventricle pumps blood to the lungs
f. left atrium receives blood from the lungs and right atrium receives blood from systems/tissues
g. left ventricle pumps blood via the aorta and right ventricle pumps blood via the pulmonary
artery
h. left atrium receives blood via the pulmonary vein and right atrium receives blood via the vena
cava
i. lungs require lower pressure blood / high pressure blood would damage lungs
j. high pressure required to pump blood to all systems/tissues apart from lungs
k. pressure of blood returning from lungs not high enough to continue to tissues / blood has to be
pumped again after returning from lungs
l. oxygenated blood and deoxygenated blood kept separate / all tissues receive blood with high
oxygen content/saturation
Explain how the direction of blood flow in the heart is controlled.
valves open/close due to blood pressure differences;
valves prevent backflow/only allow unidirectional flow;
atrioventricular valves between ventricles and atria;
semilunar valves between arteries and ventricles;
Distinguish between the vein and the artery with reference to structures visible in the
micrograph.
a. vein has larger lumen
b. vein has less elastic tissue
c. vein has less muscular/thinner walls/tunica media/ratio of wall thickness to lumen is less in the
vein
d. vein less rounded/squashed more easily
Outline the exchange of materials between capillaries and tissues.
a. molecules move by diffusion / move down a concentration gradient
b. nutrients move into tissues
c. gas exchange / Oxygen and carbon dioxide exchange between tissues and blood/capillaries
d. nitrogenous wastes/excess water move from cells/tissues into blood/capillaries
e. hormones leave capillaries in target tissues/to attach to receptors on cells / endocrine
organs/gland tissues release hormones into the bloodstream
Explain the relationship between structure and function of arteries, capillaries and veins.
Arteries:
a. thick walls to withstand high pressure/maintain blood flow/pressure;
b. many muscle fibres to help pump blood;
c. many elastic fibres to stretch and pump blood after each heart beat;
d. collagen fibres/elastic fibres/connective tissue in outer layer give wall
strength/flexibility/ability to stretch and recoil;
e. smooth muscle layer contracts to maintain pressure;
f. narrow lumen maintains high pressure;
g. smooth endothelium for efficient transport/reduced friction;
h. no valves as pressure is high enough to prevent backflow;
Capillaries:
a. wall has one layer of cells allowing fast diffusion of substances;
b. only one red blood cell allowed to pass at a time for efficient oxygen uptake;
c. pores between cells of the walls so plasma can leak out;
d. pores between cells of the walls allow phagocytes/immune components to enter tissues;
e. extensive branching increases surface area for exchange of materials;
f. small diameter/narrow lumen to fit into small places/between cells;
g. small diameter allows them to fit between cells/perfuse tissue;
h. narrow diameter increases oxygen diffusion from RBC;
Veins:
k. thin walls allow skeletal muscles to exert pressure on veins;
l. thin outer layer of collagen/elastic/muscle fibres provide structural support;
m. wide lumen allows great volume of blood to pass;
n. valves prevent backflow;
Function of goblet cell is secretion/exocytosis. A goblet cell is not likely to divide as it is
specialized/differentiated or as the nucleus is in interphase/not in mitosis
Outline the exchange of materials between capillaries and tissues.
a. molecules move by diffusion / move down a concentration gradient
b. nutrients move into tissues
c. gas exchange / Oxygen and carbon dioxide exchange between tissues and blood/capillaries
d. nitrogenous wastes/excess water move from cells/tissues into blood/capillaries
e. hormones leave capillaries in target tissues/to attach to receptors on cells / endocrine
organs/gland tissues release hormones into the bloodstream
Describe what happens in alveoli.
a. gas exchange
b. oxygen diffuses from air to blood and carbon dioxide diffuses from blood to air
c. oxygen binds to hemoglobin in red blood cells
d. pressure inside/volume of alveoli increases as air enters and decreases as air exits alveoli
during ventilation
e. blood flow through capillaries
concentration gradients of gases/oxygen/CO2 maintained
f. type II pneumocytes secrete fluid/surfactant / secretion of surfactant to prevent sides of
alveolus adhering
Define tidal volume and ventilation rate.
a. tidal volume: volume of air taken in with each inhalation/out with each exhalation;
b. ventilation rate: number of inhalations/exhalations/breaths per minute;
Explain the processes that control changes in ventilation rate during exercise.
a. exercise increases aerobic respiration;
b. CO2 concentration in blood increases;
c. drop in pH of blood detected / blood more acidic;
d. medulla / breathing centres send impulses to diaphragm and intercostal muscles;
e. increase rate of contraction;
f. increase in ventilation rate increases oxygen uptake for aerobic cell respiration
g. It also increases the rate of removal of CO2;
Explain the change in the tidal volume during exercise.
a. exercise increases / results in higher rate of respiration
b. exercise produces more carbon dioxide / consumes more oxygen
c. increased tidal volume excretes more carbon dioxide / obtains more oxygen
d. increased tidal volume increases gas exchange across alveoli
e. concentration gradients of gases is maintained
Active skeletal muscle requires a good supply of oxygen. Outline the mechanism of ventilation
in the lungs.
a. ventilation is movement of air into and out of lungs;
b. volume of thorax and pressure in thorax are inversely related
c. air flows from higher to lower pressure until the pressures are equal;
d. a concentration gradient between air sacs and blood needs to be maintained;
during inhalation:
a. external intercoastal muscles contract moving rib cage up and out;
b. diaphragm contracts becoming lower/flatter;
c. internal intercostal/abdomen wall muscles relax;
d. increase in volume and decrease in pressure of thorax ;
e. air flows into lungs as atmospheric pressure is higher than pressure in lungs
during exhalation:
e. internal intercostal muscles contract so ribs move in and down;
f. diaphragm relaxes and returns to domed shape;
g. decrease in volume and therefore increase in pressure of thorax;
h. air moves out until pressure in lungs falls/is equal to atmospheric pressure;
i. abdominal muscles can be used to make a stronger/forced exhalation;
j. recoil of elastic fibres that stretched during inspiration;
k. internal intercostal muscles contract during forced ventilation ;
Describe the effects of training on the pulmonary system.
a. ventilation rate at rest is reduced;
b. maximum ventilation rate during exercise increases;
c. diaphragm and intercoastal muscle strength increase;
d. vital capacity may increase/ VO2 max may increase;
Describe the need for a ventilation system in humans.
a. most cellular respiration is aerobic/requires oxygen / produces carbon dioxide;
b. ventilation system exchanges gases between inhaled air blood stream;
c. ventilation system maintains high concentration gradient of gases in alveoli/ lungs;
A supply of oxygen is needed for aerobic respiration in mitochondria. Describe the features of
alveoli in human lungs that adapt them for efficient absorption of oxygen.
a. large surface area from having many alveoli;
b. single/flattened layer of thin cells in wall;
c. surrounded by dense network of capillaries/capillary bed;
d. short distance for gases/oxygen/carbon dioxide to diffuse;
e. moist lining / film of moisture on inside of alveolus;
f. moisture allows oxygen/gases to dissolve;
g. diffusion of oxygen down concentration gradient;
Distinguish between ventilation, gas exchange and cell respiration.
a.
b.
c.
d.
e.
f.
ventilation is moving air into and out of lungs/inhalation and exhalation;
involves respiratory muscle activity;
gas exchange involves movement of carbon dioxide and oxygen;
between alveoli and blood in capillaries / between blood in capillaries and cells;
cell respiration is the release of energy from organic molecules/glucose;
aerobic cell respiration occurs in mitochondria;
All motor neurons use acetylcholine to activate skeletal muscle. Explain the effect of
neonicotinoid pesticides in insect synapses in the central nervous system.
a. Neonicotinoid pesticides are similar to nicotine chemically
b. Neonicotinoid pesticides are able to irreversibly bind to nicotinic acetylcholine receptors
and trigger a sustained response
c. Neonicotinoid pesticides cannot be broken down by acetylcholinesterase
d. Prevents/blocks acetylcholine binding
e. Blocks transmission from CNS
f. blocks signals going to muscle
g. muscle contraction blocked
h. causes paralysis
Resistance to neonicotinoid pesticides has been observed in some insects. Describe briefly how
this resistance could have arisen in populations of insects.
a. Mutations for resistance in some insects
b. Mutation causes breakdown of pesticide/detoxification of pesticide/changes to receptor
site
c. Natural selection for resistance: Resistant insects survive and reproduce;
Non-resistant killed leaving only resistant insects
Nerves connecting the brain and heart contain neurons that control heart rate. Explain how a
nerve message passes from one neuron to another neuron.
a. nerve impulse reaches the end of the presynaptic neuron;
b. depolarization causes calcium channels in membrane to open;
c. calcium diffuses into the presynaptic neuron;
d. vesicles of/containing neurotransmitter move to and fuse with presynaptic membrane;
e. neurotransmitter released by exocytosis into synaptic space/cleft;
f. neurotransmitter diffuses across the space/synapse;
g. neurotransmitter attaches to receptors on postsynaptic neuron;
h. receptors cause ion channels to open and sodium diffuses into the postsynaptic neuron;
i. the postsynaptic neuron membrane is depolarized;
j. depolarization causes a new action potential;
k.neurotransmitter on postsynaptic membrane is broken down;
l. neurotransmitter is reabsorbed into the presynaptic neuron;
Explain how an impulse passes along the axon of a neuron.
a. resting potential is –70mV / relatively negative inside in comparison to the outside;
b. Na+/K+ pumps maintain/re-establish the resting potential ;
c. more sodium ions outside than inside when at the resting potential;
d. more potassium ions inside than outside;
e. nerve impulse is an action potential that stimulates a wave of depolarization along the
membrane/axon;
f. if neuron is stimulated/threshold potential/–50mV is reached sodium ion channels open;
g. sodium ions diffuse/move in;
h. Na+ move in causing depolarization;
i. potassium ion channels open / potassium ions diffuse/move out;
j. inside becomes negative compared with outside / potential across membrane restored /
repolarization;
k. active transport of K+ into neuron and Na+ out of neuron restores resting potential;
l. Na-K pumps restore Na/K balance/resting potential
m. Myelin around the neuron insulates the axon
n. speeds the transmission
o. Myelin permits saltatory conduction
p. permits jumping from node to node
l. local currents / description of Na+ ion diffusion between depolarized region and next region of
axon to depolarize;
Membranes of pre-synaptic and post-synaptic neurons play an important role in transmission
of nerve impulses. Explain the principles of synaptic transmission.
a. synapse is gap between adjacent neurons;
b. arriving action potential depolarizes pre-synaptic membrane;
c. opens voltage-gated calcium channels in membrane;
d. causes influx of calcium ions;
e. causes synaptic vesicles to fuse with pre-synaptic membrane;
f. vesicles release/exocytose neurotransmitter into the synaptic cleft;
g. neurotransmitter diffuses/moves across synaptic cleft;
h. neurotransmitter binds to receptors on post-synaptic membrane;
i. change in membrane permeability;
j. sodium ions flow into post-synaptic neuron;
k. opens channels allowing sodium ions/potassium ions to diffuse;
l. initiation of action potential/depolarization in post-synaptic membrane;
m. removal of the neurotransmitter; by enzyme / cholinesterase;
n. inactivated neurotransmitter returns to pre-synaptic neuron;
o. stops effect on post-synaptic membrane;
Chapter 11
Describe the functioning of immunoglobulins.
Immunoglobulins function as antibodies. They have a variety of binding sites / variable regions
for binding which are specific to antigens on bacteria/viruses/pathogens. Their constant region
aids destruction of the bacteria/virus/pathogen as the macrophages recognise this region. It helps
phagocytes/macrophages to engulf pathogen more easily.
Antibodies aid in the destruction of pathogens by a number of different mechanisms:
• Precipitation – Soluble pathogens become insoluble and precipitate
• Agglutination – Cellular pathogens become clumped for easier removal
• Neutralisation – Antibodies may occlude pathogenic regions e.g. exotoxins
• Inflammation – Antibodies may trigger an inflammatory response within the body
• Complement activation – Complement proteins perforate membranes cell lysis
Outline how antibiotics offer protection from certain forms of infectious disease.
a. protect against/kill/inhibit growth of microorganisms/bacteria/prokaryotes
b. bacteria/prokaryote processes blocked but not processes in eukaryotes/other organisms
c. block metabolic pathways/DNA replication/DNA transcription/translation/ribosome
functioning/cell wall formation
d. do not protect against viruses as they have no metabolism/are non-living
e. antibiotics fail to protect if bacteria have resistance
f. can be used in humans/animals because antibiotics do not affect eukaryotic cells/bacterial
metabolism is different.
Some blood proteins are involved in defence against infectious disease. Explain the roles of
named types of blood proteins in different defence mechanisms.
a. clotting factors are proteins that initiate the clotting cascade/process
b. fibrin is a protein that permits blood clotting / allows the formation of a clot
c. the protease thrombin converts fibrinogen to fibrin
d. fibrin forms a mesh/clot that prevents the entry of pathogen/antigen into the blood
e. antibodies are specific proteins that lymphocytes make
f. each antibody corresponds to a specific pathogen/antigen
g. antibodies create specific immunity
h. plasma cells produce large amounts of specific antibodies
i. immunoglobulins are antibodies against pathogens
j. enzymes in phagocytic white blood cells may digest pathogens
Describe the processes involved in blood clotting.
cells/tissue is damaged/cut/bruised;
damaged cells/platelets release clotting factors; cascade/series of reactions
clotting factors cause the production of thrombin by activating prothrombin
soluble fibrinogen to insoluble fibrin / thrombin converts fibrinogen to fibrin;
forms a net of fibres trapping blood cells;
forming a clot / prevents blood loss / entry of bacteria/pathogens;
cascade of reactions/series of stages prevent accidental clotting/speed up clotting;
Explain antibody production.
a. many types of lymphocytes B and T exist;
b. produced/ stored in the lymph nodes;
c. each type recognizes one specific antigen/pathogen;
d. each type responds by dividing to form a clone;
e. a clone B lymphocyte secretes specific antibody against the antigen;
f. antibodies are produced as part of a specific immune response;
g. some reference to plasma/memory cells;
a. each antibody corresponds to a specific antigen
b. antibodies are necessary for immunity/resistance to infectious disease
c. macrophage/phagocyte ingests/engulfs pathogen
d. macrophage/phagocyte digests pathogen
e. macrophage/phagocyte displays antigen from pathogen
f. antigens of a pathogen correspond to a specific T lymphocytes/cells
g. T lymphocytes/cells activate B lymphocytes/cells
h. B cells divide by mitosis to form many/clones of plasma cells
i. plasma cells secrete specific antibody
j. some activated B lymphocytes/cells act as memory cells
Explain the principles of vaccination.
a. vaccines contain a dead/weakened form of the pathogen/bacteria/virus;
b. vaccine introduced to the body by injection/on surface of skin/orally;
c. antigens in the vaccine cause antibody production;
d. antigen/pathogen engulfed by macrophage/phagocyte;
e. each type of lymphocyte recognizes specific antigen;
f. macrophages activate helper T-cells;
g. which activate B-cells;
h. B-cells divide to form clones/memory cells;
i. B-cells divide to form plasma cells/antibody producing cells;
j. result is specific immunity;
k. vaccination/first exposure causes slow production of antibodies and lower level of antibodies;
this idea can be illustrated on a diagram or graph
l. contact with the disease leads to rapid production and higher level of antibodies; this idea can
be illustrated on a diagram or graph
m. second/booster shot to stimulate memory cells/more production of antibodies;
Explain why antibiotics are effective against bacterial diseases but not against viral diseases.
a. antibiotics block metabolic pathways of bacteria / reference to a specific pathway;
b. viruses have no metabolic pathways / viruses reproduce using the host cell’s metabolic
pathways;
c. host cell’s metabolic pathways are not affected by antibiotics / antibiotics do not affect host
cells because they are metabolically different from bacteria;
Bacteria are prokaryotes that sometimes act as pathogens. Describe how the body can defend
itself against pathogens.
a. skin/mucus membranes act as barrier to pathogens ;
b. sebaceous glands secrete lactic acid/fatty acids/sebum / make surface of skin acidic;
c. skin/stomach acid prevents growth of many pathogens;
d. lysozyme in mucus can kill bacteria;
e. pathogens caught in sticky mucus and removed from body;
f. inflammatory response/inflammation can cause swelling/redness/fever to inhibit the pathogen ;
g. phagocytes/macrophages/leucocytes/white blood cells non-specifically identify
pathogens/bacteria/fungi/viruses as foreign;
h. phagocytes macrophages/leucocytes/white blood cells ingest pathogens;
i. specific lymphocytes recognize one specific antigen;
j. antigen-specific lymphocytes clone themselves;
k. lymphocytes/leucocytes produce antibodies;
l. antigen-antibody complex formed and stimulates destruction of pathogen;
Explain the evolution of antibiotic resistance in bacteria.
a. antibiotics are chemicals used to treat bacterial diseases;
b. within populations, bacteria vary in their genetic resistance to antibiotics/fitness;
c. resistance arises by random gene mutation;
d. when antibiotics are used antibiotic-sensitive bacteria are killed;
e. natural selection favours those with resistance;
f. resistant bacteria survive, reproduce and spread the gene / increase allele frequency of resistant
bacteria;
g. the more an antibiotic is used, the more bacterial resistance/the larger the population of
antibiotic-resistant bacteria;
h. genes can be transferred to other bacteria by plasmids;
i. doctors/vets use different antibiotics but resistance develops to these as well;
j. multiple-antibiotic resistant bacteria evolve/it becomes difficult to treat some infections;
Outline how leucocytes defend the body against pathogens.
a. leucocytes/phagocytes/macrophages can recognize pathogens/foreign matter;
b. phagocytes engulf pathogens by endocytosis/phagocytosis;
c. migration to tissues/squeezing out of capillaries; attraction to foreign protein/pathogen /
chemotaxis;
membrane invaginates / engulfs foreign matter / phagocytosis/endocytosis;
formation of vacuole/vesicle;
phagocytes can squeeze out of walls of capillaries;
d. each pathogen has specific antigens;
e. leukocytes/lymphocytes produce antibodies by reacting to specific antigen/ pathogens;
f. antibody joins to specific antigen inactivating/destroying them;
g. lymphocyte makes a clone/copies itself;
h. thus increasing the total number of specific antibodies;
Discuss the cause, transmission and social implications of AIDS.
a. AIDS caused by HIV;
b. penetrates T lymphocytes;
c. envelope glyco protein and cell receptors involved;
d. reverse transcriptase enables DNA to be produced from viral RNA; reject DNA transformed
into RNA
e. number of lymphocytes reduced over years;
f. results in lower immunity;
g. other illnesses develop as result of lower immunity ;
h. AIDS is the observed syndrome when final stages of infection develop
i. HIV transmitted through blood/sexual contact/body fluids/placenta/childbirth/ breastfeeding;
j. distribution/transmission uneven around the world;
k. transmission risk increased depending on society’s traditions/beliefs/behaviour;
l. rare minority of individuals do not have cell receptors and do not develop AIDS;
m. condoms/latex barriers only protection against transmission through sexual contact;
n. treatment expensive;
o. discrimination against victims;
p. moral obligation of wealthy countries to help poorer countries;
q. economic consequences / loss of wage earners etc.;
r. increase in the number of orphans;
s. comment on traditions/beliefs/behaviour; if not already awarded in transmission
Outline how monoclonal antibodies are produced.
B lymphocytes are produced in laboratory animal after injection with an antigen. These animal
cells/these cells are fused with tumour cells to form hybridomas which produce antibodies.
Discuss how the HIV virus is transmitted.
HIV virus transmitted by body secretions/semen/blood/across placenta. It could be
transmitted by infected blood transfusions/intravenous drug users and mainly by sexual
activity/promiscuity.
Outline the principle of immunity.
Immunity is the ability of an organism to resist infection due to presence of specific antibodies.
Immunity can be active or passive. Passive due to receiving antibodies from external
sources/across placenta/from breast milk/injection and active results from facing an infection
directly/through vaccination. The pathogen/foreign cell invades body, leads to clonal
selection/formation of B memory cells which produce specific antibodies. If same pathogen
enters body again memory cells activated/stimulated to divide and antibodies produced faster and
in greater amounts.
Define the term passive immunity.
the acquisition of antibodies from another organism
Discuss the benefits and dangers of vaccination.
Benefits:
immunity results
can limit pandemics/epidemics/spread of infectious diseases;
diseases can be eradicated/smallpox eliminated;
reduces mortality/deaths due to disease;
can protect vulnerable groups/young/old/with other conditions;
decrease crippling effects of diseases such as polio ;
decreased health care costs;
Dangers:
may produce mild symptoms of the disease;
human error in preparation/storage/administration of vaccine;
individual may react badly to vaccine / defective immune system / hypersensitive/allergic
reaction;
immunity may not be life-long/booster required;
possible toxic effects of mercury-based preservatives/thimerosal;
Describe the production of hybridoma cells.
An animal typically a mouse is injected with an antigen and produces antigen-specific plasma
cells. The plasma cells are removed and fused hybridised with tumor cells capable of endless
divisions immortal cell line . The resulting hybridoma cell is capable of synthesising large
quantities of monoclonal antibody.
Uses of hybridoma cells: Also uses of monoclonal antibodies:
Produce monoclonal antibodies
Diagnosis of diseases; malaria, HIV, cancer
Pregnancy testing
Treatment of tissues
Blood and tissue typing
Targetting of cancer cells with a chemotherapy drug
Treatment of infection if too late for vaccination
Explain muscle contraction.
a. myofibrils in muscle fibers/cells
b. sarcomeres are the repeating units in muscle/myofibrils ü
c. sarcomeres arranged end to end / sarcomeres shorten during muscle contraction
d. actin and myosin/overlapping protein filaments/diagram to show sarcomere with actin and
myosin overlapping
e. dark and light bands in sarcomeres /diagram to show this/light bands narrower when muscle is
contracted
f. thick filament is myosin and thin filament is actin/diagram to show this
g. nerve impulses stimulate contraction/cause depolarization of sarcolemma/T-tubules/trigger
release of calcium from sarcoplasmic reticulum
h. calcium ions released from sarcoplasmic reticulum/bind to troponin
i. troponin causes tropomyosin to move thus exposing the binding sites on actin
j. myosin heads form cross bridges with/bind to actin
k. myosin heads move/change angle/swivel/cock / myosin heads cause the power stroke
l. myosin filaments pull actin towards center of sarcomere/more overlap between actin and
myosin/Z-lines move closer
m. ATP is used to provide energy /cause cross-bridges to break/cause movement of myosin
heads/cause filaments to slide/cause muscle contraction
n. intercostal/abdominal/diaphragm muscles contract to cough
Explain how skeletal muscle contracts
a. sliding filament model / filaments/actin and myosin slide past each other;
b. action potential/depolarisation/nerve impulse arrives at end of motor neurone;
c. neurotransmitter/acetylcholine released causing action potential in muscle fibre ;
d. sarcoplasmic reticulum releases calcium ions;
e. calcium ions cause binding sites on actin/for myosin to be exposed;
f. myosin heads bind to sites on actin/form cross-bridges;
g. myosin head moves actin filament using energy from ATP;
h. actin moved towards the centre of sarcomere/M line/M band;
i. sarcomeres shortened;
j. binding of ATP causes release of myosin head from actin;
k. conversion of ATP to ADP and Pi causes myosin heads to change angle;
l. cycle of events repeated during muscle contraction ;
motor neuron stimulates the muscle fibre;
calcium ions are released from sarcoplasmic reticulum ;
calcium ions bind to troponin;
tropomyosin moved / binding sites of actin revealed;
ATP binds to myosin causing cross-bridges to break;
ATP becomes ADP causing myosin heads to change angle/become cocked;
myosin heads attach to new actin sites/form cross-bridge;
ADP released;
myosin heads move actin filaments toward centre;
making sarcomere shorter;
calcium ions are reabsorbed into the sarcoplasmic reticulum ;
muscle fibre relaxess
Role of ATP
a. ATP binds to myosin heads;
b. ATP used to break cross bridges;
c. energy released when ATP forms ADP and phosphate;
d. myosin head reset;
e. actin slides over myosin;
Role of Calcium Ions
Ca2+ ions released when a nerve impulse arrives at the muscle;
Ca2+ ions are released from the sarcoplasmic reticulum;
binding sites for myosin heads are exposed; it moves the muscles blocking the myosin binding
site on actin
this allows cross-bridges between myosin and actin to form;
Outline the function of myosin and actin in muscle contraction.
a. formation of cross-bridges/myosin binds to the thin filament/actin;
b. Z-bands pulled towards each other;
c. sliding of actin and myosin filaments/shortening the sarcomere/I-band;
d. use of ATP to break cross-bridges / myosin releases actin when binding to ATP;
e. myosin heads re-set;
f. contraction ceases when myosin head detaches from the thin filament;
List two structural features of a joint that reduce friction between bones.
1. Cartilage
2. Synovial Fluid
3. Joint capsule that prevents fluid from leaking
State the role of ligaments in human movement.
They connect bones to bones, enable joint movement and prevent dislocation.
Humerus: Anchorage for attachment of muscle
Cartilage: Acts as a shock absorber
Chapter 9
In hot, dry conditions plants lose water rapidly due to transpiration. Explain how the
structures and processes of the plant allow this water to be replaced.
Evaporation of water «in leaf/mesophyll» creates tension/low pressure/negative pressure
«potential»/pulling force/transpiration pull
evaporation from spongy mesophyll cells;
replaced by osmosis from the xylem;
(diffusion of water vapour) through stomata;
Water drawn through cell walls/out of xylem «in leaf» by capillary action/adhesion «to
cellulose»
Low pressure/tension/suction/pulling force in xylem
Hydrogen bonds make water cohesive/allow water to be pulled up under tension/allow the
transpiration pull «to move water»
Xylem resists tension/low pressure/collapse with thickened/lignified walls
cellulose wall with rings of lignin give strength to resist (low) pressure;
Water travels from the roots to the leaves in xylem
Water absorbed in roots by osmosis due to higher solute concentration inside root
Active transport of ions/solutes into roots «enabling osmosis»
Deep/wide ranging/extensive root systems/taproots/many root hairs
Thick/waxy cuticle reduces transpiration/water loss/evaporation
Small/no leaves/reduced surface area of leaves/thorns instead of leaves
Few stomata/stomata in pits/rolled leaves
Hairs on leaf surface «to reduce air flow near the leaf/reflect sunlight»
Stomata open at night/CAM physiology to reduce water loss
Explain the processes by which minerals are absorbed from the soil into the roots.
plants absorb minerals in ionic form/mineral ions;
nitrate / phosphate / potassium / other example of mineral;
minerals can be absorbed by (facilitated) diffusion;
(diffusion is) movement of ions from high to low concentration/down concentration gradient;
root hair cells provide a large surface area for absorption;
fungal hyphae help to absorb minerals/phosphate;
minerals absorbed by active transport;
as mineral ion concentration is smaller outside the root than inside / absorbed against a
concentration gradient;
active transport requires energy/ATP;
occurs through pump/carrier proteins;
proton pump transports hydrogen ions/H+ out of cell (allowing mineral movement in);
water enters roots through the root hairs by osmosis;
root hairs provide an extended surface area (for active transport and osmosis);
active transport of ions from soil into the roots (enhances osmotic pressure);
osmotic pressure moves water into the xylem;
water is carried (in a transpiration stream) in the xylem;
adhesion of water to the inside of the xylem helps move water up;
cohesion of water to itself enhances water movement up the xylem;
water diffuses into air spaces (in spongy mesophyll) of leaves;
it passes out through the stomata by evaporation/transpiration;
evaporation sets up a transpiration pull that keeps the water moving;
guard cells control the rate of transpiration pull/evaporation;
xylem vessels are tubes with helical rings to enhance water movement/resist low pressure;
Photosynthesis and transpiration occur in leaves. Explain how temperature affects these
processes.
photosynthesis rate increases as temperature rises (up to an optimum temperature);
(due to) increase in the rate of enzyme catalysed reactions/light independent reactions/the Calvin
cycle;
(steep) drop in rate of photosynthesis above the optimum;
at high temperatures enzymes/Rubisco/RuBP carboxylase denature(s);
graph with correctly labelled axes showing relationship between temperature and rate of
photosynthesis;
transpiration rate increases as temperature rises;
(energy/heat leads to more) to more evaporation of water (in the leaf);
faster diffusion of water vapour at higher temperatures;
relative humidity falls as temperature rises / warmer air can hold more water vapour;
stomata may close at very high temperatures reducing the transpiration rate;
some plants open their stomata at very high temperatures to cool by transpiration;
Describe how plants carry out gas exchange in the leaves.
gases/O2 and CO2 enter/exit the leaf through the stomata;
by diffusion / down the concentration gradient;
photosynthesis maintains concentration gradients/high O2 and low CO2 in the leaf;
guard cells open the stomata during the day / close the stomata at night;
gases/O2/CO2 move through air spaces in the spongy (mesophyll);
CO2 dissolves in moisture in (mesophyll) cell walls;
Explain how minerals move into plants.
a. minerals bound to soil particles;
b. examples of three nutrients from: phosphate, nitrate, magnesium, iron, calcium, potassium,
sodium, magnesium;
c. minerals dissolve in water;
d. mass flow causes movement of minerals with movement of water through soil;
e. minerals diffuse down a concentration gradient towards roots (as the mineral concentration
next to the roots is continuously decreasing);
f. minerals enter the plant through roots;
g. by active transport / use of ATP;
h. branching of roots increases surface area for absorption of minerals;
i. root hairs increase surface area (for the absorption of minerals);
j. hypha of (mutualistic) fungi may enhance movement of selected ions into roots / increase
surface area;
k. root hairs have many mitochondria to provide energy/ATP for active transport;
l. export of H+ creates electrochemical gradient / displaces ions bound to soil/clay;
m. that causes positive mineral ions to diffuse into (root) cells;
n. negative mineral ions cross membrane linked to H+ ions moving down (H+) gradient;
Outline the conditions needed for the germination of a typical seed.
a. water to rehydrate the seed / activate metabolic processes;
b. oxygen for aerobic respiration as seed germinates;
c. suitable temperature for enzyme activity;
d. each type of seed has specific temperature requirements / temperature requirements ensure that
seeds germinate at the correct time of year;
Explain how abiotic factors affect the rate of transpiration in terrestrial plants.
(transpiration is) loss of water vapour from the leaves/stomata (and stems) of plants;
a. less transpiration/water loss as (atmospheric) humidity rises;
b. air spaces inside leaf are saturated/nearly saturated (with water vapour);
c. smaller concentration gradient with higher atmospheric humidity;
d. more transpiration/water loss as temperature rises/with more heat;
e. faster diffusion / more kinetic energy (of water molecules);
f. faster evaporation (due to more latent heat available);
g. more transpiration/water loss as wind (speed) increases;
h. humid air/water vapour blown away from the leaf;
i. increasing the concentration gradient (of water vapour);
j. more transpiration/water loss in the light;
k. light causes stomata to open / stomata closed in darkness;
high light (intensity)/sunlight (usually) increases photosynthesis/water evaporation through the
stomata/transpiration;
l. low CO2 concentration inside leaf in bright light so stomata open wider;
stomata open to allow gaseous exchange/entry of CO2;
abscisic acid stimulates closing of stomata;
guard cells open/close the stomata;
adaptations of (xerophyte) plant structures reduce water loss/transpiration;
one example;
(thicker leaf cuticle / reduced surface area/rolled leaves/spines / sunken/reduced stomata / close
stomata in day / low growth form / CAM / C4 physiology)
Explain the role of limiting factors in photosynthesis.
factor nearest its minimum/furthest from its optimum is limiting;
increasing a limiting factor with other factors constant increases the rate;
increasing a non-limiting factor with other factors constant has no effect on rate;
light intensity is limiting in dim/low intensity light / at night;
photosynthesis (directly) proportional to intensity up to plateau / graph to show this;
light intensity affects the light-dependent reactions/production of ATP/NADPH;
temperature limiting at low and high temperatures;
optimum temperature with lower rates above and below plateau / graph to show this;
low temperatures limit the rate of light-independent reactions/Calvin cycle;
RuBP carboxylase/rubisco does not fix carbon dioxide at high temperatures;
carbon dioxide concentration is limiting in bright light and warm temperatures;
photosynthesis is (directly) proportional to CO2 concentration up to plateau / graph to show this;
low CO2 concentration limits carbon fixation/reaction between CO2 and RuBP;
Angiospermophyta have vascular tissue (xylem and phloem) that bryophyta lack. Suggest
advantages that vascular tissue confers.
would make it easier to stand upright (against gravity)/structural support / allows
(angiospermophytes) to be bigger;
could put leaves higher in the air to get more sunlight;
transport of water supply/nutrients from roots to other tissues;
could (more efficiently) transport/translocate sugars/food from leaves for storage;
Outline how the glucose produced as a result of photosynthesis is transported and stored in
plants.
glucose transformed to sucrose;
translocation of sugars/sucrose;
by phloem;
active process / requires energy;
from source to sink;
source is photosynthetic tissue/leaves;
sink is fruits/seeds/roots/storage organs;
(sucrose) converted to starch;
stored in storage organs/roots/tubers;
Describe the transport of organic compounds in vascular plants.
a. phloem transports organic compounds/sucrose
b. from sources/leaves/where produced to sinks/roots/where used
c. through sieve tubes/columns of cells with sieve plates/perforated end walls
d. loading of organic compounds/sucrose into /H+ ions out of phloem/sieve tubes by active
transport/using ATP
e. high solute concentration causes water to enter by osmosis (at source)
f. high (hydrostatic) pressure causes flow (from source to sink)
g. companion cells help with loading / plasmodesmata provide a path between sieve tubes and
companion cell
h. translocation/mass flow
Outline active transport in phloem tissue.
a. active transport/pumps used to load sugars/sucrose into phloem/companion cells/sieve tubes
b. loading in sources/unloading in sinks
OR
sucrose/sugars moved from source to sink
c. active transport moves H+ out of phloem/sieve tubes «to make H+ gradient in the leaf/source»
d. H+ gradient used for co-transport of sucrose into phloem/sieve tubes/companion cells
Auxin is a protein. Explain its role in phototropism.
auxin is a plant hormone;
produced by the tip of the stem/shoot tip;
causes transport of hydrogen ions from cytoplasm to cell wall;
Changes the pH of the extracellular environment/cell wall
increases activity of proton pumps
decrease in pH / H+ pumping breaks bonds between cell wall fibres;
makes cell walls flexible/extensible/plastic/softens cell walls;
auxin makes cells enlarge/grow;
has effect on rate of mitosis
gene expression also altered by auxin to promote cell growth;
promotes transcription of some genes
(positive) phototropism is growth towards light;
shoot tip senses direction of (brightest) light;
auxin moved to side of stem with least light/darker side
causes cells on dark side to elongate/cells on dark side grow faster;
Outline the metabolic processes that occur in starchy seeds during germination.
a. water absorbed by the seed / seed rehydrated;
b. water activates metabolism;
c. gibberellin synthesized/produced/secreted;
d. gibberellin stimulates the production of amylase;
e. amylase digests/hydrolyses starch to maltose;
f. maltose converted/hydrolysed to glucose (by maltase);
g. glucose used in aerobic respiration;
h. glucose used in synthesis/production of cellulose;
Outline how and where energy is stored in plants.
a. glucose (from photosynthesis) stored as starch;
b. starch stored (as granules) in chloroplast/in plastids;
c. (starch stored) in seeds/storage roots/stem tubers;
d. stored as lipids/oils;
e. (lipid/oils storage) in seeds;
f. lipids store twice as much energy per gram as starch;
Outline pollination, fertilization and seed dispersal.
pollination is the transfer of pollen to the stigma/carpel/pistil of a flower;
pollen grains grow a pollen tube down the style to the ovule;
male and female gametes/nuclei join/fuse (in the ovule/ovary) during fertilization;
the ovary matures into a fruit;
dispersal of seeds depends on the fruit;
example of seed dispersal; (e.g. pods split open to scatter seeds, e.g. animal eats fruit / ingests
and egests seed)
Explain how flowering is controlled in long-day and short-day plants.
lowering affected by light;
phytochrome;
exists in two (interconvertible) forms/Pfr and Pr;
Pr (red absorbing/660 nm) converted to Pfr (far-red/730 nm absorbing) in red or day light;
sunlight contains more red than far red light so Pfr predominates during the day;
gradual reversion of Pfr to Pr occurs in darkness;
Pfr is active form / Pr is inactive form;
in long-day plants, flowering induced by dark periods shorter than a critical length / occurs when
day is longer than a critical length;
enough Pfr remains in long-day plants at end of short nights to stimulate flowering;
Pfr acts as promoter of flowering in long-day plants;
short-day plants induced to flower by dark periods longer than a critical length/days shorter than
a critical value;
at end of long nights enough Pfr has been converted to Pr to allow flowering to occur;
Pfr acts as inhibitor of flowering in short-day plants;
The flowers of angiospermophyta are used for sexual reproduction. Outline three processes
required for successful reproduction of angiospermophyta.
a. meiosis / production of male and female gametes
b. pollination / transfer of pollen from anther to stigma
c. fertilization happens after pollination / fertilisation is joining of gametes
d. seed dispersal / spread of seeds to new locations
I Sepal
II Ovary
III Petal
Phylum is Angiospermophyta
a. could be pollinated, confirms the hypothesis;
b. stigma/anther inside the flower/ring of petals so as visiting animal enters it brushes past them;
c. colourful petals (provide contrast) so that flowers can be seen by animals;
d. (slightly) cone-shaped flowers so animals come in;
State the term for a region of rapid cell division within a plant: «apical» meristem/shoot apex
Describe briefly how scientists obtained leaf phloem sap from the potato plants.
a. aphids insert stylet in «potato» plants/feed from «potato» plants
b. phloem exudates/sap obtained from severed stylets
II is Xylem
I is Phloem as it has a stylet embedded in it
Aphids insert their stylets into phloem
Is closer to the surface/exterior/outside the xylem
Cells smaller than xylem tissue «below it»
Smaller «companion» cells are adjacent to larger «sieve tube» cells
Explain how aphid stylets can be used to study the movement of solutes in plant tissues.
Aphids tap into phloem with their stylets «to use sap as a food source»
Plants grown in radioactive CO2/14CO2 incorporate it into carbohydrate
Phloem contents/sap/fluid flows through the stylet
Aphid body severed/cut from stylet «after stylet inserted into phloem»
Analyze «sap/fluid exuded from stylet» for solutes/carbohydrates
OR
Radioactive-labelled carbon can be detected «in the phloem sap»
Stylets at different parts of the plant can show sequence/rate of movement