Module Two
What are animals and plants built from?
feature
function
nucleus
controls cell
accept contains genetic material or genes or chromosomes or stores
information
do not credit the brain of the cell
cytoplasm
where respiration occurs
accept contains food or mitochondria
or reactions occurs
membrane
lets water or chemicals in and or out
accept surrounds the cell or lets some things in but not others
do not credit keeps things out or protection
mitochondria
where energy released
ribosomes
where protein synthesis
Cell Wall
Holds cell’s shape
Vacuole
stores cell sap
Chloroplast
contains chlorophyll which absorbs light energy
Specialised Cells
White Blood Cell
 fight or ingest or kill bacteria or germs or viruses or microbes
accept produce antitoxins or antibodies fight disease (organisms)
do not credit fungus
Red Blood Cell
 (transport) oxygen or carry haemoglobin
accept transport carbon dioxide or helps form scabs
Palisade Mesophyll Cell

has lots of chlorophyll/chloroplasts

to absorb light/produce food
Sperm

long tail

streamlined head
Module Two
Differences between Plant and Animal Cells
Plant cell
Animal cell
(has) vacuole or has cell sap
no vacuole or small /
temporary vacuole
or no cell sap
(has) wall/ cellulose
no wall / cellulose
or only membrane
(stores) starch or doesn’t store
glycogen
doesn’t store / have
starch
or stores glycogen
How do dissolved substances get into and out of cells?
Diffusion
 movement of particles
 from high concentration to low concentration
Dissolved substances move by diffusion transport.
Substances are sometimes absorbed against a concentration gradient. This requires the
use of energy from respiration. The process is called active transport. It enables cells to
absorb ions
from very dilute solutions. Other substances, such as sugar and ions, can also pass
through cell membranes.
• movement of molecules / ions
• from low to high concentration
• requires energy / respiration
Many organ systems are specialised for exchanging materials.
In humans:
− the surface area of the lungs is increased by the alveoli
− and that of the small intestine by villi.
The lungs are in the upper part of the body (thorax) protected by the ribcage and
separated from the lower part of the body (abdomen) by the diaphragm.
The breathing system takes air into and out of the body so that oxygen from the air can
diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into
the air.
The alveoli provide a very large, moist surface, richly supplied with blood capillaries so
that gases can readily diffuse into and out of the blood.
Module Two
The villi provide a large surface area with an extensive network of capillaries to absorb
the products of digestion by diffusion and active transport.
In plants:
– carbon dioxide enters leaf cells by diffusion
– most of the water and mineral ions are absorbed by root hair cells.
The surface area of the roots is increased by root hairs and the surface area of leaves by
the flattened shape and internal air spaces.
Plants have stomata to obtain carbon dioxide from the atmosphere.
Plants lose water vapour from the surface of their leaves. This loss of water vapour is
called transpiration. Transpiration is more rapid in hot, dry and windy conditions. Most
of the transpiration is through stomata. The size of stomata is controlled by guard cells
which surround them. If plants lose water faster than it is replaced by the roots, the
stomata can close to prevent wilting.
How do plants obtain the food they need to live and grow?
Adaptations of leaf:
 flat surface
 stomata
 thin
 chloroplasts
 veins
 large surface area
 air spaces
Leaf:

chlorophyll is green
e.g. green areas have chlorophyll

chlorophyll/green is needed for photosynthesis
e.g. it is only in green areas that photosynthesis can take place

light is needed
e.g. it does not happen in the dark do not accept sunshine/sun

photosynthesis produces/makes starch
Module Two
Factors affecting rate of Photosynthesis






(presence of) chlorophyll or (amount of) chloroplasts
accept green leaves (or other green parts)
(sufficient) light (intensity)
(light) of a suitable wavelength
Temperature (enzyme action)
Concentration of CO2
Availability of water
Factors in Greenhouse that can maximise output
 provide (more) light
 provide (more) CO2
 provide (plenty of) water
 increase temperature
 if any one of these is low it will limit the reaction
Photosynthesis is summarised by the equation:
Uses of glucose:





stored as fructose
stored as sucrose
stored as starch
stored as oil or lipid
moved or transported away in the phloem
do not accept “stored” by itself





respired or burnt up for energy or fuel changed to protein
changed to cellulose
changed to fructose
changed to starch
changed to oil or lipid
Nitrate
 produces amino acids which are then used to form proteins
 stunted growth if nitrate ions are deficient
Magnesium
 needed for chlorophyll production.
 yellow leaves if magnesium ions are deficient.
Module Two
What are enzymes and what are some of their functions?
What is an enzyme
 biological catalyst
accept protein catalyst
What do they do?

speed up reactions

bring about reactions at lower temperatures

lower pressures

less expensive process
How do they work?
 particles / they gain energy
 particles / they move faster
 accept move more violently
ignore vibrate faster or start to move
only or more active
do not accept move more
 collide more often or more collisions or more chance of collision
 have more energy when they collide or more energetic collisions or more
collisions with activation energy
 accept more successful / fruitful / violent / forceful collisions
accept more likely to react
Why do they stop working?

does not work above the optimum temperature or denatured / damaged / destroyed
or only works best at an optimum temperature
some indication of optimum temperature
do not accept killed / do not work
accept only work over a narrow pH range
ignore deactivated or decreases activity or explanations about cost
or not removed with product
Why is digestion needed?

Food molecules (too) large or insoluble
do not accept “breaking up”
Module Two
do not accept complex
accept ‘need to make molecules
smaller / soluble’ – reverse argument

cannot be absorbed or cannot enter blood or cannot pass through wall /
lining of intestine / gut or villi
“body” not enough
not large intestine
Carbohydrate Digestion





digested / broken down / made soluble
by carbohydrase / amylase / enzyme
in mouth / in small intestine / from salivary galnds / from pancreas
into glucose
glucose/smaller molecules/products of digestion absorbed into blood
Protein Digestion





digested / broken down / made soluble
by protease / enzyme
in stomach / in small intestine / from stomach / from pancreas
into amino acids
amino acids/smaller molecules/products of digestion absorbed into blood
Lipid Digestion







works best in neutral / alkaline conditions
digested / broken down / made soluble
by lipase / enzyme
in small intestine / from pancreas
bile emulsifies fats (see below)
into fatty acids and glycerol
fatty acids and glycerol/smaller molecules/products of digestion absorbed
into lacteal duct
Role of Bile
•
neutralises acid / makes conditions alkaline / raises pH
•
enzymes (in small intestine) work (more/most effectively) or
stop/prevents enzymes being denatured
•
emulsifies fats/lipids or description of emulsification
do not accept breakdown unqualified
•
larger surface area
Module Two
Biological detergents
 protein-digesting enzymes (proteases)
 fat-digesting enzymes (lipases).
Benefits of biological detergents
•
less heat / energy / electricity / power required /used /
wasted
ignore lower temperature
•
conserves fuel supplies or less fuel used
•
less pollution from power stations / owtte
accept less global warming
or
less CO2 / carbon emissions / greenhouse gases
or
less SO2 / acid rain
NB only direct effects
less pollution only is not enough
In industry:
proteases
 pre-digest. the protein in some baby foods
carbohydrases
 convert starch into sugar syrup
isomerase
 convert glucose syrup into fructose syrup
 much sweeter
 used in smaller quantities in slimming foods.
Respiration

in mitochondria

glucose decomposes / breaks down / reacts
Module Two

CO2 + water

(quick) source of energy
Equation:
dioxide + water (+ energy)
Energy used to:
 build up larger molecules using smaller ones
 enable muscles to contract
 maintain a steady body temperature in colder surroundings
 build up sugars, nitrates and other nutrients into amino acids
 which are then built up into proteins.
The energy that is released during respiration is used to enable muscles to contract.
Effect of exercise:
− the heart rate increases
− rate and depth of breathing increases
− the arteries supplying the muscles dilate.
•
•
•
•
•
•
•
•
•
•
increased blood (flow)
(more) oxygen supplied or aerobic respiration
(more) glucose / sugar / food supplied
(higher rate of) respiration
less anaerobic respiration
(more) energy needed / released
(more) carbon dioxide removed
(muscles) doing (more) work or muscles contracting
remove heat / cooling
remove lactic acid or less lactic acid formed
Effect of training:
• trained athlete has higher stroke volume / more blood per beat
• same volume blood expelled with fewer beats or for same heart rate more blood
is expelled
These changes increase the blood flow to the muscles and so increase the supply of
sugar and oxygen and increase the rate of removal of carbon dioxide.
Glycogen stores in the muscle are used during exercise.
Module Two
If muscles are subjected to long periods of vigorous activity they become fatigued, ie
they stop contracting efficiently. If insufficient oxygen is reaching the muscles they use
anaerobic
respiration to obtain energy.
• increased aerobic respiration or decreased anaerobic respiration
• increased energy supply / need less lactic acid formed or to breakdown lactic acid
or less O2-debt
• can do more work or can work harder / faster / longer or less fatigue / cramp /
pain
Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid.
As the breakdown of glucose is incomplete, much less energy is released than during
aerobic respiration.
Anaerobic respiration results in an oxygen debt that has to be repaid in order to oxidise
lactic acid to carbon dioxide and water.
• longer rest period enables (more) oxygen content (of muscles) to be replenished
• enables (more) aerobic respiration or less / no anaerobic respiration
• enables breakdown / removal of lactic acid or oxygen debt paid off
Which human characteristics show a simple pattern of inheritance?
Why Mendel’s work was not accepted:
•
other scientists not aware of his work
•
chromosomes / DNA / genes not seen / discovered / known
do not accept there was no interest in genetics
•
other theories accepted at the time
•
not considered to be a scientist / not eminent / respected
Module Two
DNA
(gene) in DNA (i.e. mention of DNA)
(DNA) contains bases
(bases) code for amino acids (in protein)
(amino acids) in correct order
to make the protein
Body cells
 chromosomes in pairs.
 divide by mitosis
 during growth or to produce replacement cells.
Mitosis
 molecule has two long strands/double helix;
 idea of held together by (weak) bonds;
 each strand has 4 different types of base;
)
 which pair with specific bases in opposite strand; )
 when strands separate;
) OWTTE
 each strand acts as a ‘complementary’ template; )
 makes 2 identical strands
Sex cells (gametes)
 Only one chromosome from each pair
 Formed by meiosis
 Introduces variation
Gamete formation:
 chromosomes are copied
 cell divides twice to form four gametes,
 each with a single set of chromosomes.
Mitosis v Meiosis
meiosis
mitosis
sexual
asexual
gametes
growth
ovary or testes
or gonads
all other cells
Module Two
half number
of chromsomes
same number
of chromosomes
haploid or
23 chromosomes
diploid or
46 chromosomes
reassortment or
variation possible
or not identical
no reassortment
or no variation
or identical
4 cells produced
2 divisions
2 cells produced
1 division
Zygote formation:
 gametes join at fertilisation,
 single body cell with new pairs of chromosomes formed.
 new individual develops
 cell repeatedly divides
 by mitosis.
Stem Cells:
 Undifferentiated/specialized cells
 Can be made to form any kind of cell
 Treatment with these cells may help conditions such as paralysis.
Human body cells
 23 pairs of chromosomes
 One pair carries sex chromosomes
 females the sex chromosomes are the same (XX)
 males the sex chromosomes are different (XY).
Dominant
an allele is dominant if it is expressed in the heterozygous phenotype
Recessive
a recessive allele is not expressed in the presence of its contrasting allele
do not accept powerful
do not accept stronger
Allele
different forms of a gene controlling a characteristic and occupying the same site
on homologous chromosomes
Module Two
Gene
unit of DNA/sites on chromosomes carrying the information that determines
characteristics
Some disorders are inherited:
Polydactyl
 extra finger/toe
 dominant allele of a gene
 passed on by only one parent who has the disorder
Cystic fibrosis
 disorder of cell membranes
 inherited from both parents
 parents are carriers of the disorder without actually having the disorder
 recessive allele
Embryos can be screened for the alleles that cause these and other genetic disorders.
For cystic fibrosis
pros:
•
reduce number of people with cystic fibrosis (in population)
•
reduce health-care costs
•
allows decision / emotional argument,
eg allows people to make choices about termination
cons:
•
possible damage / risk to embryo / fetus / baby
•
possible harm / risk to mother
•
(may) have to make ethical / moral / religious decisions
for polydactyly:
•
cures ‘disfigurement’
•
but condition not life threatening
•
so risks to foetus / mother unjustified
Module Two
Stem Cells
Advantages:
 Stem cells can grow into many different kinds of body cells.
 Large numbers of stem cells can be grown in the laboratory.
 Stem cells may be used to treat some human diseases.
 No need to take anti-rejection drugs for rest of life
 Reduces effect of shortage of donors
Disadvantages:
 Stem cells may grow out of control. (causes tumours)
 Collecting and growing stem cells is expensive.
Natural Selection
 natural variation exists in a population;
 due to mutation
 some alleles are an advantage;
 (give specific reason why)
 such animals more likely to survive;
 and pass these alleles/ genes onto succeeding generations
Problems with fossils


there is a lack of valid / reliable evidence
because the early organisms were soft bodied or because remains were
destroyed by geological action
Speciation
 populations become isolated / separated
 by areas between mountains/river
 there was genetic variation in these isolated communities
 natural selection acted differently on these isolated communities eventually
resulting in interbreeding being no longer possible and so
new species have been formed

Causes of extinction
•
changes to the environment / named changes
•
new competitors
•
new diseases
•
new predators
•
volcanic eruptions
•
collisions with asteroids