VCE Biology
TSFX REVISION LECTURE
UNIT 3 Part 1
Veronica Parsons 2015
Cells
Biochemistry
Biomolecules
Area of Study 1
Unit 3: Signatures of Life
Immune System
Coordination & Regulation
Area of Study 2
v
Pathogens
Revision‐What Can you Do?
• Lecture today-Listen!
• Past VCAA Exams from
Website Going
Backwards from 2014
including Sample. Keep
Notebook Close by
divided into 4 sections for
each area of Study-write
down theory from
questions you are getting
wrong
• Read over TSFX notes with
highlighter regularly.
• Study Groups-Make
Kahoots
• Teach someone!
Exam Horror Stories
Exam Horror Stories
Exam Horror Stories
2014 Exam Horror Stories
Exam Horror Stories
Drawing or Labelling a Plasma Membrane
A
B
C
D
Exam Horror Stories
What to Learn from these Horrors???
•
•
•
•
•
•
•
•
•
Avoid one word answers for one
mark questions
Use the word ‘whereas’ in
comparative statements
Use the word ‘so’ twice in an
explain question.
Draw simple, big, clearly labeled
diagrams
Use data to support your answers
Read questions very carefullylook for distractors!
One dot point per mark + one for
luck
Ask yourself..”what is the
intention of the question”
Be positive-use the exam as an
opportunity to show them how
much you know and how hard
you have worked.
Practice Exam Question
Which of the following combination of
polysaccharides and function is correct:
a.
b.
c.
d.
Read each word very carefully!
Chitin: Structural component of cell membranes.
Cellulose: Energy store
Starch: structural component of plant cell walls
Glycogen: Store of energy.
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If a cell could talk???
 I exist in this watery world because I have an insoluble selectively permeable membrane
 I need to receive inputs, remove wastes & export products
 I need to make essential biomacromolecules (by condensation)
 You think you have a management problem! (talking about biology teachers). I need to control & regulate a host of simultaneous reactions that are energy dependent. Provide a constant supply of reactants and export a constant supply of products.
 I need to know everything. I need to receive signals and respond.
 I need to divide, copy accurately and pass on my information manual to my daughter cells.
 Most of the time I get it right, but sometimes things go wrong.
https://www.youtube.com/watch?v=oqGuJhOeMek
The cell is a bag of molecules
Pg 15 Water‐a unique molecule
•
Water is the most abundant compound in our
bodies
•
Water is the most common solvent (dissolves solid,
liquid, or gaseous solutes, resulting in a solution) in
everyday life.
•
Substances that dissolve readily in water are
called hydrophilic or polar.
“Like dissolves Like”
“Polar dissolves Polar”
“Non Polar dissolves Non Polar”
Pg 18 Biological Hierarchy
Pg 18 Organic vs
Inorganic
organic means that a molecule has a carbon backbone, with some hydrogens
thrown in for good measure. Living creatures are made of various kinds of organic compounds. Eg: Carbohydrates, Lipids,Proteins, Nucleic Acids, Coenzymes eg ATP
Inorganic molecules are composed of other elements. They can contain hydrogen or carbon, but if they have both, they are organic.Eg, H2O, CO2, O2, Cofactors
Pg 19 Organic Molecules
Organic Molecule
Elements
Monomer or Subunit
Polymer or
larger unit
Carbohydrate
C H O
Monosacchari
de
Glucose, Ribose
Polysaccharide Eg Starch, s
Glycogen, Cellulose, Chitin
ProteiNS
C H O N (S)
Amino Acid (20)
Polypeptides
Proteins
Lipid
C H O (P) Fatty Acid
Nucleic Acid
CHONP
Nucleotide
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Examples
Enzymes, Hormones, Antibodies
Neurotransmit
ters
Phospholipids, Cholesterol. Tryglycerides.
Hormones
Nucleic Acids
DNA, mtDNA, tRANA, rRNA, mRNA
Diagrammatic Representations of Molecules
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VCAA 2006
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Pg 20 Synthesis of biomacromolecules
through the Condensation Reaction
•
Making Polymers is Wet Work!
•
Condensation (water releasing) makes bonds.
•
Loss of OH from one monomer and H from another results in overall loss of one water molecule in forming the bond
•
Anabolic‐building up reactions eg protein synthesis
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FAQ’s
• Students are expected to
recognise diagrammatic
representations of
glucose, identify glucose
as a monomer of
polysaccharides and
other carbohydrates, and
understand the
mechanism of the
condensation reaction
(that is, a water molecule
is lost when a monomer is
added to another
monomer or a
polysaccharide
structure).
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Pg 21 Glucose
Glucose is created in the process of photosynthesis and
is used in the process of cellular respiration.
Polysaccharides
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Pg 26 FAQ’s
•
For lipids, students are
expected to recognise
diagrammatic
representations of fats
(triglycerides) and
phospholipids, and identify
the role of phospholipids in
the cell membrane.
Students should understand
that the formation of
triglycerides involves
condensation reactions.
Although the role of
cholesterol in the plasma
membrane should be
understood, the specific
chemical structure of
cholesterol is not required.
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Lipids
Triglycerides
•
•
•
•
Fats & Oils-saturated fats &
unsaturated fats
Triglycerides have three fatty
acid molecules attached to a
single glycerol molecule.
Formation involves
Condensation Reactions.
Functions include
o
o
o
insulation layers which resist heat loss or gain
Energy storage
Buoyancy for aquatic animals.
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Phospholipids
Structural backbone of membranes.
Phospholipids have two
fatty acids attached to a
glycerol.
Pg 26‐Functions of Lipids‐
SHIP
Function of Lipids
• Lipids can serve many
functions within the cell,
including:
• Storage of energy for longterm use (e.g. triglycerides)
• Hormonal roles (e.g. steroids
such as estrogen and
testosterone)
• Insulation (retention of
thermal energy)
• Protection of internal organs
(e.g. triglycerides and waxes)
• Structural components (e.g.
phospholipids, cholesterol)
•
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Pg 31 Phospholipids
•
•
•
•
Consists of a phosphate group
(hydrophillic) and 2 fatty acid
tails (hydrophobic).
Within a membrane, the
phosphate faces aqueous areas
both inside cell (cytosol) and
outside cell (extracellular fluid).
The fatty acid tails are buried in
the middle.
The hydrophobic nature of the
tails ensure that only lipid soluble
(lipophillic, hydrophobic) or non
polar substances (eg steroid
hormones, alcohol, chloroform
etc) can directly diffuse through
cell membranes.
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Role of lipids in the plasma membrane
• Lipids move laterally and
can change place in the
one layer =dynamic
nature
• Can fuse with vesicles for
endocytosis and
exocytosis.
• Kinks in Fatty Acid tails
enhance fluidity
• Cholesterol reduces
fluidity by reducing
phospholipid movement.
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Pg 35 FAQ’s
•
Students are expected to understand that polypeptides and proteins are polymers of amino acids, formed
through condensation reactions. They are also expected to understand that the primary structure of a
polypeptide or protein is the sequence of amino acids that form the polypeptide or protein, and that the way
that polypeptides and proteins are folded, coiled or pleated can be described by secondary (within the chain)
and tertiary (overall chain shape) structures, and that those proteins made up of two or more polypeptide chains
may be described by a quaternary structure. Students are expected to identify α-helices and β-pleated sheets as
being the most common secondary structures. They are expected to understand that the shape of a protein
determines its properties and that protein denaturation through changes in temperature, changes in pH or
reaction with various chemicals may lead to a loss of biological function. Classifications of, and differences
between, different types of proteins such as globular and fibrous proteins are not required.
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Pg 35 Amino Acids
An amino acid is a relatively small molecule with characteristic groups of
atoms that determine its chemical behaviour.
The structural formula of an amino acid is shown at the end of the animation
below. The R group is the only part that differs between the 20 amino acids.
Phenylalanine
Cysteine
Alanine
Glycine
Valine
Amino
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H3H
C
H N
H
S
H H
CH
3
C
H H
R
C C O H
H O
Acid
Pg 38‐40 Levels of Protein Structure
•
4 different levels of organization:
•
Primary Structure: The order of amino acids
in the molecule.
•
Secondary Structure (within the chain)Local
3D folding structure formed by hydrogen
bonds.
•
Tertiary Structure: T(overall chain shape) he
total folding of the protein, held together
by hydrogen or ionic bonds.
•
Quaternary Structure: Is a structure
consisting of two or more polypeptide
chains.
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Pg 42 Functions of Proteins (HITSME)
•
•
•
•
•
•
•
•
•
Proteins are very diverse and serve a
number of different roles within the cell,
including:
Structure: Support for body tissue (e.g.
collagen, elastin, keratin)
Hormones: Regulation of blood glucose
(e.g. insulin, glucagon)
Immunity: Bind antigens (e.g. antibodies /
immunoglobulins)
Transport: Oxygen transport (e.g.
haemoglobin, myoglobin)
Movement: Muscle contraction (e.g. actin /
myosin, troponin / tropomyosin)
Enzymes: Speeding up metabolic reactions
(e.g. catalase, lipase, pepsin)
Amino acids can be joined together in a
condensation reaction to form a dipeptide
and water
This results in the formation of a peptide
bond, and for this reason long chains of
covalently bonded amino acids are called
polypeptides
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Pg 42How does Structure relates to Protein Function
Protein
Structure
Function
Enzymes
Specifically shaped active site that is complementary to a specific substrate Catalyse chemical reactions
Channel Proteins
Specific shape that allows a particular chemical (often hydrophilic) to move through
Transport
Receptors
Initiate signal Specific shape that transduction
allows a specific signalling molecule to bind which will lead to a cellular response
Antibodies
Y shaped molecule with 2 complementary antigen binding
Deactivate a pathogen
Hormones
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Specific shape that is complementary to a Initiate cellular response
Pg 43 Nucleic Acids(Polynucleotides)
There are two kinds of nucleic acid:
•
deoxyribonucleic acid (DNA) is
located in chromosomes in the
nucleus of eukaryotic cells and in
cytosol of prokaryotic cells.
•
It it also found in the
mitochondria and chloroplasts
•
ribonucleic acid (RNA) –there
are 3 types-ribosomal, messenger
and transfer.
•
Nucleic Acids are mostly
information storage molecules.
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FAQ’s
• Students are expected
to recognise the
monomers of DNA and
RNA and identify
complementary base
pairs.
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Monomer of a Nucleotide
• Nucleotides are the
building blocks of DNA
&RNA and contain a
phosphate component
(not phosphorus), a 5carbon sugar
component (not sugar)
and a nitrogenous
base component (not
base).
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DNA Template Strand
• The DNA Strand has the
sequence
5’ A-G-C-T 3’
What is the
complementary mRNA
strand
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Pg 48 DNA vs RNA Summary
DNA
RNA
No. of Nucleotide Strands
2
1
Sugar
Deoxyribose
Ribose
Bases
Adenine
Cytosine
Guanine
Thymine
Adenine
Cytosine
Guanin
Uracil
Functional Location
Nucleus (Eukaryotes)
Nucleus & Ribosome Cytoplasm (Prokaryotes) (Eukaryote)
Cytoplasm & Ribosome (prokaryote)
Do task pg 49 +pg 50
Stop Codons: UGA UAA UAG
Pg 57 Proteomics
•
•
An emerging branch of biology
which revolves around the
structure and function of
proteins. This involves a thorough
study of the proteome ( all
proteins expressed within a cell
for the duration of the life of the
cell) and is very closely related
to the study of the genome ( the
entire DNA content of the cell).
The genome carries genes
(sections of DNA) that provide
the blueprint for protein synthesis.
Certain sections of the DNA are
transcribed into RNA and then
translated into a protein within
the cell so that the specific
function of the cell can occur.
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Why did the phospholipid scream?
• …because it saw the
cytoskeleton
The Cell Theory pg 61
• All living things are
composed of cells and/or
their products
• All cells come from preexisting cells.
• The cell is the basic unit
of life.
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Pg 82 STRUCTURE =FUNCTION
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Cell Ultrastructures‐
Structures  Function
•
•
•
•
•
the role played by organelles
in the export of proteins
Ribosomes- Free (intracellular
protein synthesis)
Rough endoplasmic
reticulum- Transport of
extracellular proteins
Golgi apparatus –packaging
of extracellular proteins into
vesicles
Mitochondria-ATP for
endocytosis, Active transport
or exocytosis
Absorptive Cell Kidney
•
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Endocrine Pancreatic Cell
End of Part 1
Enjoy a 10 minute break!
the structure and function of the plasma membrane and the movement of substances across it:
– the fluid‐mosaic model of a plasma membrane
– the packaging, transport, import and export of biomacromolecules (specifically proteins)
– the role played by organelles including ribosomes, endoplasmic reticulum, Golgi apparatus and associated vesicles in the export of proteins
• Veronica Parsons 2014
Pg 89 Fluid Mosaic Model of Plasma Membrane
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VCAA 2006 EXAM
VCAA 2012
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VCAA 2012
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VCAA 2011 (2 Marks)
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Answer
Veronica Parsons 2013
FAQ’s
•
Diffusion, osmosis, active transport,
facilitated diffusion, endocytosis and
exocytosis are required in Unit 3.
Although simple diffusion, active
transport and facilitated diffusion are
introduced in Unit 1, they are also
relevant in Unit 3, in particular with
respect to protein transport,
movement of neurotransmitters
across a synapse and the movement
of other substances important in
cellular processes such as
photosynthesis and cellular
respiration. Exocytosis and
endocytosis are also important in
both Units 3 and 4 as they are
relevant to events including the
release of signalling molecules,
secretion of antibodies from plasma
cells and the phagocyticity of
macrophages and neutrophils.
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Movement Across Plasma Membrane
• Diffusion
• Osmosis
• Facilitated
Diffusion
• Active
Transport
• Vesicular
Transport
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Pg 92 Movement Across the Plasma Membrane
Osmosis
•
Osmosis is the passive movement of water molecules from a regions of lower solute concentration to a region of higher solute concentration across a partially permeable membrane until equilibrium is reached.
•
Passive (does not require energy).
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Osmosis
Pg 94 Osmosis in Animal and Plant Cells
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Porins
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Plasma Membrane
Movement Across the Plasma Membrane
Active Transport
•
DOES require energy
•
Movement of substances is AGAINST THE CONCENTRATION GRADIENT:
from low  high concentration
•
This type of transport will only occur in the presence of ATP
•
eg. Na+/K+ Pump Veronica Parsons 2014
Active Transport
Movement Across the Plasma Membrane
Vesicular Transport
•
Vesicular transport is transport of substances that requires the use of a vesicle
•
It requires ENERGY
•
Vesicles are used to transport substances both within the cell (intracellular) and out of the cell (extracellular)
•
Possible because: 1)
Membrane has some fluidity
2)
Small amounts can be added or removed without tearing the membrane (endo‐ & exo‐ cytosis)
3)
Membranes of all organisms are the same
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Vesicular Transport
Exam Question
• How does a monosaccharide enter an epithelial
cell?
Acceptable Answers
Facilitated Diffusion
Active Transport
Protein Channels
Protein Carrier Molecules
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• the nature of biochemical processes within cells:
– catabolic and anabolic reactions in terms of reactions that release or require energy
– the role of enzymes as protein catalysts, their mode of action and the inhibition of the action of enzymes both naturally and by rational drug design
– the role of ATP and ADP in energy transformation
– requirements for photosynthesis – excluding differences between CAM, C3 and C4 plants
– including: the structure and function of the chloroplast; the main inputs and outputs of the light dependent and light independent stages
– requirements for aerobic and anaerobic cellular respiration: the location, and main inputs and outputs, of glycolysis; the structure of the mitochondrion and its function in aerobic cellular respiration including main inputs and outputs of the Krebs Cycle and the electron transport chain
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Book 2 Pg 3 CATS EX SPIRE
• Catabolic Processes
are Exergonic
(breakdown)
• Example Cellular
Respiration
• Hydrolysis reactions are
also catabolic.
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Role of ATP & ADP in Energy Transformations
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Enzymes
•
•
•
•
Enzymes are large protein molecules
responsible for the thousands of
metabolic processes that sustain life.
They are highly selective catalysts,
greatly accelerating both the rate
and specificity of metabolic
reactions, from the digestion of food
to the synthesis of DNA
Like all catalysts, enzymes work by
lowering the activation energy for a
reaction, thus dramatically increasing
the rate of the reaction.
As a result, products are formed faster
and reactions reach their equilibrium
state more rapidly.
Enzymes are not consumed by the
reactions they catalyze, nor do they
alter the equilibrium of these
reactions. However, enzymes do
differ from most other catalysts in that
they are highly specific for their
substrates.
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Pg 5‐ Enzymes Lower Activation Energy
Activation Energy
Q9 p 16
MOVIE
Pg 8 Competitive Inhibition
•
•
•
Similar shape to substrate so
compete for the active site
& prevent the formation of
Enzyme-Substrate Complex
They fit into the Active Site,
but remain unreacted since
they have a different
structure to the substrate but
less substrate molecules can
bind to the enzymes so the
reaction rate is decreased.
Competitive Inhibition is
usually temporary, and the
Inhibitor eventually leaves
the enzyme.
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Non Competitive Inhibition
•
Prevent formation of Enzyme-Product
Complexes. So they prevent the substrate
from reacting to form product.
•
Usually, Non-competitive Inhibitors bind to a
site other than the Active Site, called an
Allosteric Site.
•
Doing so distorts the 3D Tertiary structure of
the enzyme, such that it can no longer
catalyse a reaction.
•
Many Non-competitive Inhibitors are
Veronica
Parsons
irreversible
and2014
permanent, and denature the
Rational Drug Design
• A focussed approach
using information about
structure of a drug
receptor or it’s ligand
to identify or create
candidate drugs.
• *Ligand-substances
that are able to bind to
a biomolecule such as
substrates, inhibitors,
neurotransmitters
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Relenza
Veronica Parsons 2015
End of Part 2
Enjoy a 20 minute break
2011 Question
2011 Answer
The Chloroplast
The chloroplast is enclosed by an
envelope consisting of two
membranes separated by a very
narrow intermembrane space.
Membranes also divide the interior
of the chloroplast
Thylakoid
membranes
into compartments:
flattened sacs called thylakoids,
which in places are stacked into
structures called grana.
Grana, are stacks of
thylakoid membranes
containing chlorophyll
Stroma, the liquid
interior of the
chloroplast
Inner
membrane
the stroma (fluid) outside
the thylakoids.
They contain DNA and also
ribosomes, which are used to
synthesize some of the proteins
within the chloroplast.
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Thylakoid
sac (disc)
Outer
membrane
Light Dependant Phase
• INPUTS: Light,
ADP +Pi
12H2O (Water),
NADP+,
• OUTPUTS: NADPH, 6O2,
ATP
• Inputs=LAWN
• Outputs= NOA
• *NADP= nicotinamide
adenine dinucleotide
phosphate
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Light Independent Phase
• INPUTS: CO2
•
ATP
•
NADPH
• OUTPUTS: 6H2O Water
•
ADP +Pi
•
NADP+
•
Gucose
• CAN WANG
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Biochemical Processes
Photosynthesis Stage
Light Dependent
Site
Eukaryote: Grana of Chloroplast
Prokaryote: Free Floating Chlorophyll
Inputs
Light
12 H2O
NADP+
ADP + Pi
Outputs
*
6O2
NADPH
ATP
Process





Light Independent
Eukaryote: Stroma of Chloroplast
Prokaryote: Cytosol
6CO2
NADPH
ATP
C6H12O6
6 H2O
NADP+
ADP +Pi



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Light energy absorbed by chlorophyll
Water molecules split to form H+
ions + O2 gas
O2 gas released via stomata
Excited electrons flow through an electron transport chain to provide energy for ATP synthesis
Unloaded electron acceptor molecules NADP+ accept H+ ions to form NADPH
In the Calvin Cycle, 6CO2 + H+ ions (from NADPH) used to synthesise sugars. This is called carbon fixation.
This is catalysed by tshe enzyme RuBisCO
Energy provided by the ATP produced in LD reaction.
GLYCOLYSIS (NAG NAP)
• INPUTS: NAD+
•
ADP +Pi
•
Glucose
• OUTPUTS: 2NADH
•
2ATP
•
2Pyruvate
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Anaerobic Respiration
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Anaerobic Respiration
Glycolysis
Cytosol
C6H12O6
2NAD+
4ADP + Pi
2 Pyruvate
2NADH +H ions
2ATP



Anaerobic (Fermentation)
(Plants&Yeast)
Cytosol
Pyruvate is further broken down into ethanol & CO2
Anaerobic
(Fermentation) (Animals)
Cytosol
Pyruvate is further broken down into Lactic acid & Water Veronica Parsons 2015
Glucose molecule is broken down to 2 pyruvate molecules
Hydrogen ions are removed from glucose and used to form loaded acceptor molecules NADH.
2 molecules of ATP are also produced
Aerobic Respiration
Stage
Glycolysis
Kreb’s Cycle (Citric Acid Cycle)
Site
Cytosol
Eukaryote: Matrix of Mitochondria
Prokaryote: Cytosol Inputs
Outputs
C6H12O6
2NAD+
4ADP + Pi
2 Pyruvate
2NADH +H ions
2ATP
2 Pyruvate
6NAD+
2FAD
2ADP + Pi
4CO2
6NADH +H ions
2FADH2
2ATP
Process







Electron Transport
Eukaryote: Cristae of Mitochondria
Prokaryote: Cytosol
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Oxygen
NADH +H ions
FADH2
32(34) ADP + Pi
6 H2O
NAD+
FAD
32(34)ATP

Glucose molecule is broken down to 2 pyruvate molecules
Hydrogen ions are removed from glucose and used to form loaded acceptor molecules NADH.
2 molecules of ATP are also produced
Pyruvate is converted to acetyl CoA and 1 Co2
molecule is released
Acetyl CoA enters Krebs Cycle and another 2 Co2 are released for each pyruvate.
The hydrogen ions are released from cycle and used to form NADH & FADH2
2 molecules ATP produced.
NADH & FADH2 come to cristae to transfer electrons from one cytochrome to another releasing ATP in the process. Oxygen is the final electron acceptor forming water
Krebs Cycle • INPUTS: NAD+
•
2 ADP+Pi
•
Pyruvate
•
FAD
• NAPS are FADS ?
• OUTPUTS: 6CO2
•
2ATP
•
NADH
•
FADH2
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Aerobic Respiration; Electron Transport
• INPUTS: O2
•
FADH2
•
32-34 ADP+Pi
•
NADH
• OUTPUTS: FAD
•
32-34 ATP
•
Water
•
NAD
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2010 Metabolism
Answer
VCAA 2006 EXAM
Summary Experimental Design
Year
Topic
Marks
Command Terms
2006
Designer Drugs
3
Design
2007
Enzymes
3
Outline Experiment
Explain Results
2008
Disease
5
State hypothesis
Outline Experiment
Describe Results
2009
Signalling Molecules 4
(Pheromones)
Outline Experiment
Describe Results
2010
Metabolism (Energy) 3
State hypothesis
Outline Experiment
Describe Results
2006 Experimental Design
• Design an experiment, using mice, to test the effectiveness of the (anti‐
viral) drug you have designed.
(3 Marks)
Examiner Report‐
Common Errors
•
Selecting only two mice without referring to repetition of the experiment;
•
Not mentioning the similarity of the mice and/or environment; •
Injecting mice with the virus and then waiting days or weeks before the drug was used; •
Administering the drug first and then exposing the mice to the virus days or weeks later; •
General statements about comparing the results, without any reference to what result would indicate effectiveness of the drug. •
Some Guys Prefer IndiViduals That Really Rock pg 10‐14
Sample‐eg Two large groups of identical members of the sample kept in the same environmental conditions . State a specific number (of reasonable magnitude) in each group, instead of simply describing a ‘large’ group or replication of the experiment.
Group_ Divide the sample into two groups of equal size‐One is the experimental Group and One is the Control Group.I
•
Independent Variable‐One of the groups then needed to receive no further treatment (the control group), the other group (the trial group) receives the drug under investigation •
Time after a few days, each of the groups needs to Examined ‐the number of mice that have developed the viral disease in each group counted.
•
Results‐ If the number of mice in the trial group is significantly less than the number in the control group, the drug has been effective. •
G
Sample
and
Allocate to 2 Groups (Experimental group
Control Group)
Pretest‐ infection of both groups with the virus against which the drug has been designed. •
S
Repeat‐experiment a number of times
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P
IV
T
Pretreatment
State the Independe4nt Variable
Time
R
Results
R
Repeat
2007 Experimental Design
A student predicted that if a temperature graph was prepared for carrot catalase activity, the optimal temperature would be expected to be much lower than that shown by catalase from humans. WHY????
Describe (or outline) an experiment you would carry out with pieces of carrot to test the accuracy of the prediction. Hydrogen peroxide is available as a 3% in water solution.
Explain fully what results would support or negate the student.s prediction.
(3 marks)
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Examiner’s Report
•
The use of at least two groups of identical pieces of carrot, placed at various temperatures (for example, 16°C and 37°C) in the same concentration of hydrogen peroxide. A specific number of carrot pieces could have been given (for example, 10). Students who mentioned the variable and other factors which were controlled adequately demonstrated their understanding of the experimental design and were awarded the first mark. •
For the second mark, students needed to discuss how catalase activity would have been measured. For example, collecting the gas to measure the production of oxygen gas, or observing the bubbles being produced. •
The third mark was awarded for a discussion of the expected results and a conclusion based on the student’s prediction. For example, more oxygen gas produced at 16°C compared to 37°C would support the prediction Veronica Parsons 2015
2008 Experimental Design
The human hormone vitamin D is found in high levels in some immunological tissues. A scientist predicted
that a defi ciency of vitamin D may play a role in the development of rheumatoid arthritis and hence treatment with vitamin D tablets may reduce development of the disease. The scientist decided to test this idea by using a strain of laboratory mice that normally developed rheumatoid arthritis.
Design an experiment to test the scientist’s prediction.
In your answer you should
state the hypothesis that you are testing
outline the experimental procedure that you follow
describe results that would support your hypothesis.
(5 Marks)
Veronica Parsons 2015
Examiner’s Report
Hypothesis That treatment with Vitamin D reduces the chance of mice developing rheumatoid arthritis Experimental Design Use two large groups (for example, 20) of similar mice which normally develop rheumatoid arthritis. Treat the experimental group with Vitamin D. The other group, the Control group, are given a placebo and do not receive Vitamin D. Keep all other factors constant, such as diet, space, water and temperature. Results For the hypothesis to be supported, fewer mice that are given Vitamin D should develop rheumatoid arthritis than those in the Control group. Veronica Parsons 2015
2009 Experimental Design
The beet caterpillar is an insect pest of the tomato plant. When a beet caterpillar starts to eat a tomato plant,
the plant responds by producing a chemical known as jasmonic acid. Jasmonic acid and its derivatives have a
variety of odours.
Some scientists have suggested that these odours attract wasps to the caterpillar‐affected plants.
i. Outline an experiment you would carry out to test this hypothesis.
ii. Describe the results that would support the hypothesis.
(4 marks)
Veronica Parsons 2015
Examiner’s Report
• Take two groups of tomato plants that are the same age type and state of health. One group is affected with beet caterpillars, the other is unaffected.
• Both groups are kept in the same environment (for example, the same temperature and water availability).
• Wasps are released and their activity is observed.
• Large numbers of plants are used or the experiment is repeated many times.
Veronica Parsons 2015
2010 Experimental Design
A pet food company has made two different types of food pellets, one hard and the other soft. Each kind of pellet has the same energy content. The company intends to test the pellets on a group of adult mice. You are provided with
• many adult mice. Each mouse is genetically identical and of the same weight
• two types of pellets, one hard and one soft. Outline an experiment that would allow you to determine if the hardness of the food pellets affects the balance between energy intake and energy expenditure.
In your answer you should
• state the hypothesis that you are testing
• outline the experimental procedure
• describe the results that would support or negate your hypothesis.
(3 Marks)
Veronica Parsons 2015
Examiner’s Report
• Hypothesis: That the mice fed hard pellets will weigh more than mice that are fed soft pellets
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Experimental procedure: Two groups of mice: one group fed hard pellets and the other soft, and all other variables controlled
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Results: Mice fed hard pellets weighed more than mice fed soft pellets
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Students did not need to state the features of the mice as these were given in the stem of the question; however, they needed to identify a factor which should have been controlled, for example, water availability.
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The results needed to relate directly to the hypothesis. Measuring weight was by far the most feasible method; however, measuring the activity of each group was also considered a suitable measure in this case.
Veronica Parsons 2015
Look for Patterns and Make Acronyms
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STARR (Sample-Treatment-All Factors Same-Results-Repeat)
RUDD(Rapid Burial-Undisturbed-Decomposer Free-Downward Pressure)
BADFEW(Biochemistry-Anatomy-Distribution-Fossils-Embryology-Witness)
IPMAT (Stages of Mitosis)
UGA UAA UAG (Stop Codons)
COD (Cross with homozygous Recessive-Observe Offspring-Decision)
VSSI (Variation-Struggle-Survival of Fittest-Inheritance)
VSSI with a B (Barrier)
GIFTS (Gene-Insert-From-Transform-Select)
Crocs Are Never Fine- (CO2-ATP-NADH-FADH2)
SHIP- (Storage-Hormones-Insulation-Protection-Structure)
HITSME ( Hormone-Structure-Immunity-Transport-Movement-Enzymes)
CATSEXSPIRE (Catabolic-Exergonic=Respiration)
PRIMATES
COAL (Complement Proteins-Chemotaxis, oponise, Agglutinate, Lysis)
Psychic Predictions
• Signal Transduction of
Lipid Based
(Hydrophobic)vs Protein
Based (Hydrophillic)
• Explain Active Transport
• Cell Mediated-T Cellsdraw one
• Explain how T Cells
protect against
pathogens or T cells
vaccination
• Transcription
• Autosomal Dominant
Pedigree
Veronica Parsons 2015
• Dihybrid test cross
linked vs unlinked
• Describe PCR
• Speciation
• GMO Mosquitos
• Tassie Devils-Founder
Effects
• Out of Africa vs
Multiregional.