Higher Biology Pupil Course Notes
Page 2 of 26 Duncanrig Secondary School CG 2015
At the end of this topic, you will be able to:
State that metabolism is all the sum total of all the enzyme controlled
chemical reactions occurring within a living cell.
State that anabolic pathways are synthesis reactions and require energy
input.
State that catabolic pathways are breakdown reactions and are energy
releasing.
State that metabolic pathways can have reversible and irreversible steps.
State that alternative routes can be taken to bypass steps in pathway.
State that membranes are a phospholipid bilayer with embedded and surface
proteins.
State that membranes form surfaces and compartments to localise metabolic
activity within the cell.
State that the folding of membranes and organelles increases the surface
area allowing high concentrations to accumulate and this can increase
reaction rates.
State that small compartments have a higher surface area to volume ratio
than larger compartments.
State that proteins in the membrane form pores, pumps and enzymes.
State that metabolic pathways are controlled by the presence or absence of
enzymes and the rate of activity of these key enzymes.
State that regulation of pathways can be controlled by intra and extra cellular
signal molecules.
State that the activity of enzymes depends on the depends on their shape,
and the ability of the substrate to bind to the active site.
Describe the induced fit model of enzyme action.
State that substrates have high affinity for the enzyme active site.
State that products have low affinity for the enzyme active site.
Describe the effect of enzymes on the activation energy.
Describe how the substrate and end product concentrations can affect the
direction and the rate of activity of the enzyme reaction.
State that metabolic reactions are reversible and the presence of a substrate
or removal of a product will drive a sequence of reactions in a particular
direction.
State that enzymes often act in groups or as multi enzyme complexes.
State that genes for some enzymes are continuously expressed.
Describe non competitive inhibition of enzyme action.
Describe competitive inhibition of enzyme action.
Describe how end product inhibition controls a metabolic pathway.
Higher Biology Pupil Course Notes
Page 3 of 26 Duncanrig Secondary School CG 2015
At the end of this topic you will have developed the following skills:
Demonstrating knowledge and understanding of biology by making
statements.
Describing information, providing explanations and integrating knowledge.
Applying knowledge of biology to new situations and analysing information.
Planning and designing experiments and practical investigations to test a
given hypothesis or to illustrate particular effects.
Carrying out experiments and practical investigations safely, recording
detailed observations and collecting data.
Selecting information from a variety of sources.
Presenting information appropriately in a variety of forms.
Processing information (using calculations and units, where appropriate).
Making predictions and generalisations from evidence or information.
Drawing valid conclusions and giving explanations supported by evidence or
justification.
Evaluating experiments and practical investigations and suggesting
improvements.
Communicating findings and information effectively.
Higher Biology Pupil Course Notes
Page 4 of 26 Duncanrig Secondary School CG 2015
Prior Learning: National 5 Biology
Unit 1 Cell Biology Sub Topic 2 Transport Across Cell
Membranes:
The cell membrane consists of phospholipid and protein molecules.
The cell membrane is selectively permeable.
Transport of materials across the membrane can be either passive or active.
Passive transport includes diffusion and osmosis and does not require energy.
Diffusion is the movement of molecules down a concentration gradient.
Active transport is the movement of molecules and ions against a concentration
gradient.
Active transport requires energy.
The energy for active transport comes from respiration.
Factors that affect the rate of respiration, will also affect the rate of active
transport.
Unit 1 Cell Biology Sub Topic 5 Proteins and Enzymes:
All proteins are made of chains of amino acid molecules.
The sequence of amino acids in a protein codes for and determines the protein’s
shape.
The shape of a protein determines it’s function.
Proteins provide a vital structural role in all cell membranes.
Enzymes function as biological catalysts because they speed up the rate of
all biochemical reactions in living organisms.
Enzymes are made inside living cells.
Although enzymes take part in a reaction they remain unchanged at the end of
it and can be used repeatedly.
The active site of an enzyme is the place on the enzyme's surface which
matches the shape of the substance that it works on (its substrate).
An enzyme is specific to its substrate and produces specific product(s),
working like a lock and a key.
Higher Biology Pupil Course Notes
Page 5 of 26 Duncanrig Secondary School CG 2015
Cell Metabolism
Metabolism is the sum total of all the enzyme controlled chemical reactions occurring
within a living cell.
There are two types of metabolic pathways:
Anabolic Pathways
Anabolic pathways are synthesis reactions and they require an input of energy.
Anabolic reaction (Energy In)
Catabolic Pathways:
Catabolic pathways are breakdown reactions and they release energy.
Catabolic reaction (Energy Out)
+ ENERGY
+ ENERGY
Higher Biology Pupil Course Notes
Page 6 of 26 Duncanrig Secondary School CG 2015
Summary of Metabolism
The diagram below that summarises catabolic and anabolic reactions in metabolism.
Add the following labels to the BOXES:
PROTEIN
ATP
ADP + Pi
GLUCOSE + OXYGEN
CARBON DIOXIDE+WATER
AMINO ACIDS
Add the following labels to the correct line:
CATABOLISM
ANABOLISM
ENERGY
TRANSFER
(aerobic respiration)
ENERGY ENERGY
Higher Biology Pupil Course Notes
Page 7 of 26 Duncanrig Secondary School CG 2015
Metabolic pathways consist of a series of enzyme controlled reactions. Each step in
this series of reactions may be reversible or irreversible allowing the process to
be kept under tight control. Metabolic pathways also contain alternative routes
where steps can be bypassed.
The diagram below shows the series of reactions involved in the breakdown of
glucose to pyruvate during glycolysis.
The conversion of intermediate 1 to intermediate 2 by enzyme B is reversible. If
more of intermediate 2 is formed than is needed, then it can be converted back into
intermediate 1 and used in the alternative pathway, for example, to build glycogen
in animal cells or starch in plant cells.
The conversion of intermediate 2 to intermediate 3 by enzyme C is irreversible and
is a key regulatory point in the pathway.
GLUCOSE
INTERMEDIATE
COMPOUND 1
INTERMEDIATE
COMPOUND 2
INTERMEDIATE
COMPOUND 3
PYRUVATE
GLYCOGEN (mammals)
STARCH
(plants)
ENZYME B
ENZYME A
MANY ENZYME CONTROLLED STEPS
ENZYME C
SORBITOL
ALTERNATIVE
ROUTE
SEVERAL
ENZYME
CONTROLLED
STEPS
Higher Biology Pupil Course Notes
Page 8 of 26 Duncanrig Secondary School CG 2015
Key Questions
Answer the following question in sentences.
1. Explain the meaning of the word metabolism.
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
2. Complete the following sentences by underlining the correct word in each bracket:
(a) Synthesis reactions are (anabolic / catabolic) and (require / produce)
energy.
(b) Breakdown reactions are (anabolic / catabolic) and (require / produce)
energy.
The answers can be checked using the PowerPoint that accompanies these
pupil course notes.
Higher Biology Pupil Course Notes
Page 9 of 26 Duncanrig Secondary School CG 2015
Toxic Effects of Poisons, Toxins and Venom on Metabolic Pathways
Poisons are substances that can disrupt metabolic pathways in cells following
absorption of the chemical through the skin, gut or lung lining.
Toxins are usually poisonous substances produced by a living organism.
Venom is a poisonous fluid secreted by certain snakes and scorpions.
Some examples and their effects on metabolic pathways are shown below (there are
more on the PowerPoint that accompanies the pupil course notes):
DEATH CAP MUSHROOMS
Death cap mushrooms are found widely in
Europe. When they are eaten, they inhibit
the enzyme RNA polymerase. The effects
are liver and kidney damage. Most
sufferers die within 6 – 10 days. There is
currently no known antidote.
CYANIDE
Once inhaled or ingested, cyanide inhibits
the enzymes located in the mitochondria
that are essential for producing ATP
during respiration. Hydrogen cyanide
was used in the gas chambers as a
method of execution.
BOTOX
Botulinum toxin kills its victims by causing
respiratory failure. It is a neurotoxin that
enters nerves and destroys vital proteins. It
is used as an anti wrinkle product. When
injected into the face it destroys the nerves
that cause frowning. The quantities used are
tiny - a few billionths of a gram.
ARSENIC
Arsenic oxides are tasteless, dissolve in
hot water and take less than a hundredth
of an ounce to kill. Yet in the 19th
Century, as a rat poison, it was cheap and
easily available. Arsenic trioxide has also
found a legitimate medical use, as an
anti-cancer agent.
Higher Biology Pupil Course Notes
Page 10 of 26 Duncanrig Secondary School CG 2015
Membranes
The cell membrane separates the internal contents of the cell from its external
surroundings. It controls the flow of materials into and out of the cell.
Membranes also surround organelles which compartmentalises functions within
the cell to either keep them close together or keep them apart. Some of these
organelles such as mitochondria and chloroplasts, have inner membranes which take
the form of folds or compartments.
The folding of membranes and organelles increases the surface area which allows
high concentrations of substances to accumulate and therefore increases
reaction rates. Small compartments like mitochondria and chloroplasts have a high
surface area to volume ratio.
inner folded membrane
outer smooth membrane
cristae
matrix
outer membrane
inner membrane
lamellae
stroma
granum
Higher Biology Pupil Course Notes
Page 11 of 26 Duncanrig Secondary School CG 2015
Structure of the Cell Membrane
The cell membrane consists of protein and phospholipid. The structure of the cell
membrane is described as a fluid mosaic model. This proposes that the
phospholipid bilayer component of the membrane is constantly moving. The patchy
arrangement of proteins that differ in size, structure and function throughout the
membrane are described as mosaic.
Add the following labels to the diagram of the fluid mosaic model of the cell
membrane.
LABELS: partially embedded protein surface protein pore
channel forming protein phospholipid
Role of Protein in the Cell Membrane
Pores
In order to transport larger molecules across the membrane, some proteins form
pores. They are described as channel forming proteins because they provide
channels for the diffusion of specific substances into or out of the cell.
Higher Biology Pupil Course Notes
Page 12 of 26 Duncanrig Secondary School CG 2015
Pumps
Active transport is the movement of molecules and ions across the cell membrane
against the concentration gradient, in other words, from low concentration to high
concentration. Active transport requires energy.
Certain proteins in the cell membrane act as carriers which can recognise specific
ions and transport them. These carriers are called pumps. Some of them play a
dual role exchanging one type of ion for another. An example of this is the
sodium/potassium pump (shown in the diagram below) where the same carrier
actively pumps sodium out of the cell and potassium into the cell each against its
own concentration gradient. This is important for the proper functioning of muscle
and nerve cells.
Protein pumps require energy. This is provided by respiration. As a result, factors
such as temperature, the availability of oxygen and food (respiratory substrate)
which affect the rate of respiration, will also affect the rate of active transport.
Enzymes
Some of the proteins embedded in the cell membrane are enzymes which control
the steps in a metabolic process essential to the cell. An example of this is ATP
synthase which catalyses the synthesis of ATP. ATP synthase is a protein found in
the membrane of mitochondria, chloroplasts and prokaryotes. Several enzymes can
also be arranged in the membrane as a multienzyme complex to promote a
series of related steps in a metabolic pathway.
INSIDE CELL
OUTSIDE CELL
Higher Biology Pupil Course Notes
Page 13 of 26 Duncanrig Secondary School CG 2015
Enzymes and Metabolism
Enzymes are biological catalysts that are responsible for speeding up chemical
reactions by lowering the activation energy. This is the energy needed to break
the chemical bonds in the reactants. The energy input in an uncatalysed reaction is
often in the form of heat meaning that the reaction will only proceed at a faster rate
if the temperature of the reactants is increased. In a catalysed reaction, the energy
input required to break the chemical bonds in the reactants is much lower. Because
of this, biochemical reactions can proceed relatively rapidly at much lower
temperatures.
Metabolic pathways rely on several enzymes that each control a single
step in a series of reactions. Therefore, metabolism is controlled by the
activity or inactivity of these key enzymes and the rate of metabolic
pathways is determined by the activity of each individual enzyme.
Progress of the Reaction
En
erg
y
Reactants
Products
Uncatalysed reaction
Catalysed reaction
higher activation energy required
lower activation energy required
Higher Biology Pupil Course Notes
Page 14 of 26 Duncanrig Secondary School CG 2015
Induced Fit
Enzymes have a groove or hollow on their surface that is called the active site.
Each enzyme acts on one type of substance – the substrate with the shape which
exactly fits into the enzyme’s active site. The theory that an enzyme and a substrate
fit together like a “lock and key” is not strictly true. A more accurate description of
the process would be that the enzyme’s active site is not a rigid structure, it is
flexible and dynamic. This means that the enzyme’s shape can alter to bind to the
substrate and then change back. The substrate induces the enzyme to change
shape and the enzyme has a high affinity for the substrate.
Here is an example:
The end products are released from the enzyme’s active site as the end products
have a low affinity for the active site.
A The two substrates enter the active
site of the enzyme because the
enzyme has a high affinity for them.
B Enzyme-Substrate Complex:
The enzyme changes shape forcing the
two substrates to combine.
(The dotted line indicates the original
shape of the enzyme)
C The enzyme has a low affinity for
the resulting product. Consequently,
the enzyme releases the product and
returns to its normal shape ready to
undergo more reactions.
Higher Biology Pupil Course Notes
Page 15 of 26 Duncanrig Secondary School CG 2015
Factors Affecting Enzyme Activity
Substrate Concentration: At low substrate concentrations, the reaction rate will
be slow as there are too few substrate molecules to make maximum use of all the
active sites of the enzymes. As the substrate concentration increases, the reaction
rate increases as more active sites are being used. A point is eventually reached
where a further increase in substrate concentration fails to cause an increase in
reaction rate because all active sites are occupied. Now, the enzyme’s
concentration has become the limiting factor. This effect is summarised in the
diagram below.
enzyme
(limited concentration) substrate
high concentration
medium concentration
very high concentration
+
+
+
+
enzyme-substrate complex
product produced (per unit of time)
low
medium
high
high
(limited due to the fact there are no more enzyme active sites available)
unused active sites
unused substrate
low concentration
Higher Biology Pupil Course Notes
Page 16 of 26 Duncanrig Secondary School CG 2015
Direction of Enzyme Action:
Metabolic pathways will usually involve a number of enzymes. A metabolic pathway
is shown below.
As the substrate becomes available, enzyme 1 will become active and convert the
substrate into metabolite A. In the presence of metabolite A, enzyme 2 becomes
active and converts A to B and so on. A continuous supply of substrate entering the
system will drive the sequence of reactions shown with the product of each
individual reaction acting as the substrate for the following reaction.
As mentioned before, most reactions are reversible; often one enzyme can catalyse
a reaction in both the forward and the reverse reaction. The direction will depend
on the concentrations of the reactant(s) and the product(s). In the example above,
if the concentration of C were to increase to an unusually high level, then enzyme 3
could go into reverse and convert C back into B until a more balanced state is
achieved.
ENZYME 5
ENZYME 6
ENZYME 4
ENZYME 1
ENZYME 2
ENZYME 3
SUBSTRATE(S)
METABOLITE B
METABOLITE A
METABOLITE C
END PRODUCT(S)
METABOLITE D
Higher Biology Pupil Course Notes
Page 17 of 26 Duncanrig Secondary School CG 2015
Use the diagram and the information on page 16 to answer the following questions
in sentences.
Key Questions
1) Which reaction in the metabolic pathway is reversible?
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
2) Metabolite C is toxic if it builds up, explain why this is not a problem.
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
3) If enzyme 3 is not produced, explain why metabolite B will not build up.
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
The answers can be checked using the PowerPoint that accompanies these
pupil course notes.
Enzyme Cofactors
Co-factors are molecules that are often needed to make the enzyme more
efficient. They can be inorganic such as iron, zinc, magnesium. They can also be
organic and are known as co-enzymes such as FAD and NAD (both involved in
respiration) and many vitamins.
Multi Enzyme Complexes
Some enzymes work in groups or in multi-enzyme complexes such as pyruvate
dehydrogenase complex. Pyruvate dehydrogenase has 3 enzymes that work together
to convert pyruvate into acetyl coA (a co-enzyme).
Higher Biology Pupil Course Notes
Page 18 of 26 Duncanrig Secondary School CG 2015
Control and Regulation of Enzymes and Metabolic Pathways
Regulation of enzyme activity can be controlled in several ways:
Enzyme Concentration – by controlling the concentration of the enzyme
present which is achieved by the switching “on” and “off” of the genes that
code for each enzyme as they are required.
Compartmentalisation – enzymes that are involved in the same metabolic
pathway are contained within the same cell organelle. For example, the
enzymes required for aerobic respiration are contained within the
mitochondria.
Enzyme Shape – by changing the enzyme shape, the efficiency of the
enzyme can be enhanced or reduced.
Higher Biology Pupil Course Notes
Page 19 of 26 Duncanrig Secondary School CG 2015
Lactose Metabolism in E.coli – the Lac operon
Some proteins are only required by a cell under certain circumstances. There is
evidence that, in such cases, genes that code for these proteins are switched on and
off as required. Two scientists called Jacob and Monod were the first to suggest this
idea of genes switching on and off after studying the bacterium Escherichia coli
(E.coli) this is known as the Jacob-Monod Hypothesis.
Lactose is a sugar found in milk. E.coli have the ability to synthesise an enzyme
called β-galactosidase that catalyses the breakdown of lactose into two types of
sugar (glucose and galactose):
lactose glucose + galactose
Jacob and Monod found that β-galactosidase is only manufactured when the E.coli
detects that there is lactose present, preventing the unnecessary wastage of
resources such as amino acids and energy. Therefore, the expression of the gene
for β-galactosidase is controlled. The process of switching on a gene only when the
enzyme is needed is called enzyme induction. How is this achieved?
An operon is made up of 2 separate genes;
Structural gene – codes for the enzyme in question (in this case, β-
galactosidase)
Operator gene – controls the structural gene
The activation of the operon is dependent on a third gene that is located nearby on
the DNA chain called the regulator gene. This codes for a repressor molecule.
It is the repressor that is responsible for controlling the operon depending on the
presence or absence of lactose. The diagrams on the next page summarise this.
β-galactosidase
Higher Biology Pupil Course Notes
Page 20 of 26 Duncanrig Secondary School CG 2015
The Lac Operon
ABSENCE OF LACTOSE
When lactose is absent, a repressor molecule (coded for by the regulator gene)
binds to the operator gene. This switches “off” the operator gene and prevents the
structural gene from switching “on” and being transcribed for the enzyme β-
galactosidase. Therefore, no β-galactosidase is made.
PRESENCE OF LACTOSE
When lactose is present, a repressor molecule (coded for by the regulator gene)
binds to lactose, the inducer instead of the operator. The operator gene now
switches on the structural gene, allowing the transcription of the code for the
enzyme β-galactosidase. The β-galactosidase is then made.
When all the lactose has been broken down, the repressor molecule no longer has
an inducer to bind to so now it binds to the operator gene, switching it off again.
regulator gene operator gene structural gene
regulator gene operator gene structural gene
switched on switched off switched off
REPRESSOR
MOLECULE
repressor molecule produced
repressor molecule
binds with operator no enzyme
X
switched on switched on switched on
repressor molecule produced
enzyme
produced repressor molecule
binds with the lactose
(the inducer)
LACTOSE
(INDUCER)
REPRESSOR
MOLECULE
REPRESSOR
MOLECULE
REPRESSOR
MOLECULE
Higher Biology Pupil Course Notes
Page 21 of 26 Duncanrig Secondary School CG 2015
Effect of Inhibitors on Enzyme Action An inhibitor is a substance that decreases the rate of an enzyme controlled reaction. There are two forms of inhibitor; competitive and non-competitive.
Competitive Inhibitors
A molecule of very similar shape to the substrate competes for the active site of the
enzyme, binding with it and therefore, reducing the overall concentration of the
enzyme that is available. This type of inhibition can be reversed by increasing the
concentration of the substrate. Competitive inhibition is summarised in the diagram
below.
Competitive inhibitor ABSENT:
Competitive inhibitor PRESENT:
+
enzyme
substrate
+
enzyme end products enzyme-substrate complex
showing induced fit
+
enzyme
substrate
+
enzyme-inhibitor complex unused
substrate
competitive
inhibitor
Higher Biology Pupil Course Notes
Page 22 of 26 Duncanrig Secondary School CG 2015
Non-competitive inhibitors
A non-competitive inhibitor does not directly bind with the enzyme’s active site.
Instead, it becomes attached to an non-active site called an allosteric site. This
interaction changes the shape of the enzyme’s active site indirectly and thus, the
enzyme cannot bind to the substrate. This is summarised in the diagram below.
Non-competitive inhibitor PRESENT:
Effect of Substrate Concentration
As the substrate concentration increases, the rate of reaction increases and then
becomes constant. This is linked to the number of available active sites as described
on page 14. Inhibitors will affect the rate of reaction in different ways and is
dependent on whether the inhibitor is competitive or non-competitive. The graph
below demonstrates this:
+
enzyme substrate
non-competitive
inhibitor
non-competitive inhibitor attached
to allosteric site on the enzyme
(NOT the active site) – causing a
change in the enzyme shape
+
substrate no longer
fits in the enzyme
active site
no inhibitor present: this is the point in the reaction
when all the active sites in the enzyme are occupied
substrate concentration
rate
of
rea
cti
on
competitive inhibitor present: increasing the substrate
concentration increases the rate of reaction gradually
because as the substrate molecules increase in number, they
outnumber those of the competitive inhibitor.
non competitive inhibitor present: increasing the
substrate concentration has no effect on the rate of
reaction. This is because the inhibitor has changed the
shape of the active site and it can no longer bind to the
substrate. Therefore, the rate of reaction remains low.
Higher Biology Pupil Course Notes
Page 23 of 26 Duncanrig Secondary School CG 2015
Feedback Inhibition by an End Product (End Product Inhibition)
End product inhibition is another way in which a metabolic pathway can be
regulated.
In the example above, as the concentration of the end product(s) increases, some of
the end product will bind to enzyme 1. This will slow down the conversion of the
substrate(s) to metabolite A. As the concentration of the end product(s) drops, the
effect it is having on enzyme 1 then decreases and therefore the pathway is under
constant regulation and fine tuning.
ENZYME 1
ENZYME 2
ENZYME 3
SUBSTRATE(S)
METABOLITE B
METABOLITE A
METABOLITE C
END PRODUCT(S)
METABOLITE D
ENZYME 4
ENZYME 5
ENZYME 6
Higher Biology Pupil Course Notes
Page 24 of 26 Duncanrig Secondary School CG 2015
An Example of End Product Inhibition: Phosphatase
Phosphatase is an enzyme that is found in a wide range of plant and animal
tissues (such as mung beans or beansprouts) where it reacts with a number of
different substrates to release phosphate groups. These phosphate groups are
important for the synthesis of ATP, phospholipids and nucleotides in living cells. An
artificial substrate called phenolphthalein phosphate (PPP) will react with
phosphatase to produce phenolphthalein (PP) and a free phosphate group (P).
This reaction is characterised by a colour change as the phenolphthalein is produced
from colourless to pink:
The more intense the pink colour, the more phenolphthalein is present. Therefore,
the more active the enzyme is, the more intense the pink colour. The intensity of
the pink colour produced can be measured and quantified using a colorimeter.
substrate enzyme products
phenolphthalein
phosphate (PPP)
phenolphthalein (PP) +
free phosphate (P)
phosphatase
COLOURLESS
PINK
(in alkaline conditions)
Higher Biology Pupil Course Notes
Page 25 of 26 Duncanrig Secondary School CG 2015
Sub topic 2.1 Regulation of Metabolism and Enzymes
How well do you rate your knowledge?
I am able to…….
State that metabolism is all the sum total of all the enzyme controlled chemical reactions occurring within a living cell.
State that anabolic pathways are synthesis reactions and require energy input.
State that catabolic pathways are breakdown reactions and are energy releasing.
State that metabolic pathways can have reversible and irreversible steps.
State that alternative routes can be taken to bypass steps in pathway.
State that membranes are a phospholipid bilayer with embedded and surface proteins.
State that membranes form surfaces and compartments to localise metabolic activity within the cell.
State that the folding of membranes and organelles increases the surface area which allows high concentrations to accumulate and this can increase reaction rates.
State that small compartments have a higher surface area to volume ratio than larger compartments.
State that proteins in the membrane form pores, pumps and enzymes.
State that metabolic pathways are controlled by the presence or absence of enzymes and the rate of activity of these key enzymes.
State that regulation of pathways can be controlled by intra and extra cellular signal molecules.
State that the activity of enzymes depends on their shape, and the ability of the substrate to bind to the active site.
Complete:
Column 1 – before your Unit assessment
Column 2 – before your Prelim
Column 3 – before your final exam
Higher Biology Pupil Course Notes
Page 26 of 26 Duncanrig Secondary School CG 2015
Describe the induced fit model of enzyme action.
State that substrates have a high affinity for the enzyme active site.
State that products have a low affinity for the enzyme active site.
Describe the effect of enzymes on the activation energy.
Describe how the substrate and end product concentrations can affect the direction and the rate of activity of the enzyme reaction.
State that metabolic reactions are reversible and the presence of a substrate or removal of a product will drive a sequence of reactions in a particular direction.
State that enzymes often act in groups or as multi enzyme complexes.
State that genes for some enzymes are continuously expressed.
Describe non competitive inhibition of enzyme action.
Describe competitive inhibition of enzyme action.
Describe how end product inhibition controls a metabolic pathway.