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What are anabolic reactions?

biochemical reactions where large molecules are synthesised from smaller ones.


What are catabolic reactions?

When larger molecules are hydrolysed to produce smaller molecules.


What is glycolysis?

A metabolic pathway where each glucose molecule is broken down to two molecules of pyruvate.
It occurs in the cytoplasm of all living cells.


What is hydrolysis?

The breaking down of large molecules to smaller molecules by the addition of water.


What is the site if the link action, Krebs cycle and oxidative phosphorylation?



What does the link reaction do?

Converts pyruvate to acetate.
NAD is reduced.


What does the Krebs cycle do?

Oxidises acetate to carbon dioxide.
NAD and FAD are reduced.
ATP is made by substrate level phosphorylation.


What is oxidative phosphorylation?

The formation of ATP by adding a phosphate group to ADP.
In the presence of oxygen which is the final electron acceptor.


What is chemiosmosis?

The diffusion of hydrogen ions through a partially permeable membrane, which is coupled to the generation of ATP.


What is anaerobic respiration?

The release of energy from subtrates, such as glucose, in the absence of oxygen.


What is a respiratory substrate?

An organic substrate that can be used for respiration.


Give examples if why we need to respire.

Active transport.
Replication of DNA/interphase.
Cell replication, meiosis.


Describe the structure of ATP.

Ribose sugar.
3 phosphate.

Can be hydrolysed to ADP and an inorganic phosphate.


What is the role of NAD?

Carries hydrogen atom which can later be split to H+ and e-


What are the products of glycolysis?

2 x ATP (4 made but 2 used)
2 x red NAD
2 x pyruvate


Describe the stages of glycolysis.

One ATP molecule is hydrolysed and the phosphate group attaches the glucose molecule at carbon 6.

Glucose-6-phosphate is changed to fructose-6-phosphate.

Another ATP is hydrolysed and attaches to fructose at C1. Now fructose 1,6-bisphosphate.
Becomes Hexose 1,6-bisphosphate.

Each molecule of H1,6B us split into two molecule of triose phosphate.

Using dehydrogenase enzymes two hydrogen atoms are removed from each triose phosphate molecule.

NAD combines with the H atoms to form red NAD.

2 molecules of ATP are formed - substrate level phosphorylation.

Enzyme catalysed reactions convert each triose phosphate molecule to pyruvate.
2 molecules of ADP are also phosphorylated by substrate level p.


Describe the ultrastructure of mitochondria.

An intermembrane space between the inner and outer phospholipid membrane.

Outer membrane is smooth
Inner membrane is folded into cristae to give a larger surface area.

The matrix is enclosed by the inner membrane, contains proteins, lipids, enzymes etc.


How does mitochondria structure help them carry out their function?

Enzymes to catalyse reactions.
Contains coenzyme NAD. Ribosomes where proteins are assembled.
Mitochondrial DNA to code for enzymes and proteins.

Outer membrane:
Channel/carrier proteins to allow pyruvate to pass.

Inner membrane:
Impermeable I most small ions, eg H+.
Folded cristae gives large surface area.
Electron carriers and ATP synthase enzymes embedded in it.


Describe electron carriers.

Protein complexes arranged in electron transport chains.

Each electron carrier is an enzyme, with haem cofactors, containing iron

Cofactor can accept and donate electrons as iron Fe2+ oxidised/reduced and donating to the next carrier.

Oxidoreductase enzymes in reduction and oxidation reactions.

Some carriers have a coenzyme that pump protons from the matrix to the intermembrane space.

Because the inner membrane is impermeable to small ions protons accumulate in the IM space, a source of energy.


Describe the ATP synthase enzymes.

Large and protrude from the inner membrane into the matrix.

Allow protons to pass through them down a concentration gradient (chemiosmosis).

The proton motive force drives the rotation if part of the enzyme and joins ADP to pi.


Describe the link reaction.

Pyruvate dehydrogenase and decarboxylase remove H and a carboxyl group from pyruvate.

This produces CO2.
Coenzyme NAD accepts the H.
Coenzyme A accepts acetate to become acetyl coenzyme A.


How is ATP indirectly made from the link reaction?

Red NAD carries2 H atoms to be used in oxidative phosphorylation.


Describe the Krebs cycle.

Acetate is offloaded by coenzyme A and joins oxaloacetate to form citrate.

Citrate is deC and deH to form a 5C compound.
This produces CO2 and a molecule of NAD accepts 2 H to become red.

5C is deC and deH to form a 4C compound.
CO2 and red NAD.

4C changed to another 4C.
SLP makes ADP phosphorylated to ATP.

4C changed to 4C, pair of H removed and accepted by coenzyme FAD to become red.

4C deC and deH to regenerate oxaloacetate.
Another NAD is red.


What is the frequency of the Krebs cycle?

One turn for each molecule of acetate, since link produces 2 acetate per 1 pyruvate.

2 turns per glucose.


What are the products of the link reaction?

2 red NAD
2 CO2


What are the products of the Krebs cycle?

6 red NAD.
2 red FAD.
4 CO2.
2 ATP.


Where does oxidative phosphorylation occur?

Inner mitochondrial membrane.


Describe how oxidative phosphorylation occurs?

Chemiosmosis occurs.

The electrons are passed from the last electron carrier to oxygen, which is the final electron acceptor.

H+ also join so oxygen is reduced to water.


Why is the potential number of ATP molecules in oxidative phosphorylation rarely met?

Protons leaking across the mitochondrial membrane reduced the proton motive force.

Some ATP actively transports pyruvate into the mitochondria.


Describe how animals respire anaerobically?

Lactate fermentation.
When the ATP demand is high and there is an oxygen deficit.

Red NAD is oxidised to NAD.
Pyruvate is a hydrogen acceptor.
It accepts H from red NAD.

Lactate dehydrogenase catalyses oxidation of red NAD and reduction of pyruvate to lactate.

Can be recycled to glucose/glycogen.
Can be carried to the liver and converted back to pyruvate if oxygen is present.