What are the four stages of

Glycolysis?

(4 marks)

1) Activation of glucose by phosphorylation

2) Splitting of the phosphorylated glucose into triose phosphate

3) Oxidation of triose phosphate

4) The production of ATP

Describe the process by which glucose is

converted into triose phosphate during

glycolysis.

(3 marks)

1) Glucose is made more reactive by the addition of two phosphate molecules.

2) The phosphate molecules come from

the hydrolysis of ATP into ADP.

3) This lowers the activation energy for

enzyme-controlled reactions.

Describe how ATP is made from glucose in glycolysis.

(4 marks)

1) Glucose is activated by phosphate from the hydrolysis of ATP to ADP and forms two molecules of triose phosphate.

2) Triose phosphate is oxidised. This means that hydrogen is removed from each triose phosphate molecule.

3) This hydrogen is transferred to a hydrogen-carrier molecule called NAD. This reduces NAD to form Reduced NAD.

4) Enzyme-catalysed reactions convert each triose phosphate molecule into pyruvate, producing energy to convert ADP to ATP.

*Red words are needed for the mark.

What is aerobic respiration?

(2 marks)

1) The breakdown of glucose involving oxygen...

2) ...to produce energy in the form of ATP.

*Red words are needed for the mark.

Name the products of glycolysis

from the breakdown of one glucose

molecule.

(3 marks)

1) Two molecules of ATP (4 molecules made, but two were used in phosphorylation.)

2) Two molecules of Reduced NAD.

3) Two molecules of pyruvate.

*Words marked in red are needed for the mark.

What are the reactants in the

link reaction?

(3 marks)

1) Pyruvate

2) NAD

3) Coenzyme A/CoA

What are the products of the

link reaction?

(3 marks)

1) Acetyl Coenzyme A/Acetyl CoA

2) Reduced NAD

3) Carbon Dioxide/CO₂

*Words in red are needed for the mark.

Where does the link reaction

occur in an animal cell?

(1 mark)

In the matrix of the mitochondria.

*Words in red are needed for the mark.

How many carbon molecules are

in one molecule of

pyruvate?

(1 mark)

3 Carbon molecules

Acetyl CoA is made from pyruvate and Coenzyme A combining in the link reaction.

How many molecules of carbon are in

Acetyl CoA?

(1 mark)

2 molecules of Carbon.

Starting from Acetyl CoA, how is ATP formed in the Krebs' cycle?

(3 marks)

1) Acetyl CoA binds with a 4-carbon molecule to make a 6-carbon molecule.

2) CO₂ and Hydrogen is lost from the 6-carbon molecule. (It is oxidised.)

3) ATP is produced as a result of substrate-level phosphorylation.

*Words in red are needed for the mark.

Describe the roles of coenzymes in

aerobic respiration.

(3 marks)

1) Act as hydrogen-carrier molecules

2) Has the potential to produce ATP...

3) ...via the Electron Transport Chain (ETP).

*Red words are needed for the mark.

The Krebs' Cycle is a significant biochemical

process which occurs in the cells of organisms. Describe and explain its role in

the cells of organisms.

(5 marks)

1) It breaks down macromolecules into smaller molecules.

2) Produces Hydrogen atoms/H⁺ ions...

3) ...which are carried by coenzymes/hydrogen-carrier molecules/NAD and FAD...

4) ...to produce energy as ATP.

5) Regenerates the 4-carbon molecule to combine with Acetyl CoA to stop accumulation in the cell

6) It is a source of intermediate compounds used by cells to manufacture other important substances.

*Words in red are needed for the mark.

*You only need 5 out of 6 points to achieve full marks.

Where does the Electron Transport Chain

(ETP) take place in an animal cell?

(2 marks)

1) In the matrix of the mitochondria...

2) ...on the cristae/folds of the inner membrane.

*Words in red are needed for the mark.

Hydrogen atoms are required for ATP to be

made via the ETP. Describe and explain

how hydrogen atoms in glucose are transferred to the ETP.

(6 marks)

1) In Glycolysis, glucose is phosphorylated and broken down into two molecules of triose phosphate.

2) Triose phosphate is oxidised to pyruvate and loses hydrogen atoms. These are carried by NAD, forming Reduced NAD.

3) Pyruvate is oxidised and loses CO₂ and hydrogen, which is carried by NAD forming Reduced NAD. 

4) Acetyl CoA formed in the link reaction binds with a 4-carbon molecule in the Krebs' cycle to make a 6-carbon molecule.

5) The 6-carbon molecule is oxidised, and loses CO₂ and hydrogen, which is taken up by NAD and FAD, forming Reduced NAD and FAD.

6) Coenzymes from glycolysis, the link reaction and the Krebs' Cycle donate their hydrogen atoms to the first carrier in the ETP.

*Words in red are required for the mark.

*Underlined words also count for the mark, but they do not have to be the exact same.

Explain why metabolically active cells contain a lot of mitochondria.

(3 marks)

1) The mitochondria is the organelle where the main stages of aerobic respiration take place.

2) Aerobic respiration yields a large amount of energy in the form of ATP.

3) ATP is required for metabolic processes, such as...

(muscle contraction, active transport, secretion, activation of molecules, synthesis of DNA/RNA/polypeptides/polysaccharides)

*Words in red are required for the mark.

*Underlined words are also required, but do not have to be exact.

Explain why the mitochondria is the

site of the Electron Transport Chain (ETP).

(2 marks)

1) The inner membrane of the mitochondria is folded (cristae) which provides a large surface area.

2) Allows the attachment of enzymes and other proteins involved in electron transport.

*Words in red are required for the mark.

*Underlined words are required for the mark, but not exact.

Explain how ATP is synthesised using the

Electron Transport Chain (ETP), resulting in water as a by-product.

(8 marks)

1) Hydrogen atoms produced during glycolysis and the Krebs' Cycle combine with NAD and FAD, forming Reduced NAD and FAD.

2) Reduced NAD and FAD donate the electrons of the hydrogen molecules they are carrying to the first carrier of the ETP.

3) Protons are released from the hydrogen atoms and are actively transported across the mitochondrial membrane.

4) The electrons are passed along a chain of electron transport molecules in a series of redox reactions.

5) The electrons lose energy at each redox reaction, which is used to combine ADP and P' to form ATP.

6) Protons accumulate on the other side of the mitochondrial membrane and diffuse back into the matrix via protein channels.

7) Oxygen is the final electron acceptor in the ETP.

8) The electrons and protons combine with oxygen to form water.

*Words in red are required for the mark.

*Underlined words are also required, but not exact.

Explain why oxygen is required for aerobic

respiration.

(3 marks)

1) Oxygen is the final electron acceptor in the Electron Transport Chain.

2) Oxygen removes the hydrogen atoms produced in glycolysis and the Krebs' cycle.

3) This prevents the inhibition of the process of respiration.

*Words in red are required for the mark.

*Underlined words are also required, but are not exact.