Topic 5.1-4 Aerobic respiration

Question 1

State the purpose of aerobic respiration

Answer 1

Produces ATP, which can be hydrolysed to ADP + Pi

To release energy for metabolic reaction/ phosphoylate compunds to make the more reactive.

Question 2

Name the 4 main stages in aerobic respiration and where the occur

Answer 2

• Glycolysis - cytoplasm
• Link reaction - mitochondrial matrix
• Krebs cycle - mitochondrial matrix
• Oxidative phosphorylation via electron transport chain - membrane of the cristae

Question 3

Outline the stage of glycolysis

Answer 3

1. Glucose (a hexose sugar) is phosphorylated to glucose phosphate by 2x ATP
2. Glucose phosphate splits into 2x triose phosphate (TP)
3. 2x TP is oxidised to 2x pyruvate

Net gain of 2x reduced NAD and 2x ATP per glucose

Question 4

How does pyruvate from glycolysis enter the mitochondria?

Answer 4

Via active transport

Question 5

What happens during the link reaction?

Answer 5

1. Complete oxidation of pyruvate to acetate. Per pyruvate molecule: net gain of 1x CO₂ (decarboxylation) and 2H atoms (used to reduce 1x NAD)
2. Acetate combines with coenzyme A (CoA) to form acetylcoenzyme A

Question 6

Give a summary equation for the link reaction

Answer 6

Pyruvate + NAD + CoA

–>

acetyl CoA + reduced NAD + CO₂

Question 7

What happens in the Krebs cycle?

Answer 7

Series of redox reactions produces:
* ATP by substrate-level phosphorylation
* Reduced coenzymes e.g. NADH
* CO₂ from decarboxylation

Question 8

Outline the stages of the Krebs cycle

Answer 8

Look in text book

Question 9

What is the electron transport chain?

Answer 9

A series of carrier proteins embedded in membrane of the cristae of the mitochondria

Question 10

Name the process that the electron transport chain uses to produce ATP in aerobic repiration

Answer 10

Oxidative phosphorylation via chemiosmosis

Question 11

What happens in the electron transport chain?

Answer 11

Electrons released from reduced NAD and FAD undergo successive redox reactions.

The energy released is coupled to maintaining proton gradient or released as heat.

Oxygen acts as the final electron acceptor.

Question 12

How is a proton concentration gradient established during chemiosmosis in aerobic respiration?

Answer 12

Some energy released from the ETC is coupled to the active transport of H⁺ ions (protons) across the mitochondrial matrix into the intermembrane space.

Question 13

How does chemiosmosis produce ATP during aerobic respiration?

Answer 13

H⁺ ions move down their concentration gradient from the intermembrane space into the mitochondrial matrix via the channel protein ATP synthase.

ATP synthase catalyses ADP + Pi -> ATP

Question 14

State the role of oxygen in aerobic respiration

Answer 14

Final electron acceptor in electron transport chain.

(Produces water as a biproduct)

Question 15

What is the benefit of an electron transport chain rather than a single reaction?

Answer 15

• Energy is released gradually
• Less energy is released as heat