Oxidative phosphorylation:

Question 1

What has produced ATP so far in aerobic respiration?

Answer 1

• Substrate-level phosphorylation
• Phosphate group transferred to an intermediate ADP

Question 2

How does oxidative phosphorylation produce ATP?

Answer 2

• Flow of protons through ATP synthase

Question 3

Where does oxidative phosphorylation occur?

Answer 3

• Oxidative phosphorylation occurs across the inner mitochondrial membrane of the cristae
• The cristae are the inner folded membranes in mitochondria where the enzymes and proteins involved in oxidative phosphorylation are located
• Some of these proteins are involved in electron transfer chain: series of electron carrier molecules in the inner mitochondrial membrane that release energy in stages.

Question 4

Why is energy released in stages?

Answer 4

• More energy is harvested for benefit of the organism
• Less energy is released as heat

Question 5

Reactants of oxidative phosphorylation:

Answer 5

• Reduced NAD
• Reduced FAD
• Oxygen
• ADP and inorganic phosphate

Question 6

Products of oxidative phosphorylation:

Answer 6

• NAD
• FAD
• Water
• ATP

Question 7

Key steps in oxidative phosphorylation:

Answer 7

1. Reduced NAD and reduced FAD release hydrogen -> transfer protons (H+) and electrons (e-) into mitochondrial matrix
2. High-energy electrons are passed to an electron carrier from reduced NAD and reduced FAD.
3. The electrons are passed along a series of electron carrier molecules in the electron transfer chain embedded in the inner mitochondrial membrane, releasing energy as they are transferred.
4. The energy is used to actively transport protons across the inner mitochondrial membrane from the mitochondrial matrix into the intermembrane space.
5. The accumulation of protons in the intermembrane space sets up a steep electrochemical gradient of protons across the inner membrane.
6. Protons diffused back into the mitochondrial matrix down their electrochemical gradient through ATP synthase.
7. Energy released + catalyses the synthesis of ATP from ADP + Pi
8. Oxygen is the final electron acceptor and combined with electrons and protons to form water, helping to maintain the proton gradient

Question 8

Chemiosmosis:

Answer 8

• In aerobic respiration, chemiosmosis is the diffusion of protons across the partially permeable inner mitochondrial membrane
• down their electrochemical gradient through ATP synthase channels
• The movement of protons releases energy that is used to synthesise ATP
• Energy from electrochemical gradient is converted into chemical energy and stored in ATP

Question 9

ATP yield - glycolysis

Answer 9

ATP used - 2
ATP synthesised - 4
Net gain - 2

Question 10

ATP yield: link reaction

Answer 10

ATP used - 0
ATP synthesised - 0
Net gain - 0

Question 11

ATP yield: Krebs cycle

Answer 11

ATP used - 0
ATP synthesised - 2
Net gain - 2

Question 12

ATP yield: oxidative phosphorylation

Answer 12

ATP used - 0
ATP synthesised - approx 30
Net gain - approx 30

Question 13

Total ATP yield:

Answer 13

ATP used - 2
ATP synthesised - 36
Net gain - 34

Question 14

Which stage doesn’t contribute to overall yield of ATP?

Answer 14

Link reaction

Question 15

Which stage of respiration produced the most ATP?

Answer 15

Oxidative phosphorylation