18.4 Oxidative Phosphorylation

Question 1

What is oxidative phosphorylation?

Answer 1

phosphorylation of ADP

for which energy is supplied

by electron transport chain

Question 2

18.4 Oxidative Phosphorylation

Outline the processes which occur during Oxidative Phosphorylation within the mitochondria:

Answer 2

1. NADH & FADH₂ supply H atoms to cristae of mitochondria
2. H atoms dissociate ⟶ H⁺ + e^-
3. These high-energy electrons take part in electron transport chain, releasing energy for active transport of H⁺ across mitochondrial membrane.
4. H⁺ diffuse through ATP synthase protein, driving the phosphorylation of ADP ⟶ ATP by chemiosmosis.
5. At end of electron transport chain, electrons combine with H atoms (delivered from coenzymes) + O₂ ⟶ H₂O
   
   1. O₂ is final electron acceptor, without it the electron transport chain cannot occur.

Question 3

18.4 Respiration

What is the final electron acceptor in the electron transport chain?

Answer 3

Oxygen

Question 4

18.4 Oxidative Phosphorylation

What supplies the H⁺ + e^- to the electron transport chain in the mitochondria?

Answer 4

Coenzymes reduced NAD & reduced FAD

(NADH + FADH₂ release hydrogen atom(s), which dissociate into H⁺ for the proton gradient and e^- for the electron transport chain)

Question 5

What is substrate-level phosphorylation?

Answer 5

Phosphorylation of ADP to ATP

using a phosphate from a short-lived, highly reactive intermediate

Question 6

Where in the cell does oxidative phosphorylation occur during respiration?

Answer 6

Cristae of mitochondria

Question 7

Explain why FADH₂ does not synthesise as many ATP molecules as NADH:

Answer 7

FADH₂ supplies electrons to the electron transport chain further on than NADH

electrons from FADH2 release less energy

less H⁺ are actively transported across thylakoid membrane to create proton gradient

less H⁺ diffuse by facilitated diffusion through ATP synthase protein

less ATP molecules produced