Week 12

Question 1

Alternative name and action of Complex I?

Answer 1

NADH dehydrogenase (NADH–CoQ reductase); transfers electrons from NADH to coenzyme Q and pumps protons into the intermembrane space.

Question 2

Alternative name and action of coenzyme Q?

Answer 2

Ubiquinone; mobile electron carrier that transfers electrons from Complex I and II to Complex III.

Question 3

Alternative name and action of Complex II?

Answer 3

Succinate dehydrogenase; transfers electrons from FADH₂ (succinate → fumarate) to coenzyme Q.

Question 4

How is Complex II different from Complex I, III, and IV?

Answer 4

Complex II does NOT pump protons across the membrane.

Question 5

Alternative name and action of Complex III?

Answer 5

Cytochrome bc₁ complex (CoQ–cytochrome c reductase); transfers electrons from coenzyme Q to cytochrome c and pumps protons.

Question 6

Alternative name and action of Complex IV?

Answer 6

Cytochrome c oxidase; transfers electrons from cytochrome c to oxygen forming water and pumps protons.

Question 7

Function of cytochrome c?

Answer 7

Mobile electron carrier that transfers electrons from Complex III to Complex IV.

Question 8

Function and structure of Complex V?

Answer 8

ATP synthase; uses proton gradient to synthesize ATP from ADP and Pi. Structure: F₀ (membrane proton channel) + F₁ (ATP-producing head).

Question 9

What is the chemiosmotic (Mitchell) hypothesis and proton-motive force?

Answer 9

ATP is generated using energy stored in a proton gradient across the inner mitochondrial membrane. Proton-motive force = electrochemical gradient of protons that drives ATP synthesis.

Question 10

What are uncoupling proteins and how do they work?

Answer 10

Proteins that allow protons to re-enter the matrix without making ATP, releasing energy as heat.

Question 11

Natural vs synthetic uncouplers?

Answer 11

Natural: Thermogenin (UCP1 in brown fat). Synthetic: 2,4-DNP and high-dose aspirin.

Question 12

What are respiratory chain inhibitors?

Answer 12

Substances that block electron transport: Rotenone (Complex I), Cyanide & CO (Complex IV), Oligomycin (Complex V).

Question 13

Purpose of glycerol phosphate and malate-aspartate shuttles?

Answer 13

Transfer cytosolic NADH electrons into mitochondria for ATP production.