electron transport chain

Question 1

What is the electron transport chain?

Answer 1

Embedded in mitochondrial membrane,

uses electrons from NADH and FADH2 produced by glycolysis,
pyruvate dehydrogenase, and the citric acid cycle for the production of ATP.

Regenerates FAD and NAD+ under aerobic conditions.

Question 2

What happens?

Answer 2

Electrons are donated by NADH and FADH2 to a chain of electron acceptors and donors.

Electrons fall to a lower energy state with each transfer.

Energy released by electrons creates a proton gradient, which drives ATP synthesis through an electrochemical gradient.

Question 3

What direction do electrons move in the chain?

Answer 3

From molecules of low reduction potential to molecules of high reduction potential.

Question 4

What do the electron transport chain and oxidative phosphorylation consist of?

Answer 4

Consists of 4 complexes (3 proton pumps) and 2 mobile electron carriers (ubiquinone and cytochrome c.

Receive electrons from NADH and FADH2. NADH enters at Complex 1. FADH2 enters at Complex 2.

Question 5

How many ATP and H+ are generated from NADH and FADH2?

Answer 5

NADH pumps 10H+ across the membrane, producing 3 ATP/NADH theoretically. FADH2 pumps 6H+ across membrane, producing 2 ATP/FADH2 theoretically.

Question 6

What is ubiquinone?

Answer 6

Also known as Q

small and hydrophobic, can diffuse through membrane, Can carry 1-2 electrons at a time.

Question 7

What are cytochromes?

Answer 7

They contain heme groups and carry 1 electron at a time.

Question 8

Complex 1

Answer 8

NADH Dehydrogenase, oxidized NADH to NAD+. Electrons pass through redox centers.

4H+ pumped into intermembrane space per electron pair.
Electrons transferred to Q, dissociates from enzyme.

Question 9

Complex 2

Answer 9

Succinate dehydrogenase, FADH2 oxidized to FAD.
No H+ pumping.
Electrons transferred to Q, dissociates from enzyme.

Question 10

Complex 3

Answer 10

Cytochrome c reductase, aka cytochrome b-c1 complex.
electrons passed from QH2 to cytochrome c1 via electron carriers.
Pumps 4H+ across membrane electron pair.

Question 11

Complex 4

Answer 11

Cytochrome oxidase, accepts electrons from 4 cytochrome c and passes them to O2.
Electrons passed along multiple redox centers. Pumps 2H+ across membrane per electron pair.