Electron Transport Chain

Question 1

Oxidative phosphorylation

Refers to the combination of:

Answer 1

1) Proton translocation from the electron transport chain.

2) Chemiosmotic coupling producing ATP.

Question 2

Oxidative phosphorylation

Chemiosmotic coupling

Answer 2

The ETC results in movement of protons (H+ ions) across the membrane.
This creates an electrochemical gradient which can be harnessed for energy.
Also called proton-motive force.

Question 3

Oxidative phosphorylation

ATP synthase

Answer 3

Harnesses the proton-motive force from diffusion of H+ ions through an ion channel to convert ADP to ATP.
Activity depends on # of NADH and FADH2 molecules in the mitochondrial matrix.
Also called complex V of the electron transport chain.

Question 4

Oxidative phosphorylation

ATP yield

Answer 4

Oxidative phosphorylation yields 1.5 ATP per FADH2 and 2.5 ATP per NADH.

Question 5

Electron transport chain complexes

Complex I

Answer 5

Also known as: NADH dehydrogenase

Reaction: Oxidizes NADH and reduces CoQ

H+ ions translocated: 4

Question 6

Electron transport chain complexes

Complex II

Answer 6

Also known as: Succinate dehydrogenase

Reaction: succinate + FAD → FADH2 + fumarate → CoQH2

H+ ions translocated: 0

Notes: Part of the citric acid cycle

Question 7

Electron transport chain complexes

Complex III

Answer 7

Also known as: Cytochrome c reductase

Reaction: The heme in cytochrome c gets reduced (Fe3+ → Fe2+) by CoQH2

H+ ions translocated: 4

Notes: Part of the q cycle which moves electrons from CoQH2 to cytochrome c

Question 8

Electron transport chain complexes

Complex IV

Answer 8

Also known as: Cytochrome c oxidase

Reaction: Transfers electrons from cytochrome c to oxygen, reducing it to water

H+ ions translocated: 2

Question 9

Electron transport chain principles

Answer 9

Each complex of the electron transport chain oxidizes an electron donor, starting with NADH.
The reduction potential increases until the final electron acceptor, oxygen, is reached.

Question 10

Electron transport chain principles

Location

Answer 10

Occurs in the inner mitochondrial membrane.

Question 11

Electron transport chain principles

Coenzyme Q (CoQ)

Answer 11

Also called ubiquinone. Important role in the electron transport chain as an electron acceptor for complexes I and II and delivering electrons to complex III.

Question 12

Electron transport chain principles

Q cycle

Answer 12

Describes the process of electrons moving from CoQH2 to cytochrome C.
Occurs through complex III of the ETC.

Question 13

Electron shuttle mechanisms

Answer 13

NADH is unable to cross the inner mitochondrial membrane.
Mechanisms to circumvent this are glycerol 3-phosphate and malate-asparatate

Question 14

Electron shuttle mechanisms

Glycerol 3-phosphate shuttle

Answer 14

Electrons get transferred from NADH to DHAP, forming glycerol 3-phosphate.
The electrons then get transferred to FAD in the mitochondria forming FADH2.

Question 15

Electron shuttle mechanisms

Malate-aspartate shuttle

Answer 15

Electrons get transferred from NADH to oxaloacetate, forming malate.
After the malate moves into the mitochondria, the electrons get transferred to NAD+ forming NADH.