Chapter 19

Question 1

Which complex accepts electrons from NADH?

Answer 1

Complex I

Question 2

Which complex accepts electrons from FADH2?

Answer 2

complex II

Question 3

What is the function of bc1 (complex III)

Answer 3

transfers electrons (one at a time) from QH2 to cytochrome C

Question 4

What is the function of the cytochrome oxidase complex (complex IV)

Answer 4

transfers electrons from cytochrome C to the terminal acceptor, oxygen

Question 5

Coenzyme Q (Ubiquinone)

Answer 5

Ubiquinone (Q) is a lipid-soluble compound that readily accepts electrons

Upon accepting two electrons, it picks up two protons to give an alcohol, ubiquinol

Ubiquinol can freely diffuse in the membrane, carrying electrons with protons from one side of the membrane to another side

Question 6

Overview of electron transport

Answer 6

4 cyt cred + 8 H+matrix + O2 —> 4 cyt cox + 2 H2O + 4 H+cytoplasm

Question 7

ATP synthase, complex V

Answer 7

Chemiosmotic hypothesis (Mitchell, 1961):

Proton gradient developed by electron transfer

Chemical gradient: change in pH across membrane

Electrical gradient: cytoplasmic side has positive charge

Called proton-motive force

Question 8

Partial reduction of oxygen

Answer 8

O2 has high affinity for electrons

Partial reduction can happen

Single electron transfer gives superoxide radical

Two electron transfer gives peroxide

Small amounts of these are inevitable

Question 9

Reactive oxygen species (ROS)

Answer 9

Superoxide, hydroxyl radical, singlet oxygen

Highly destructive

Thought to be involved in aging process, other disease processes

Anti-oxidants target these molecules

Question 10

Superoxide dismutase (SOD),

Answer 10

SOD protects by converting superoxide radicals into O2 and hydrogen peroxide (H2O2)

Mutations in superoxide dismutase cause some familial ALS, a neurodegenerative disorder.

Hydrogen peroxide is converted to O2 and water by Catalase or Peroxidase