LECTURE 22 - OXIDATIVE PHOSPHORYLATION

Question 1

List the electron carriers in the electron transport chain

Answer 1

NAD & NADH
FADH & FADH2

MOBILE:
CoQ
Cytochrome C

Question 2

List the reductants in the electron transport chain

Answer 2

Complex I - NADH
Complex II - Succinate
Complex III - Reduced CoQ(H2)
Complex IV - Cytochrome C

Question 3

List the oxidants in the electron transport chain

Answer 3

Complex I - Flavin mononucleotide (FMN)
Complex II - Flavin adenine dinucleotide (FAD)
Complex III - Cytochrome C
Complex IV - Oxygen (O2)

Question 4

What are the reductants and oxidants involved in Complex I?

Answer 4

Reductant: NADH
Oxidant: Flavin mononucleotide (FMN)

Question 5

What are the reductants and oxidants involved in Complex II?

Answer 5

Reductant: Succinate
Oxidant: Flavin adenine dinucleotide (FAD)

Question 6

What are the reductants and oxidants involved in Complex III?

Answer 6

Reductant: Reduced Coenzyme Q (CoQH2)
Oxidant: Cytochrome c

Question 7

What are the reductants and oxidants involved in Complex IV?

Answer 7

Reductant: Cytochrome c
Oxidant: Molecular Oxygen (O2)

Question 8

Identify the inhibitor(s) of Complex 1 and their mechanism of inhibition

Answer 8

Rotenone (pesticide)
Prevents usage of NADH
– Same results as if one does not have oxygen

Question 9

Identify the inhibitor(s) of Complex IV and their mechanism of action

Answer 9

Inhibited by cyanide (CN–), azide (N3–), and carbon monoxide (CO)

Bind to iron in heme of cytochrome c oxidase

People who die of carbon monoxide poisoning turn pink

Question 10

List the inhibitors of the Electron Transport Chain

Answer 10

Complex I = Rotenone
Complex IV = cyanide (CN–), azide (N3–), and carbon monoxide (CO)

Question 11

Describe the mechanism of energy loss caused by uncouplers

Answer 11

Dissipate the proton gradients by shuttling protons across the inner mitochondrial membrane
– Oxygen is consumed without ATP synthesis
– Energy is lost as heat

Question 12

Describe the function of uncoupling proteins in humans

Answer 12

Dissipates the proton gradient & causes nonshivering thermogenesis
– Produces heat
– Important for newborns

Question 13

Explain how the electron transport chain minimizes the production of reactive oxygen species

Answer 13

Cytochrome c oxidase catalyzes the reduction of O2 to water by passing one electron at a time without releasing the intermediates

(However, ROS’s can still escape via leakage)

Question 14

Identify key enzymes that remove reactive oxygen species

Answer 14

Superoxide dismutase (primary)
Catalase (primary)

Glutathione peroxidase
– Uses glutathione as a reductant.
– Oxidized glutathione is reduced by glutathione reductase using NADPH

Question 15

Identify the organs and tissues especially sensitive to reactive oxygen species in diabetic patients

Answer 15

Retina
Kidney
Peripheral nerves