oxphos

Question 1

where is oxphos carried out?

Answer 1

mitochondria (protein complexes in inner membrane)

Question 1

what is the function of oxphos?

Answer 1

generate ATP from reducing equivalents (NADH, FADH2 fr glycolysis & TCA cycle)

Question 2

how does NADH fr glycolysis [cytoplasm] enter mitochondria? (2)

Answer 2

shuttles:
1. glycerol-3-phosphate shuttle: brings NADH in as FADH2 (fast but less ATP eg muscles)
2. malate-aspartate shuttle: brings NADH in as NADH (slow but more ATP eg cardiac/liver muscles)

Question 3

which pumps in inner mitochondrial membrane are transmembrane + significance?

Answer 3

1, 3, 4
transmembrane→ can pump H+ across to maintain electrochemical gradient

Question 4

where does electron get transferred in proton pump 1?

Answer 4

NADH to CoQ (CoQH2)

Question 5

where does electron get transferred in proton pump 2?

Answer 5

FADH2 to CoQ (CoQH2)

Question 6

where does electron get transferred in proton pump 3?

Answer 6

CoQH2→ cytochrome C (reduced)

Question 7

where does electron get transferred in proton pump 4?

Answer 7

cytochrome C (reduced) to O2→ H2O! :)
O2 is final electron acceptor

Question 8

how does electron get transferred from proton pumps 1 to 4 (summary)

Answer 8

NADH and FADH2 to CoQ→ cytochrome C→ O2⇒ H2O

Question 9

how does ATP get synthesized from ETC?

Answer 9

proton gradient formed across inner mitochondrial membrane by pumping of H+ by pumps 1,3,4

H+ flow through ATP synthase catalyzes formation of ATP fr ADP+Pi

Question 10

what is the breakdown of the total amt of ATP produced by glycolysis/TCA/oxphos per glucose molecule?

Answer 10

glycolysis: 2ATP
TCA cycle: 2ATP + 8NADH + 4FADH2
oxphos:
- 8NADH = 20ATP
- 4FADH2 = 6 ATP
total= 30ATP

Question 11

what are the side products of oxphos (2)?

Answer 11

1. reactive oxygen species (partial reduction of O2→ toxic derivatives)
2. heat (short circuit UCP channel in brown fat allowing H+ to pass wo ATP synthase)

Question 12

what enzymes help combat accumulation of toxic ROS?

Answer 12

1. superoxide dismutase (superoxide)
2. catalase (peroxide)
3. glutathione peroxidase (peroxide)

Question 13

how is ETC regulated?

Answer 13

based on ATP need:
high ATP consumption→ increase H+ flow→ decrease H+ gradient→ increase ETC flow
low ATP consumption opposite

Question 14

what mitochondrial poisons inhibit what mechanisms of oxphos? (4)

Answer 14

Rotenone/Rat poison: ETC pump 1
Antimycin A/fish poison: ETC pump 2
Cyanide/CO: ETC pump 3
Dinitrophenol/herbicide/weight loss drug: increase proton leak against membrane→ short circuit→hyperthermia

Rats Are Cats Dinner

Question 15

what is oxphos mitochondrial disease?

Answer 15

• genetic disease (maternal inheritance)
• e.g. MELAS syndrome: mutation in tRNA gene→ decrease ETC complexes→ decrease ATP & accumulation of pyruvate→ organ dysfunction & lactate acidosis