oxphos Flashcards

1
Q

where is oxphos carried out?

A

mitochondria (protein complexes in inner membrane)

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1
Q

what is the function of oxphos?

A

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

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2
Q

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

A

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)

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3
Q

which pumps in inner mitochondrial membrane are transmembrane + significance?

A

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

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4
Q

where does electron get transferred in proton pump 1?

A

NADH to CoQ (CoQH2)

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5
Q

where does electron get transferred in proton pump 2?

A

FADH2 to CoQ (CoQH2)

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6
Q

where does electron get transferred in proton pump 3?

A

CoQH2→ cytochrome C (reduced)

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7
Q

where does electron get transferred in proton pump 4?

A

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

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8
Q

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

A

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

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9
Q

how does ATP get synthesized from ETC?

A

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

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10
Q

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

A

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

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11
Q

what are the side products of oxphos (2)?

A
  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)
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12
Q

what enzymes help combat accumulation of toxic ROS?

A
  1. superoxide dismutase (superoxide)
  2. catalase (peroxide)
  3. glutathione peroxidase (peroxide)
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13
Q

how is ETC regulated?

A

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

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14
Q

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

A

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

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15
Q

what is oxphos mitochondrial disease?

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