Carbs 4 - CAC Flashcards

1
Q

Summarize CAC

A

CAC is a gateway to aerobic metabolism for any molecule capable of being broken down to one of CAC’s intermediates.
It removes electrons as H atoms and binds them to carriers prducing NADH and FADH2 which transfer them to the electron transfer chain (respiratory chain) which produces ATP.

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2
Q

Why is o2 necessary for aerobic respiration?

A

O2 acts as an oxyen acceptor at the end of teh respiratory chain.
Without it the whole pathway of CAC & the respiratory chain si energetically unfavourable and so wouldnt occur.

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3
Q

What 3 reactions produce Acetyl CoA from Pyruvate?

A

Decarboxylation (whihc produces 2 electrons for ATP)
Oxidation
Transfer of the CoA complex

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4
Q

What enzyme catalyzes pyruvate -> Acetyl CoA?

A

Pyruvate Dehydrogenase

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5
Q

How many sub-units and copies make up pyruvate dehydrogenase?

A

Pyruvate dehydrogenase is a massive enzyme made up of 3 sub-units (E1,E2,E3) each of which has 10 copies in one enzyme.

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6
Q

Which sub-units catalyze which part of the pyruvate -> Acetyl CoA reaction pathway?

A

E1 - decarboxylation
E2 - transfers the Acetyl roup to coenzyme A
E3 - recycles lipoyllysine by reducing FAD to FADH2 which becomes 2x NADH.

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7
Q

Why is the clyclic section of CAC known as the “black box”?

A

Because all the intermediate components remain constant.

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8
Q

How does Carbon enter & leave the CAC?

A

Every turn of the cycle 2 carbons enter as Acetyl CoA and 2 CO2 molecules leave. It is actually the same CArbons that enter as leave.

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9
Q

Which 3 enzymes can be regulated as points of control in CAC?

A

Pyruvate dehydrogenase
Alpha-ketoglutare dehydrogenase
Isocitrate dehydrogenase

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10
Q

What ergulates pyruvate dehydrogenase?

A

ATP and the enzymes immediate products regulate its use so it can be regualted according to the cells needs

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11
Q

wHAT REGULATES ISOCITRATE DEHYDROGENASE?

A

Allosterically regulated by ATP and NADH (negative) and ADP (positive)

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12
Q

What regulates alpha-ketolutarate dehydrogenase?

A

Allosterically regulated by ATP, NADH and succinyl CoA (all negative).

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13
Q

Which 2 enzymes in CAC catalyze irreversible (exergonic) reactions?

A

Isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase

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14
Q

What use is blocking isocitrate dehydrogenase?

A

Blockin isocitrate dehydrogenase causes a build up of citrate which ends up in the cytoplasm and causes phosphofuctokinase to block glycolysis.

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15
Q

What use is blocking alpha-ketoglutarate dehydrogenase?

A

builds up alpha-ketolutarate which is used producing amino acids.

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