TCA cycle Flashcards

1
Q

Where does glycolysis, pyruvate processing, TCA cycle and ETC happen?

A

glycolysis: cytoplasm
pyruvate processing & TCA cycle: mitochondrial matrix ETC: inner membrane

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2
Q

What is cristae?

A

extensions of inner membrane
layers of sac like structures.
fill inside of mitochondria.
are connected to inner membrane by short tube

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3
Q

under hypoxic or anaerobic, what happens to pyruvate?

A

fermentation into ethanol or lactate

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4
Q

under aerobic conditions, what happens to pyruvate?

A

pyruvate –> acetyl-Coa –> produces CO2 and water

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5
Q

5 coenzymes required for pyruvate processing?

A

TPP
Lipoyl lisine (lipoamide)
FAD
NAD+
CoA-SH

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6
Q

Pyruvate processing catalyzed by which enzyme?

A

Pyruvate dehydrogenase complexe

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7
Q

Which 3 enzymes for pyruvate processing?

A

Pyruvate dehydrogenase
Dihydrolipoyl transacetylase
Dihydrolipoyl dehydrogenase

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8
Q

Pyruvate processing regulated by what?

A

Feedback inhibition: if products of glycolysis or pyruvate are abundant –> PDH is phosphorylated and inhibited through change in conformation

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9
Q

5 steps of pyruvate processing

A
  1. decarboxylation of pyruvate to aldehyde
  2. oxidation of aldehyde into carboxylic acid –> electrons reduce lipoamide to form thioester
  3. formation of acetyl-coA
  4. Reoxidation of lipoamide cofactor
  5. Regeneration of oxidized FAD cofactor –> forms NADH
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10
Q

FAD with which enzyme?

A

Dihydrolipoyl dehydrogenase

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11
Q

TPP with which enzyme?

A

Pyruvate dehydrogenase

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12
Q

Lipoyl lysine with which enzyme?

A

Dihydrolipoyl transacetylase

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13
Q

NAD and CoA-SH in which steps of pyruvate processing?

A

NAD in step 5 + CoA-SH in step 3

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14
Q

Does coenzyme A stay on enzyme’s structure?

A

No. associate, fulfill function, dissociate

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15
Q

Function of Coenzyme-A?

A

accept and carry acetyl groups –> carries remaining carbons from glucose to TCA cycle to be further oxidized

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16
Q

Multiple intermediates from CAC can be used as reactants in other metabolic pathways –> name?

A

Anaplerotic reactions

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17
Q

CAC = amphibolic?

A

Involves both catabolism and anabolism

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18
Q

Why anaplerotic reactions?

A

To replenish depleted cycle intermediates

19
Q

4 enzymes for anaplerotic reactions

A

pyruvate carboxylase
PEP carboxykinase (CO2 and GDP)
PEP carboxylase (HCO3-)
malic enzyme (pyruvate + HCO3- + NAD(P)H)

20
Q

first substrate of TCA cycle? how many carbons?

A

Acetyl-CoA –> 2C

21
Q

Rate limiting step of CAC cycle?

A

Step 1: citrate synthesis

22
Q

What does step 1 of TCA largely depend on?

A

Oxaloacetate concentration

23
Q

acetyl-CoA + oxaloacetate –> citrate

A

Step 1. Citrate synthase. F + I

24
Q

citrate –> isocitrate (passing through what?) + rationale?

A

passing through cis-aconitate. Step 2. Aconitase. U + R. secondary alcohol is a better substrate for oxidation

25
Q

Isocitrate –> alpha-ketoglutarate

A

Step 3. isocitrate dehydrogenase. decarboxylation. produces NADH and CO2. F + I

26
Q

alpha-ketoglutarate –> succinyl-CoA

A

Step 4. Alpha-ketoglutarate dehydrogenase. F + I. produces NADH and CO2

27
Q

Succinyl-CoA –> Succinate

A

Step 5. Substrate level phosphorylation. Succinyl-CoA synthetase. produces GTP. F + R

28
Q

Succinate –> fumarate

A

Step 6. Alkane to alkene. Succinate dehydrogenase (bound to inner membrane, act as complex II in ETC). equilibrium + R

29
Q

Fumarate –> L-malate

A

Step 7. Fumarase. water added (OH- and H+), always trans –> intermediate of carbanion. F + R

30
Q

L-malate –> oxaloacetate

A

Step 8. L-malate dehydrogenase. U + R. produces NADH!

31
Q

Which steps of TCA produce NADH?

A

Steps 3, 4 and 8. (2 decarboxylation and one during regeneration of oxaloactate)

32
Q

Which step of TCA produces FADH2?

A

Step 6. succinate to fumarate

33
Q

Which enzyme is similar to the pyruvate dehydrogenase complex?

A

alpha-ketoglutarate complex. same enzymes and mechanism but active sites different to accommodate different sized substrate

34
Q

Which molecule is has a high-energy thioester bond just like acetyl-CoA?

A

Succinyl-CoA

35
Q

When is there a net full oxidation of all glucose carbons?

A

Step 4 of TCA cycle. after 2nd decarboxylation –> forming succinyl-CoA

36
Q

What is formed at the end of TCA cycle?

A

2 CO2 + 3 NADH + FADH2 + GTP + CoA + 3 H+

37
Q

What is used during the TCA cycle?

A

1 Acetyl-CoA + 3 NAD+ + FAD+ + GDP + Pi + 2 H2O

38
Q

How many ATP produced after 1 glucose passes through TCA cycle?

A

21 ATP (10.5 per turn)
NADH –> 2.5 each
FADH2 –> 2 each
GTP –> 1 each

39
Q

Energy of which oxidations conserved to reduce NAD+, FAD+ and GDP?

A

Of step 3 and 4. both decarboxylations by isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase

40
Q

Which reaction is an isomerization in TCA cycle?

A

step 2: citrate to isocitrate catalyzed by aconitase

41
Q

Which step is a condensation reaction in TCA cycle?

A

Step 1: Oxaloacetate + acetyl-CoA –> citrate. by citrate synthase

42
Q

Which steps are oxidation reactions in TCA cycle?

A

Steps 3, 4, 6 and 8

43
Q

Which step is a hydration reaction in TCA cycle?

A

Step 7. fumarate to L-malate by fumarase

44
Q

Which step is a substrate level phosphorylation in TCA cycle?

A

Step 5. Succinyl-CoA to succinate