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Biochem test 3 > L 24: TCA cycle > Flashcards

L 24: TCA cycle Flashcards

1
Q

What type of reactions are required during states of low energy?

A

Anaplerotic reactions

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2
Q

The citric acid cycle is a source of ?

A

Biosynthetic precursors

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3
Q

By what 2 ways is Pyruvate Dehydrogenase Complex (PDH or PDC) regulated

A

Allosterically

Phosphorylation

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4
Q

How many carbon units does the citric acid cycle oxidize?

A

TWO

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5
Q

True or false

Entry into the citric acid cycle and metabolism through it are not highly controlled

A

False, Both are high controlled

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6
Q

The citric acid cycle takes place where?

A

Mitochondria

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7
Q

The oxidation of 2-carbon units to produces what?

A
  • 2 CO2 molecules
  • 1 GTP
  • High energy electrons in the form of NADH and FADH2
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8
Q

Acetyl CoA is obtained from what three energy nutrients?

A

Carbohydrates
Lipids
Proteins

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9
Q

What is the activated form of acetate?

A

Acetyl CoA

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10
Q

What are the 3 steps of Acetyl CoA from pyruvate

A
  • Decarboxylation
  • Oxidation
  • Transfer acetyl group to coenzyme A
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11
Q

Steps for Aerobic Glycolysis chain oxidative phosphorylation (pyruvate entering mitochondria)

A
  1. Pyruvate must enter mitochondria
  2. Pyruvate utilize mitochondrial pyruvate carrier (MPC)
  3. Pyruvate dehydrogenase complex (PDC) catalyzes the decarboxylation of pyruvate
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12
Q

What 3 enzymes are required in the pyruvate dehydrogenase reaction

A

E1,E2,E3

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13
Q

What 5 coenzymes are required in the pyruvate dehydrogenase reaction

A 
Catalytic factor:
*Thiamine pyrophosphate TPP
* Lipoic acid
*FAD
Stoichiometric cofactors
*CoA
*NAD+
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14
Q

What does the Pyruvate Dehydrogenase Complex do?

A

Catalyzes the decarboxylation of pyruvate into:

Acetyl CoA+Co2+NADH+H

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15
Q

High Acetyle CoA directly inhibits what?

A

E2 by phosphorylation

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16
Q

When regulating PDC the accumulation of ADP and pyruvate activate what?

A

Phosphatases

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17
Q

All energy containing nutrients should be converted to what?

A

Acetyl CoA

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18
Q

TCA occurs under what type of conditions?

A

Aerobic

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19
Q

True or False

TCA produces more energy from glucose than glycolysis?

A

True

20
Q

What links glycolysis to the TCA?

A

Pyruvate dehydrogenase (PDH)

21
Q

The first step of the TCA cycle does what?

A

Condensation of 4-carbon oxaloacetate and 2-carbon acetyl group of acetyl CoA

22
Q

What enzyme catalyzes Oxaloacetate to Citrate

A

Citrate synthase

23
Q

What enzyme isomerizes citrate to isocitrate

A

Aconitase moves OH atom via dehydration/hydration rxn

24
Q

What enzyme completes the first oxidation-reduction rxn of isocitrate to Alpha-Ketoglutarate

A

Isocitrate dehydrogenase

25
Q

What is the unstable intermediate formed by the rxn of Isocitrate and isocitrate dehydrogenases?

A

Oxalosuccinate

26
Q

What is the rate limiting step of the TCA cycle?

A

Isocitrate to Alpha-ketoglutarate

27
Q

What enzyme catalyzes Alpha-ketoglutarate to succinyl CoA?

A

Alpha-ketoglutarate dehydrogenase

28
Q

What step yields a high energy phopho-transfer compound (GTP,ATP)?

A

Succinyl CoA to Succinate

29
Q

What enzyme completes the rxn between Succinyl CoA and Succinate?

A

Succinyl CoA synthetase

30
Q

What enzyme catalyzes formation of furmate while generating FADH2?

A

Succinte dehydrogenase

31
Q

FADH2 is not actually released from the enzyme, but electrons are passed directly to ______ in the _____ ______ ______.

A

Co-Q

electron transport chain

32
Q

What enzyme is directly associated with the ETC (complex-II) located in the inner mitochondrial membrane?

A

Succinate dehydrogenase

33
Q

What Catalyzes the hydration of Fumarate to form L-Malate?

A

Fumarase

34
Q

what enzyme oxidizes malate to form oxaloacetate?

A

Malate dehydrogenase

35
Q

The final step of the TCA L-malate to Oxaloacetate is driven by the use of what 2 products?

A
  • Oxaloacetate-citrate synthase

* NADH- electron transport chain

36
Q

High _____ _____ directly inhibits PDH complex subunits E2

A

Acetyl CoA

37
Q

What dictates PDH complex activity?

A

Energy charge of the cell

38
Q

What are the 3 control site of TCA regulation

A
  1. Citrate synthase
  2. Isocitrate dehydrogenase
  3. alpha - ketogluturate dehydrogenase
39
Q

What complex is very similar to PDH?

A

Alpha - ketogluturate dehydrogenase

40
Q

What are the 2 major anaplerotic reactions?

A
  1. Degradation of amino acids

2. Carboxylation of Pyruvate

41
Q

What can stimulate FA synthesis by activating phosphatases and increasing conversion of pyruvate to acetyl CoA?

A

Insulin

42
Q

Allosteric activators of Pyruvate dehydogenase complex via activation of PDP

A

Ca, Mg

43
Q

PDC activators via Inhibition of PDK

A

ADP,CoA,NAD, pyruvate

44
Q

Inhibitors of PDC via allosteric activation of PDK?

A

Acetyl CoA, NADH

45
Q

Inhibitors of PDC via PDK activation

A

Acetyl CoA, ATP

46
Q

What does Arsenite do?

A

Inhibits PDC by binding to lipoic acid in E2

47
Q

Anaplerotic reactions are required during state of _____ energy.

A

Low

Biochem test 3 (11 decks)

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