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Biochemistry Exam 2 > Chapter 19: Harvesting Electrons from the Cycle > Flashcards

Chapter 19: Harvesting Electrons from the Cycle Flashcards

1
Q

The citric acid cycle is the final common pathway for…

A

The oxidation of fuel molecules

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2
Q

The citric acid cycle oxidizes ______ to ______.

A

Acetyl CoA to CO2

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3
Q

The function of the citric acid cycle is to __________ from carbon fuels in form of NADH and FADH2

A

Harvest high-energy electrons

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4
Q

The citric acid cycle is strictly….

A

Aerobic

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5
Q

Citric acid cycle consists of 2 stages:

A
  1. Oxidation of the 2 carbon atoms to 2 CO2
  2. Regeneration of oxaloacetate.
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6
Q

Both stages of the citric acid cycle generate…

A

High-energy electrons that are used in oxidative phosphorylation.

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7
Q

Stage1 of Citric Acid Cycle:

A

Acetyl CoA + Oxaloacetate –> Citryl CoA (Int) –> Citrate

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8
Q

Citrate synthase exhibits…

A

Induced fit

*Leads to formation of the binding site for acetyl CoA

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9
Q

Step 2 of Citric Acid Cycle:

A

Citrate –> cis-Aconitate (Int) –> Isocitrate

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10
Q

_______ catalyzes the formation of isocitrate from citrate

A

Aconitase

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11
Q

Step 3 of Citric Acid Cycle

A

Isocitrate –> Oxalosuccinate (unstable int) –> a-Ketoglutarate

*First reaction where CO2 and NADH produced

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12
Q

_________ catalyzes the oxidative decarboxylation of isocitrate to a-ketoglutarate

A

Isocitrate dehydrogenase

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13
Q

Step 4 of Citric Acid Cycle

A

a-Ketoglutarate –> Succinyl CoA

*Produces CO2 and NADH

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14
Q

_________ catalyzes the formation of succinyl CoA by oxidative decarboxylation of a-ketoglutarate.

A

a-ketoglutarate dehydrogenase complex

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15
Q

Stage 2: Step 5 of Citric Acid Cycle

A

Succinyl CoA –> Succinate + GTP

*High phosphoryl potential

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16
Q

_______ catalyzes the cleavage of succinyl CoA to form succinate and GTP.

A

Succinyl CoA synthetase

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17
Q

Step 6 of Citric Acid Cycle

A

Succinate –> Fumarate

by succinate dehydrogenase

*produces FADH2

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18
Q

Step 7 of Citric Acid Cycle

A

Fumarate –> Malate

by fumarase

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19
Q

Step 8 of Citric Acid Cycle

A

Malate –> Oxaloacetate + NADH

by malate dehydrogenase

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20
Q

The citric acid cycle produces

A
  • High-transfer potential electrons
  • GTP
  • CO2
21
Q

The NADH and FADH2 formed in the citric acid cycle are oxidized by…

A

The electron transport chain

22
Q

How many ATP generated per NADH? per FADH2?

A
  1. 5 ATP per NADH
  2. 5 ATP per FADH2
23
Q

1 Acetyl unit generates _____ molecules of ATP.

A

10

24
Q

Citric acid cycle is the __________ for aerobic oxidation of fuel molecules and is a source of _______.

A

Final common pathway; building blocks

25
Q

The key control points in the citric acid cycle are the reactions catalyzed by…

A

Isocitrate dehydrogenase and α-ketoglutarate dehydrogenase.

26
Q

Control Point 1: Isocitrate dehydrogenase is allosterically activated by ____ and inhibited by ____.

A

Activated by ADP

Inhibited by NADH and ATP

27
Q

Control Point 2: a-Ketoglutarate dehydrogenase is inhibited by _______.

A
  • Succinyl CoA
  • NADH
  • ATP
28
Q

Rate of citric acid cycle is reduced when the cell has…

A

High levels of ATP and NADH.

29
Q

Many of the components of the citric acid cycle are…

A

Precursors for biosynthesis of key biomolecules.

30
Q

Intermediates of the Citric Acid Cycle must be replinished. Replenishing reactions are called…

A

Anaplerotic reactions.

31
Q

An example of anaplerotic reaction is the carboxylation of…

A

Pyruvate by pyruvate carboxylase

32
Q

Defects in succinate dehydrogenase, fumarase or pyruvate dehydrogenase kinase can contribute to the development of _____.

A

Cancer

33
Q

These defects contribute to use of aerobic glycolysis (Warburg effect) by cancer cells leading to production of _____.

A

Lactate

34
Q

The glyoxylate cycle is similar to the citric acid cycle but bypasses the _________, allowing the synthesis of carbohydrates from fats.

A

Two decarboxylation steps

35
Q

The glyoxylate cycle has two specific enzymes that are not present in the citric acid cycle:

A

Isocitrate lyase
Malate synthase

36
Q

The glyoxylate cycle has 2 acetyl CoA enter per cycle and leave as _____.

A

Succinate

(Which can then be converted to glucose)

37
Q

During the Citric Acid Cycle ATP or GTP is produced in the conversion of:

A

Succinyl CoA to Succinate

38
Q

Which enzyme is NOT found in the Glyoxylate Cycle?

  • Aconitase
  • Citrate synthase
  • Isocitrate lyase
  • Malate synthase
  • Isocitrate dehydrogenase
A

Isocitrate dehydrogenase

39
Q

Which citric acid cycle enzyme catalyzes the production of GTP?

A

Succinyl-CoA synthetase

40
Q

Which enzyme converts citrate to isocitrate?

A

Aconitase

41
Q

Which enzyme catalyzes the first oxidative decarboxylation reaction in the citric acid cycle and produces CO2?

A

Isocitrate dehydrogenase

42
Q

Which compound inhibits the pyruvate dehydrogenase complex when present at high concentrations?

  • Pyruvate
  • NADH
  • Fructose 2,6-bisphosphate
  • AMP
  • HS-CoA
A

NADH

43
Q

Which citric acid cycle enzyme catalyzes the production of FADH2?

A

Succinate dehydrogenase

44
Q

In the citric acid cycle, the first NADH is synthesized by the ________________reaction.

A

Isocitrate dehydrogenase

45
Q

T or F: The purpose of the citric acid cycle is to convert acetyl CoA to fatty acids.

A

False

46
Q

T or F: The rate of the citric acid cycle is reduced when the cell has high levels of NADH.

A

True

47
Q

In the citric acid cycle, GDP is phosphorylated to GTP during the conversion of ________________ to ________________.

A

Succinyl CoA to Succinate

48
Q

Which citric acid cycle enzyme catalyzes the production of GTP or ATP?

A

Succinyl CoA Synthetase

49
Q

T or F: During the citric acid cycle FADH2 is produced by the enzymatic reaction catalyzed by fumarase.

A

False

Biochemistry Exam 2 (10 decks)

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