Chapter 19: Harvesting Electrons from the Cycle Flashcards Preview

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

Flashcards in Chapter 19: Harvesting Electrons from the Cycle Deck (49):
1

The citric acid cycle is the final common pathway for...

The oxidation of fuel molecules

2

The citric acid cycle oxidizes ______ to ______.

Acetyl CoA to CO2

3

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

 Harvest high-energy electrons

4

The citric acid cycle is strictly....

Aerobic

5

Citric acid cycle consists of 2 stages:

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

6

Both stages of the citric acid cycle generate...

High-energy electrons that are used in oxidative phosphorylation.

7

Stage1 of Citric Acid Cycle:

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

8

Citrate synthase exhibits...

Induced fit

*Leads to formation of the binding site for acetyl CoA

9

Step 2 of Citric Acid Cycle:

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

10

_______ catalyzes the formation of isocitrate from citrate

Aconitase

11

Step 3 of Citric Acid Cycle

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

*First reaction where CO2 and NADH produced

12

_________ catalyzes the oxidative decarboxylation of isocitrate to a-ketoglutarate

Isocitrate dehydrogenase

13

Step 4 of Citric Acid Cycle

a-Ketoglutarate --> Succinyl CoA

*Produces CO2 and NADH

14

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

a-ketoglutarate dehydrogenase complex

15

Stage 2: Step 5 of Citric Acid Cycle

Succinyl CoA --> Succinate + GTP

*High phosphoryl potential

16

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

Succinyl CoA synthetase

17

Step 6 of Citric Acid Cycle

Succinate --> Fumarate

by succinate dehydrogenase

*produces FADH2

18

Step 7 of Citric Acid Cycle

Fumarate --> Malate 

by fumarase

19

Step 8 of Citric Acid Cycle

Malate --> Oxaloacetate + NADH

by malate dehydrogenase

20

The citric acid cycle produces

  • High-transfer potential electrons
  • GTP
  • CO2

21

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

The electron transport chain

22

How many ATP generated per NADH? per FADH2?

2.5 ATP per NADH

1.5 ATP per FADH2

23

1 Acetyl unit generates _____ molecules of ATP.

10

24

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

Final common pathway; building blocks

25

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

Isocitrate dehydrogenase and α-ketoglutarate dehydrogenase.

26

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

Activated by ADP 

Inhibited by NADH and ATP

27

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

  • Succinyl CoA
  • NADH
  • ATP

28

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

 High levels of ATP and NADH.

29

Many of the components of the citric acid cycle are...

 Precursors for biosynthesis of key biomolecules.

30

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

 Anaplerotic reactions.

31

An example of anaplerotic reaction is the carboxylation of...

Pyruvate by pyruvate carboxylase

32

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

Cancer

33

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

Lactate

34

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

Two decarboxylation steps

35

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

Isocitrate lyase
Malate synthase

36

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

 Succinate

(Which can then be converted to glucose)

37

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

Succinyl CoA to Succinate

38

Which enzyme is NOT found in the Glyoxylate Cycle?

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

Isocitrate dehydrogenase

39

Which citric acid cycle enzyme catalyzes the production of GTP?

Succinyl-CoA synthetase

40

Which enzyme converts citrate to isocitrate?

Aconitase

41

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

Isocitrate dehydrogenase

42

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

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

NADH

43

Which citric acid cycle enzyme catalyzes the production of FADH2?

Succinate dehydrogenase

44

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

Isocitrate dehydrogenase

45

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

False

46

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

True

47

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

Succinyl CoA to Succinate

48

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

Succinyl CoA Synthetase

49

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

False