Lecture 11 - TCA Cycle

Question 1

Which intermediate of the TCA cycle provides the carbon skeleton to produce a heme product?

A. Oxaloacetate
B. Citrate
C. Succinyl-CoA
D. a-ketoacids (OAA, a-KG)

Answer 1

C

Question 2

Which intermediate of the TCA cycle provides the carbon skeleton to produce glucose?

A. Oxaloacetate
B. Citrate
C. Succinyl-CoA
D. a-ketoacids (OAA, a-KG)

Answer 2

A

Question 3

Which intermediate of the TCA cycle provides the carbon skeleton to produce fatty acids?

A. Oxaloacetate
B. Citrate
C. Succinyl-CoA
D. a-ketoacids (OAA, a-KG)

Answer 3

B

Question 4

Which intermediate of the TCA cycle provides the carbon skeleton to produce amino acids and nucleotides?

A. Oxaloacetate
B. Citrate
C. Succinyl-CoA
D. a-ketoacids (OAA, a-KG)

Answer 4

D

Question 5

12 molecules of ATP are produced per TCA cycle. 9 ATP come from the __________.

A. GTP
B. FADH2
C. NADH
D. CO2

Answer 5

C (3 NADH produced/cycle)

Question 6

12 molecules of ATP are produced per TCA cycle. 2 ATP come from the __________.

A. GTP
B. FADH2
C. NADH
D. CO2

Answer 6

B

Question 7

12 molecules of ATP are produced per TCA cycle. 1 ATP comes from the __________.

A. GTP
B. FADH2
C. NADH
D. CO2

Answer 7

A

Question 8

The rate-limiting step in the TCA cycle is catalyzed by __________.

Answer 8

isocitrate dehydrogenase

Question 9

Citrate serves as a ______ allosteric regulator for phosphofructokinase-1 (glycolysis).

Answer 9

negative

Question 10

Citrate serves as a positive allosteric regulator for ______________.

Answer 10

CoA carboxylase (fatty acid synthesis)

Question 11

Reactions which replace intermediates in the TCA cycle are known as ___________.

Answer 11

anaplerotic reactions

Question 12

The supply of oxidized cofactors (NAD+ and FAD) in the TCA cycle is dependent on:

Answer 12

the rate of respiration - which is dependent on the availability of O2 and ADP

Question 13

Which is NOT an enzyme that catalyzes a TCA cycle reaction in which CO2 is lost?

A. PDH complex
B. Succinate DH
C. Isocitrate DH
D. a-ketogluterate DH

Answer 13

B. Succinate catalyzes a reaction in which FADH2 is formed.

Question 14

Which is an enzyme that catalyzes a TCA cycle reaction in which FADH2 is formed?

A. PDH complex
B. Succinate DH
C. Isocitrate DH
D. a-ketogluterate DH
E. Succinate thiokinase

Answer 14

B

Question 15

Which is an enzyme that catalyzes a TCA cycle reaction in which substrate-level phosphorylation occurs?

A. PDH complex
B. Succinate DH
C. Isocitrate DH
D. a-ketogluterate DH
E. Succinate thiokinase

Answer 15

E

Question 16

Which is NOT an enzyme that catalyzes a TCA cycle reaction in which NADH is formed?

A. PDH complex (before TCA cycle)
B. Succinate DH
C. Isocitrate DH
D. Malate DH
E. All of these catalyze reactions in which NADH is formed.

Answer 16

E

Question 17

Isocitrate dehydrogenase is allosterically inhibited by _____.

Answer 17

ATP

Question 18

Isocitrate dehydrogenase is allosterically inhibited by _____.

Answer 18

ADP

Question 19

In what type of energy state would citrate accumulate in the cell?

Answer 19

High energy state - indicated by ATP and NADH, which allosterically inhibit isocitrate DH

Question 20

Two compounds that link the citric acid cycle with the respiratory chain (ETC) are:

Answer 20

1. NADH

2. FADH2