Citric Acid Cycle

Question 1

Where does the TCA cycle occur?

Answer 1

Mitochondrial matrix

Question 2

Which of the compounds below are the products of the oxidation of acetyl CoA in the citric acid cycle?

A. Oxaloacetate and NAD
B. GTP and Acetyl CoA
C. NADH, FADH2 and CO2
D. Water, CO2 and ATP

Answer 2

C

Question 3

How many high-energy phosphates (ATP) can be obtained from the over-all reaction:

Isocitrate — > —– > —— > Fumarate + 2CO2 + 2 H2O

A. 7
B. 8
C. 9
D. 10

Answer 3

C

Question 4

Which is true of TCA cycle?

a. It produces reducing equivalents for\ETC
b. Has anabolic and catabolic phases
c. It is the final common pathway for the metabolism of glucose, fatty acid and amino acids
d. All of the above

Answer 4

D

Question 5

Before pyruvate can enter the TCA, it must be converted to acetyl acid. Which enzyme catalyzes this reaction?

Answer 5

Pyruvate dehydrogenase

Question 6

Pyruvate dehydrogenase required five coenzymes. Which are they?

Answer 6

TPP, FAD, CoA, NAD, lipoate

Question 7

Which molecules undergo condensation to form citrate?

Answer 7

Oxaloacetate and acetyl CoA

Question 8

Which enzyme catalyzes the formation of citrate?

Answer 8

Citrate synthase

Question 9

Which enzyme catalzes the conversion of isocitrate to α-ketoglutarate?

Answer 9

Isocitrate dehydrogenase

Question 10

Which enzyme catalyzes conversion of α -ketoglutarate to succinyl-CoA?

Answer 10

α -ketoglutarate dehydrogenase

Question 11

Which enzymes of the TCA produce carbon dioxide?

Answer 11

Isocitrate dehydrogenase and α -ketoglutarate dehydrogenase

Question 12

Which enzymes need NAD+ as electron acceptor?

Answer 12

Isocitrate dehydrogenase, α -ketoglutarate dehydrogenase and L-malate dehydrogenase

Question 13

Which enzyme of the TCA closely resembles the PDH complex in both structure and function?

Answer 13

α -ketoglutarate dehydrogenase

Question 14

Which cofactors does α -ketoglutarate dehydrogenase require?

Answer 14

NAD, FAD, TPP, lipoate, CoA

Question 15

PDH complex and α -ketoglutarate dehydrogenase complex are each made up of how many enzymes?

Answer 15

3

Question 16

Which enzyme catalyzes the conversion of succinyl-CoA to succinate?

Answer 16

Succinyl-CoA synthetase/ succinic thiokinase

Question 17

Which enzyme catalyzes the conversion of succinate to fumarate?

Answer 17

Succinate dehydrogenase

Question 18

Which enzyme of the TCA produces GTP /ATP?

Answer 18

Succinyl-CoA synthetase/ succinic thiokinase

Question 19

Which enzyme of the TCA produces FADH2?

Answer 19

Succinate dehydrogenase

Question 20

Which enzyme catalyzes the hydration of fumarate to malate?

Answer 20

Fumarase

Question 21

Which enzyme catalyzes the dehydration of malate to oxaloacetate?

Answer 21

L-malate dehydrogenase

Question 22

What are the products of TCA?

Answer 22

3 NADH, 1 FADH2, 2CO2, 1 ATP (GTP)

Question 23

Oxaloacetate has an extremely low concentration in the cell. T/F

Answer 23

T

Question 24

Citric acid cycle is an amphibolic pathway. What does it mean?

Answer 24

The citric acid cycle serves both catabolic and anabolic processes

Question 25

When the citric acid cycle is deficient in oxaloacetate or any other intermediates, how does the cell produce these intermediates?

Answer 25

Pyruvate is carboxylated to oxaloacetate

Question 26

Pyruvate carboxylase is inactive without which positive allosteric modulator?

Answer 26

Acetyl-CoA

Question 27

PEP is activated by F 1,6-BP. T/F

Answer 27

T

Question 28

Biotin is a specialized carrier of one-carbon groups in their most oxidized form; CO2. T/F

Answer 28

T

Question 29

Succinyl-CoA inhibits which TCA enzymes?

Answer 29

α -ketoglutarate dehydrogenase and citrate synthase

Question 30

Citrate is an allosteric inhibitor of which glycolytic enzyme?

Answer 30

PFK-1