TCA

Question 1

Where does the citric acid cycle take place?

Answer 1

In the mitochondrial matrix

Question 2

What is the rate-limiting enzyme of the citric acid cycle?

Answer 2

Isocitrate Dehydrogenase

Question 2

What are the three key regulatory enzymes of the TCA cycle?

Answer 2

Citrate Synthase, Isocitrate Dehydrogenase, α-Ketoglutarate Dehydrogenase

Question 3

What is the net ATP yield per turn of the TCA cycle?

Answer 3

12 ATP per Acetyl-CoA (24 ATP per glucose)

Question 4

What are the products of one TCA cycle turn?

Answer 4

3 NADH, 1 FADH₂, 1 GTP (→ ATP), 2 CO₂

Question 5

What amino acids can enter the TCA cycle as α-Ketoglutarate?

Answer 5

Glutamate, Glutamine, Proline, Arginine, Histidine

Question 6

What TCA intermediate is used for heme synthesis?

Answer 6

Succinyl-CoA

Question 7

What is the function of anaplerotic reactions in the TCA cycle?

Answer 7

Replenish intermediates lost to biosynthesis (e.g., Pyruvate → Oxaloacetate by Pyruvate Carboxylase)

Question 8

What is the first step of the TCA cycle?
A) Isocitrate → α-Ketoglutarate
B) Citrate → Isocitrate
C) Acetyl-CoA + Oxaloacetate → Citrate
D) Succinate → Fumarate

Answer 8

C) Acetyl-CoA + Oxaloacetate → Citrate

Question 9

What enzyme converts Succinate to Fumarate?
A) Isocitrate Dehydrogenase
B) α-Ketoglutarate Dehydrogenase
C) Succinate Dehydrogenase
D) Citrate Synthase

Answer 9

C) Succinate Dehydrogenase

Question 10

Which of the following inhibits the TCA cycle?
A) High ADP
B) High ATP
C) Low NADH
D) High Pyruvate

Answer 10

B) High ATP

Question 11

Which amino acids can be converted into Oxaloacetate?
A) Valine & Methionine
B) Aspartate & Asparagine
C) Phenylalanine & Tyrosine
D) Arginine & Histidine

Answer 11

B) Aspartate & Asparagine

Question 12

Which TCA intermediate is used in gluconeogenesis?
A) Succinyl-CoA
B) Fumarate
C) Oxaloacetate
D) Malate

Answer 12

C) Oxaloacetate