L7 Citric Acid Cycle

Question 1

What are the three stages of cellular respiration?

Answer 1

(1) Acetyl-CoA production
(2) Acetyl-CoA oxidation
—-Citric acid cycle/ Tricarboxylic acid cycle/ Kreb cycle
(3) Electron transfer and oxidative phosphorylation

Question 2

What are the reduced e- carriers?

Answer 2

NADH and FADH2

Question 3

Which stage generates H2O?

Answer 3

Electron transfer and oxidative phosphorylation

Question 4

Where does the transformation of acetyl-CoA from pyruvate occurs?

Answer 4

Inside mitochondria’s matrix

Question 5

The enzyme complex responsible for transforming pyruvate to acetyl-CoA have how many components?

Answer 5

3

Question 6

What is the overall feature of transforming acetyl-CoA from pyruvate?

Answer 6

Oxidative decarboxylation

Question 7

What are the 5 cofactors involved in the transformation of acetyl-CoA from pyruvate?

Answer 7

(1) Thiamine pyrophosphate (TPP)
(2) Lipoic acid
(3) Coenzyme A
(4) Flavin adenine dinucleotide (FAD)
(5) Nicotinamide adenine dinucleotide (NAD+)

Question 8

What is E1 in the enzyme complex called?

Answer 8

Pyruvate dehydrogenase

Question 9

What are the two reactions that E1 catalyzes?

Answer 9

(1) Decarboxylation of pyruvate
(2) Transfer of acetyl group to lipoamide, which is a prosthetic group in E2

Question 10

What is E2 in the enzyme complex called?

Answer 10

Dihydrolipoamide acetyltransferase

Question 11

What is the reaction that E2 catalyzes?

Answer 11

Transfer of acetyl group to co-enzyme

Question 12

When Arsenite (As) poisoning occurs, which component of the enzyme complex is inhibited?

Answer 12

E2

Question 13

What is E3 in the enzyme complex called?

Answer 13

Dihydrolipoamide dehydrogenase

Question 14

What are the two reactions that E3 catalyzes?

Answer 14

(1) Regeneration of lipoamide (oxidized form)
(2) Regeneration of FAD

Question 15

Which two components of the enzyme complex are affected by the product inhibition and substrate activation?

Answer 15

E2 and E3

Question 16

By which process is subunit E1 is regulated?

Answer 16

Phosphorylation

Question 17

alpha- Ketoglutarate dehydrogenase complex resembles which enzyme in both structure and function?

Answer 17

Pyruvate dehydrogenase complex

Question 18

What are the similarity and differences between Synthetases and Synthase?

Answer 18

Similarity: Both types of enzymes are involved in joining substrates together

Differences:
(1) Synthase reactions do not require NTP (nucleotide triphosphates)
(2) Synthetase reactions use NTP (ATP or GTP) as energy source

Question 19

What is the strong inhibitor of succinate dehydrogenase?

Answer 19

Malonate, which is structurally similar to succinate

Question 20

How many ATP equivalents are generated in one TCA cycle?

Answer 20

10

Question 21

2 NADH can result in how many ATP in the following electron transport chain process?

Answer 21

5 ATP

Question 22

2 FADH2 can result in how many ATP in the following electron transport chain process?

Answer 22

3 ATP

Question 23

What is the net profit of aerobic degradation of glucose?

Answer 23

32 ATP

Question 24

What are the four enzymes that are mainly being regulated in the citric acid cycle?

Answer 24

(1) Pyruvate dehydrogenase complex
(2) Citrate synthase
(3) Isocitrate dehydrogenase
(4) alpha-ketoglutarate dehydrogenase