Krebs

Question 1

Where does the citric acid cycle take place? Is it catabolic or anabolic?

Answer 1

Mitochondrial matrix, both

Question 2

Pyruvate fates?

Answer 2

Lactic acid (needs niacin)
Acetyl CoA (niacin, pantothenic acid, riboflavin, lipoic acid, thiamine)
Alanine (B6)
Oxaloacetate (biotin)

Question 3

CoA from pyruvate isn’t part of krebs. Major way to make it though. What is the enzyme that does this?

Answer 3

Pyruvate dehydrogenase. Irreversible. Produces CoA and CO2 and NADH

Question 4

Pyruvate dehydrogenase parts

Answer 4

E1 (bound to thiamine)
E2 (bound to lipoic acid)
E3 (bound to riboflavin/FAD)

Question 5

PDH regulation
Inhibited by?
Promoted by?

Answer 5

Inhibited by Acetyl CoA and NADH. Covalently inhibited by PDH kinase(cAMP independent). Promoted by norepinephrine and insulin

Question 6

PDH deficiency

Answer 6

X linked. Severe neuro and acidosis in males, not in females.

Question 7

Deficiency in E2

Answer 7

Primary biliary cirrhosis. Bilirubin, cholesterol up, and bile acids. Cholestasis. Autoimmune

Question 8

Enzyme of step 1 in krebs

Answer 8

Citrate synthase. Inhibited by citrate

Question 9

Enzyme of step three in krebs

Answer 9

Isocitrate dehydrogenase. Makes CO2, NADH

Question 10

Step 4 enzyme in krebs

Answer 10

Alpha ketoglutarate dehydrogenase. Makes CO2 and NADH. Similar to PDH

Question 11

Step 5 krebs enzyme

Answer 11

Succinyl CoA synthetase. Makes GTP

Question 12

Step 6 krebs enzyme

Answer 12

Succinate dehydrogenase. Makes FADH2. Inhibited by malonate

Question 13

Step 8 krebs enzyme

Answer 13

Malate dehydrogenase. Makes NADH

Question 14

Krebs steps producing CO2

Answer 14

3 and 4

Question 15

Krebs steps producing GTP

Answer 15

5

Question 16

Krebs steps producing NADH

Answer 16

3,4,8

Question 17

Can fatty acids with even number of carbons generate acetyl CoA?

Answer 17

No, must be odd. Fat cannot provide energy to brain as well. Propionyl CoA produced from odd number