Fates of pyruvate- Lecture 62

Question 1

What is the reaction for pyruvate in yeast?

Answer 1

Pyr –> Acetaldehyde + CO2
Acetaldehyde + NADH –> ethanol + NAD+
Via pyruvate decarboxylase and alcohol dehydrogenase respectively

Question 2

What is the reaction for pyruvate in aerobic cells?

Answer 2

Pyr + NAD+ + CoA –> Acetyl CoA + CO2 + NADH

Question 3

What are the fates of acetyl CoA?

Answer 3

CO2 vai TCA cycle (provides ATP)
Citrate (used for fatty acid synthesis)
Ketone bodies
Cholesterol
Steroids
Acetylation (eg. histones)

Question 4

What are the five isoforms of lactate dehydrogenase?

Answer 4

H4, H3M (brain or heart)
H2M2,
HM3, and M4 (RBC and skeletal muscle)

Question 5

H subunits of LDH have a high affinity for ______, whereas M subunits have a high affinity for _____________.

Answer 5

Lactate and NAD+

Pyruvate and NADH

Question 6

What are the fates of pyruvate?

Answer 6

reduced to lactic acid (lactate)

enter mitochondria for further metabolism to acetyl CoA via pyruvate dehydrogenase

Question 7

What is important about the reaction of pyruvate to lactate in RBCs?

Answer 7

NADH is reoxidize back to NAD+

Question 8

What is contained in the PDH complex?

Answer 8

E1, E2, E3, PDH kinase, PDH phosphatase

Question 9

What vitamin co-factors are involved in the PDH reaction?

Answer 9

TPP (for E1), lipoic acid (E2), riboflavin (E3), phosphopantetheine (CoASH), niacin (NAD+)

Question 10

What are each of the three PDH enzymes inhibited by?

Answer 10

E1: ATP; PDH kinase (hormone control)
E2: acetyl CoA
E3: NADH

Question 11

What is the reaction for pyruvate in RBC, exercising muscles, and embryonic tissues?

Answer 11

Pyr + NADH < —- > lactate + NAD+

Via lactate dehydrogenase