Carbs 5

Question 1

What is the name of the product oxidized from pyruvate & enters the CAC & what enzyme catalyzes this reaction ?

Answer 1

Acetyl-CoA & Pyruvate Dehydrogenase

Question 2

What is the structure of the enzyme Pyruvate Dehydrogenase ?

Answer 2

It is a large enzyme which contains 10 of each type of sub-unit (E1, E2 & E3)

Question 3

What are the functions of each enzyme sub-unit in Pyruvate Dehydrogenase ?

Answer 3

E1: Catalyses the decarboxylation of pyruvate (Pyruvate Dehydrogenase)
E2: Transfers the acetyl group to Co-enzyme A (Dihydrolipoyl Transacetylase)
E3: recycles the lipoyllysine through the reduction of FAD (FAD -> FADH2), which is recycled by passing electrons to NAD+ (NAD -> NADH + H) (Dihydrolipoyl Dehydrogenase)

Question 4

With each turn of the CAC how many carbons enter ?

Answer 4

2 Carbons

Question 5

How many carbons in total are lost through the CAC and what products do they leave as ?

Answer 5

2 Carbons (CO2)

Question 6

What is the molar density of CO2 ?

Answer 6

0.05 mol/L

Question 7

If a cell has enough energy what regulates Pyruvate Dehydrogenase ?

Answer 7

Its immediate products : NADH, Acetyl-CoA & ATP.

Question 8

If a cell is lacking energy what regulates Pyruvate Dehydrogenase ?

Answer 8

Pyruvate & ADP (switches the enzyme on, positively regulates)

Question 9

What are the two main points of regulation within the CAC & are they reversible ?

Answer 9

1: Isocitrate -> Alpha-Ketogluterate (Isocitrate Dehydrogenase) ATP & NADH turns off Enzyme.
ADP turns on enzyme.
2: Alpha-Ketogluterate -> Succinyl-CoA (Ketogluterate Dehydrogenase) ATP, NADH & Succinyl-CoA turns enzyme off.