Krebs Cycle

Question 1

What happens in the Krebs cycle?

Answer 1

Happens in the matrix
Made of enzyme catalysed reactions which oxidises acetylcoenzyme A to 2 molecules of carbon dioxide (per acetylCoA) and releases ATP

Question 2

What happens to the acetyl group?

Answer 2

Acetyl group is released from acetyl CoA.
The group is then added to a 4CARBON oxaloacetate, producing CITRATE

Question 3

How are 6 reduced NAD produced?

Answer 3

1. Citrate is dehydrogenated and 2 hydrogen atoms are picked up by NAD. This happens again because for every glucose, the kreb’s cycle happens twice.
2. The 2 x 5C compound that dehydrogenated citrate produces is also dehydrogenated/decarboxylated which forms 2 reduced NAD and 2 carbon dioxide molecule. 5C becomes a 4C compound
3. 2 x 4C is dehydrogenated twice and regenerated to produce oxaloacetate. 2 reduced NAD are produced.

2 +2 + 2 = 6 reduced NAD

Question 4

How are 2 reduced FAD produced?

Answer 4

2 x 4C is dehydrogenated the first time and the hydrogen atoms are accepted by 2 FAD coenzymes.

Question 5

How are 2 ATP’s produced?

Answer 5

2x 4C is added to coenzyme A which produces 2x ATP in substrate level phosphorylation.

Question 6

How are 4 CO2 produced?

Answer 6

Citrate is decarboxylated, making 2CO2 molecules
2 x 5C is decarboxylated producing 2 carbon molecules

Question 7

What are the products of Kreb’s cycle?

Answer 7

2 reduced FAD
6 reduced NAD
4 CO2
2 ATP