WJEC A2 Biology - Krebs cycle

Acetyl CoA enters the cycle. Combines with a 4 carbon acid to form..

A 6-carbon compound, citrate. CoA regenerated (acetate combined with 4C).

6 carbon acid is de-

dehydrogenated. Making reduced NAD. Also decarboxylated to make CO2 and a 5C acid.

The 5C acid is de-

Dehydrogenated, making reduced NAD and FAD. Decarboxylated to make CO2 and to regenerate the 4C acid back at the start of the cycle. Energy allows Substrate-level phosphorylation giving 1 ATP.

What does dehydrogenation do?

Happens four times. Dehydrogenases remove pairs of hydrogen atoms from the acids. They are collected by hydrogen carriers. NAD’s electrons have a higher energy level so there are 3 reduced NAD molecules and 1 reduced FAD.