Step of kerb cycle

Step 1

Acetyl Co-A combines with a four-carbon compound, oxaloacetate, and releases the CoA group resulting in a six-carbon molecule called citrate.

Step 2

In the second step, citrate gets converted to isocitrate, an isomer of citrate. This is a two-step process. Citrate first loses a water molecule and then gains one to form isocitrate.

Step 3

The third step involves oxidation of isocitrate. A molecule of carbon dioxide is released leaving behind a five-carbon molecule, ɑ-ketoglutarate. NAD⁺ gets reduced to NADH. The entire process is catalyzed by the enzyme isocitrate dehydrogenase.

Step 4

Here, ɑ-ketoglutarate is oxidized reducing NAD⁺ to NADH and releasing a molecule of carbon dioxide.

CoA is picked up by the remaining four-carbon molecules forming an unstable compound succinyl CoA. ɑ-ketoglutarate dehydrogenase catalyzes the entire process.

Step 5

CoA from succinyl CoA is replaced with a phosphate group. It is then transferred to ADP to make ATP. Succinate, a four-carbon molecule is produced in this step.

Step 6

Succinate is oxidized to fumarate. Two hydrogen atoms are transferred to FAD to produce FADH₂. FADH₂ transfers its electrons directly to the electron transport chain since the enzyme carrying out the reaction is embedded in the inner membrane of mitochondria.

Step 7

A water molecule is added to fumarate which is then converted to malate.

Step 8

The oxidation of malate regenerates oxaloacetate, a four-carbon compound, and another molecule of NAD⁺ is reduced to NADH in this step.