What happens during the Krebs cycle?

The Krebs cycle, also known as the citric acid cycle, is the second stage of aerobic respiration where acetyl-CoA is completely oxidized to release energy carriers and carbon dioxide.

It takes place in the mitochondrial matrix and plays a key role in generating high-energy molecules for ATP production.

Steps involved in the Krebs cycle:

1. Formation of citric acid
Acetyl-CoA (2-carbon) combines with oxaloacetate (4-carbon) to form citrate (6-carbon).

2. Oxidation and decarboxylation
Citrate undergoes a series of reactions:

• Two molecules of carbon dioxide (CO₂) are released

• High-energy electrons are transferred to NAD⁺ and FAD, forming NADH and FADH₂

3. Regeneration of oxaloacetate
After multiple steps, the 4-carbon oxaloacetate is regenerated, allowing the cycle to continue.

Energy produced (per glucose molecule):

• 2 ATP (or GTP)

• 6 NADH

• 2 FADH₂

• 4 CO₂ (as waste)

Role in respiration:

• Provides electron carriers (NADH, FADH₂) for the electron transport chain

• Completes the breakdown of glucose-derived molecules

Importance:

• Central pathway in cellular respiration

• Links carbohydrate, fat, and protein metabolism

In simple terms: The Krebs cycle breaks down acetyl-CoA, releases carbon dioxide, and produces energy carriers used to generate ATP.