The Krebs cycle, also called the Citric Acid Cycle or Tricarboxylic Acid (TCA) Cycle, is a key part of cellular respiration — the process by which cells generate energy.
It takes place in the mitochondrial matrix (the inner part of the mitochondria) and operates only when oxygen is available, so it is an aerobic process.
Here’s a explanation of what it does:
- Starting Point:
- The cycle begins with acetyl-CoA, which comes from the breakdown of carbohydrates (from glycolysis), fats (from beta-oxidation), or proteins.
- Acetyl-CoA combines with a molecule called oxaloacetate to form citric acid (citrate) — that’s why it’s called the Citric Acid Cycle.
- Main Function:
- The cycle’s main job is to extract high-energy electrons from acetyl-CoA.
- These electrons are carried by NADH and FADH₂ to the electron transport chain, where most ATP is produced.
- What Happens in the Cycle:
- Citrate goes through a series of reactions, releasing carbon dioxide (CO₂) as a waste product.
- Along the way, NADH and FADH₂ are produced, and a small amount of ATP (or GTP) is directly made.
- In the end, oxaloacetate is regenerated, allowing the cycle to start again.
- Energy Yield (per acetyl-CoA):
- 3 NADH
- 1 FADH₂
- 1 ATP (or GTP)
- 2 CO₂ (waste)
In short:
The Krebs cycle is a series of reactions inside the mitochondria that break down acetyl-CoA to release carbon dioxide and produce NADH and FADH₂, which carry energy to the electron transport chain. It is a central step in energy production, linking carbohydrate, fat, and protein metabolism.