Krebs cycle
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The Krebs cycle is a part of cellular respiration. It comes after the Link reaction and provides the hydrogen and electrons needed for the Electron transport chain. It happens in the cytoplasm of mitochondria.
Acetyl CoA, a compound made of 2 carbon molecules, is formed by glycolysis and the Link reaction. It joins to a 4-carbon compound giving a 6-carbon compound. The 6-carbon compound loses a molecule of carbon dioxide (called decarboxylation) and 2 hydrogen molecules (called dehydrogenation). This gives a 5-carbon compound. The hydrogen removed joins to a molecule of NAD+ found in the cytoplasm of the mitochondria to form NADH, and the carbon dioxide simply diffuses out of the mitochondria as waste.
The 5-carbon compound now has 1 more carbon dioxide molecule removed and 3 hydrogen molecules removed. Two of these hydrogen molecules are joined to NAD+, one is joined to another FAD+). ATP is produced by substrate level phosphorylation.
The 4-carbon compound cycles back to the beginning to be re-joined to Acetyl CoA. The Krebs cycle happens as two separate cycles, as two molecules of pyruvate are made by glycolysis.
[change] Summary
- Two molecules of carbon dioxide are given off
- One molecule of ATP is formed
- Three molecules of NAD+ are combines with hydrogen (NAD+ → NADH)
- One molecule of FAD+ combines with hydrogen (FAD+ → FADH)
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