Krebs Cycle

• Two acetylcholine A molecules come from the link reaction, so the Krebs cycle occurs twice for each glucose molecule
• Process of the Krebs cycle

  1. Acetylcoenzyme A combines with a 4-carbon compound called oxaloacetate, which releases the coenzyme A
  2. This produces a 6-carbon compound called citrate
  3. In a series of redox reactions, the citrate is converted back to oxaloacetate, producing reduced coenzymes
• Products of the Krebs cycle

  • 2 molecules of carbon dioxide are given out
  • 3 molecules of NAD are reduced
  • 1 molecule of FAD is reduced
• The most important function of the Krebs cycle is the production of the reduced coenzymes that are passed to the electron transport chain
• The production of ATP in the Krebs cycle is known as substrate-level phosphorylation -> phosphate groups are transferred to ADP to form ATP
• Each pyruvate entering the link reaction and Krebs cycle results in:

  • 3 molecules of carbon dioxide
  • 1 molecule of ATP
  • 4 molecules of reduced NAD
  • 1 molecule of reduced NAD

  This is only half of a glucose molecule

  • 2 molecules of ATP and 2 molecules of reduced NAD are also produced in glycolysis
• Total products for one glucose molecule after Krebs cycle:

  • 4 ATP molecules
  • 6 carbon dioxide molecules
  • 10 reduced NAD molecules
  • 2 reduced FAD molecules