Krebs Cycle

• Pyruvic acid from glycolysis is used to make NADH, ATP, and FADH2 with CO2 as a by-product.
• Occurs in the mitochondria matrix.
• COMPLETELY breaks down the pyruvates.
• Krebs Cycle is an aerobic process even though O2 is not used directly.
• Pyruvic acid is broken down to make acetyl Co-enzyme A (CoA)
• Energy is released which forms NADH and CO2 as waste.
• First part of Krebs Cycle: Inputs: 2 pyruvic acids. Outputs: 2 NADH, 2 CO2, 2 ACETYL CoA.
• Acetyl-CoA adds the 2-carbon acetyl group to a 4-carbon molecule already present, producing 6-carbon molecules called citric acid.
• Citric acid is broken down into a 4-carbon molecule, more CO2 is released and electrons are transferred to energy carriers.
• For every cycle, an ADP molecule converts to an ATP molecule.
• Second Part: Inputs: citric acid. Outputs: 8 NADH, 6 CO2, 2 FADH2, 2 ATP.
• During Krebs Cycle, in 5 places, electron carriers accept a pair of high energy electrons.
• NAD+ -> NADH (Reduction)
• FAD -> FADH2 (Reduction)
• Krebs Cycle is aerobic because while O2 is not directly used, it needs to be present for the reactions to be in the right form. O2 is the final acceptor in the Electron Transport Chain which is closely linked to Krebs Cycle and without oxygen, the Krebs Cycle will not continue efficiently.
• The Krebs Cycle is changed with the addition and removal of water.