20 Facts about the Krebs cycle

• Proposed by Hans. A Kreb in 1937
• Occurs in the mitochondria, the power plant of cells
• Takes place after glycolysis, the pyruvates produced travel into the mitochondria of the cell from the cytoplasm
• carbon dioxide is enzymatically removed from each three-carbon pyruvic acid molecule to form acetic acid.  The enzyme then combines the acetic acid with an enzyme, coenzyme A, to produce acetyl coenzyme A, also known as acetyl CoA.
• Acetyl CoA initiates the 8 steps cycle of Krebs cycle
• Acetyl CoA combines with oxaloacetate to form citrate, coenzyme A is ditched and used as a temporary transport.
• An isomerization reaction takes place, forming isocitrate
• NAD oxidizes the isocitrate molecule, forming alpha-ketoglutarate, also releasing CO2 in the process.
• coenzyme A oxidizes the alpha-ketoglutarate molecule to form succinyl-coenzyme A complex.  A molecule of NAD is reduced to form NADH and hydrogen. 
• Coenzyme A is displaced by a free floating phosphate group. The phosphate is transferred to a molecule of ADP to form ATP, leaving behind succinate.
• succinate is oxidized to form fumarate.
• Water is added to the fumarate molecule to form malate.  
• the malate molecule is oxidized to form oxaloacetate, and the Krebs cycle can start all over again.
• For each cycle (1 glucose molecule), 2 molecules of ATP, 6 molecules of NADH, and 2 molecules of FADH2 are produced.
• The NADH and FADH2 molecules will be used to produce ATP in the next step – electron transport chain.
• Hans A. Kreb was awarded the nobel prize for his work
• The availability of oxygen is critical to the ability of the Krebs cycle to function
• The cycle occurs in nearly all aerobic cells, not just in animals.
• The pathway is amphibolic.
• Regulation is provided by substrate availability and product inhibition.