The Krebs Cycle (Citric Acid Cycle)

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The Krebs Cycle(Citric Acid Cycle)

• By Zuzana Kollarova

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Krebs Cycle

• Enzymes in the matrix of the mitochondria
  catalyze a cycle of reactions called the Krebs
  cycle.
• The common pathway to completely oxidize fuel
  molecules which mostly is acetyl CoA ,the product
  from the oxidative decarboxylation of pyruvate
• It enters the cycle and passes ten steps of
  reactions that yield energy and CO2
• These reactions can only occur if oxygen is
  available and so are part aerobic cell
  respiration
• Prokaryotic cells occurs in the cytoplasm
• Eukaryotic cells occurs in the mitochondria

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Steps

1. In the first reaction of the cycle an acetyl
   group is transferred from acetyl CoA to a
   four-carbon compound (oxyloacetate) to form a
   six-carbon compound (Citrate).
2. Citrate is converted to isocitrate.
3. The 6-carbon isocitrate is oxidized by NAD to
   produce reduced NADH and 5-carbon
   alpha-ketoglutarate. One carbon is lost as CO2
   (decarboxylation). CO2 is waste product.
4. The 5-carbon alpha-ketoglutarate is oxidized by
   NAD to produce reduced NADH and 4-carbon
   succinyl-CoA. (One carbon is lost as CO2.)

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• 5. Hydrogen is removed Oxidation of
  succinyl-CoA produces succinate and one GTP that
  is converted to ATP. Oxidation reactions release
  energy, much of which is stored by the carriers
  when they accept hydrogen.
• 6. Oxidation of succinate by FAD produces reduced
  FADH2 and fumarate.
• Fumarate is converted into malate
• Oxidation of malate by NAD produces reduced NADH
  and oxaloacetate

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• Animation http//www.youtube.com/watch?vaCypoN3X
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