1.4.5 The link reaction and Krebs cycle

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  • Created by: JTY3
  • Created on: 20-04-16 14:12
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  • The link reaction
    • Pyruvate dehydrogenase removes hydrogen atoms from pyruvate.
    • Pyruvate decarboxylase removes a carboxyl group, which eventually becomes CO2, from pyruvate.
    • The coenzyme NAD accepts the hydrogen atoms
    • Coenzyme A (CoA) accepts acetate, to become acetyl coenzyme A. CoA carrys acetate to the krebs cycle
    • 2 pyruvate + 2NAD + 2CoA > 2CO2 + 2 reducedNAD +2 acetyle CoA
      • No ATP is produced
  • The Krebs cycle
    • The Krebs cycle takes place in the mitochondrial matrix .
      • It is series of enzyme-catalysed reactions that oxidise the acetyl group of acetyl CoA to 2 molecules of CO2.
        • It also produces 1 ATP by substrate level phosphorylation
          • Reduces 3 NAD
            • potential to produce more ATP in oxidative phosphorylation
              • Reduces 1 FAD
          • Reduces 1 FAD
    • 1. Acetate is offloaded from coenzyme A  and joins with a 4C compound called oxaloacetate to form citrate 6C
      • 2. Citrate is decarboxylated and dehydrogenated to form a 5C compound.
        • The 2 H are accepted by 1 NAD which becomes reduced.
        • 3. The 5C compound is decarboxylated and dehydrogenated to form a 4C compound
          • Another reduced NAD is formed.
          • 4. 4C is changed into another 4C during which an ADP is phosphorylated to form ATP
            • 5. The second 4C is changed into another 4C.
              • 2 H atoms are accepted by FAD to make reduced FAD.
              • 6. The third 4C is further dehydrogenated and regenerates oxaloacetate
                • Another NAD is reduced.
    • Products of the Krebs cycle.
      • 6 reduced NAD
      • 2 reduced FAD
      • 4 CO2
      • 2 ATP
    • Although oxygen isn't used in these stages of respiration, they wont occur in its absence.
      • The link reaction
        • Pyruvate dehydrogenase removes hydrogen atoms from pyruvate.
        • Pyruvate decarboxylase removes a carboxyl group, which eventually becomes CO2, from pyruvate.
        • The coenzyme NAD accepts the hydrogen atoms
        • Coenzyme A (CoA) accepts acetate, to become acetyl coenzyme A. CoA carrys acetate to the krebs cycle
        • 2 pyruvate + 2NAD + 2CoA > 2CO2 + 2 reducedNAD +2 acetyle CoA
          • No ATP is produced

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