12 Link reaction & Krebs cycle

  • Created by: lee8444
  • Created on: 15-03-20 17:01

The link reaction

  • Pyruvate is produced during glycolysis in the cytoplasm
  • Pyruvate is then actively transported into the matrix of the mitochondria

Main steps

  • Pyruvate is oxidised into acetate
    • 3-carbon pyruvate loses a carbon dioxide molecule and two hydrogens
    • The hydrogens are accepted by NAD which forms reduced NAD which can later be used during oxidative phosphorylation
  • The two-carbon acetate combines with coenzyme A (CoA) - this produces acetylcoenzyme A

Pyruvate + NAD + CoA --> acetyl CoA + reduced NAD + CO2

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The Krebs Cycle

  • Series of oxidation-reduction reactions
  • 1) The 2-carbon acetylcoenzyme A combines with 4-carbon oxaloacetate making a 6-carbon molecule
  • 2) In a series of reactions, the 6-carbon molecule loses 2 carbon dioxide molecules and some hydrogen to produce oxaloacetate and a single ATP molecule (substrate-level phosphorylation)
  • Coenzymes
    • not actually enzymes
    • they are molecules that enzymes need to function
    • they carry hydrogen atoms from one molecule to another
    • NAD, FAD, NADP
  • Significance
    • breaks down macromolecules - pyruvate into carbon dioxide
    • produces reduced coenzymes
    • regenerates oxaloacetate
    • it is a source of intermediate compounds such as fatty acids, amino acids and chlorophyll
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