Citric Acid Cycle

1
Citric Acid Cycle

• Or
• Krebs cycle or
• TCA cycle

2
Evidence for the Cycle or Following Isotopes
through the cycle

• Succinate Malate and a-Ketoglutarate oxidized in
  tissue
• Addition of succinate, fumarate, malate,
  oxaloacetate, catalytically activates
  respiration. Szent-Gryögyi- Nobel prize 1937
• a-ketoglutarate converted to succinate in muscle
• Citrate converted to isocitrate and
  a-ketoglutarate -Martius, Knoop-
• Succinate formed from fumarate, malate or
  oxaloacetate. -Krebs-
• Pyruvate and oxaloacetate ? Citrate CO2Suggests
  the Closing of the cycle. -Krebs-
• Acyl-CoA discovered in 1945 -Kaplan, Lipmann-
• Nobel prize to Krebs and Lipmann in 1953

3
Problems To think about Chap 21

• 1,3,4,7,8,9,11,12,14

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24 E2 subunits 24 E1 orange
a and b together
12 E3 Red
8
Lipoamide
Dihydrolipoamide
9
Decarboxylation

• TPP again acting as electron sink

10
Citrate synthase

• Claisen Condensation
• Variation of Aldol condensation.