Krebs Cycle 6

In this reaction, the Coenzyme A is removed forming succinate. The energy that was stored in the linkage of the CoA to succinate is now used to attach a phosphate to GDP to form GTP. GTP is a close cousin to ATP and the cell has enzymes present that are capable of making an ATP from the energy in the GTP. For this reason, we count the GTP as an ATP on the scorecard. For the purposes of this class, you should count this as an ATP generating reaction. This is not an oxidation reaction so no NADH is formed.


(reactants )

succinyl CoA






succinyl CoA synthetase







Items to note about this reaction:

  1. The removal of the CoA from the succinate releases the stored energy. This energy is used to phosphorylate ADP and form ATP (of course, it is really GDP that is being phosphylated to GTP - we just pretend that ATP is being formed!)
  2. This is the first and only reaction of the Krebs Cycle that produces an ATP. Because the phosphorylation of ADP occurs as a part of the reaction of the substrate, this is referred to as substrate level phosphorylation of ADP.
  3. This reaction is not an oxidation reaction so there is no production of NADH during the reaction.


    after 6 reactions
    ATP Produced NADH Produced FADH Produced CO2 Produced O2 Used
    1 3 0 3 0

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