Energy and Metabolism

ID #1768

Regarding Glycolysis, we know the first few steps in glycolysis are endergonic, but how do we know when it changes to exergoinc? Also, does Substrate phosphorlation start right after glycolysis and again before the krebs cycle?

     If a reaction is coupled to something you know to be endergonic, like the reduction of NAD+ or a SLP reaction, then that energy came from an exergonic reaction.

   SLP is part of glycolysis and Krebs cycle. This is very closely related to your first question. If there's an exergonic reaction in a pathway, that energy will be released. If you don't do something to harness it, it will be lost as heat, which isn't very efficient. So in some pathways, the energy released from an exergonic reaction can be used to phosphorylate a molecule of ADP to become ATP. That is SLP. So it's the pathway that's exergonic and is coupled to the endergonic substrate level phosphorylation.

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