Energy and Metabolism

ID #1085

Are the first three steps of glycolysis endergonic or exergonic? I think the first and third steps are endergonic...but isn't the second one is just an isomerization?

Yes, that's correct. The first three steps collectively are called the Investment Phase, since overall they require an input of energy from the cell's available store of ATP. The only point of clarification I'd like to make is that everyone should remember what our frame of reference is when using terms like "endergonic" and "exergonic." Unless you are told otherwise, if it is said that Step 1 in glycolysis is endergonic, this is from the perspective of the metabolic pathway, not the coupled reaction.

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