I am trying to figure out something and am stuck. The delta G of various steps are positive, so I am trying to figure out the energy input that drives the catalysis in such a step. For example, specifically, Phosphoglyceromutase which basically moved the phosphate group one carbon (actually swaps carbons with a Phosphate at a His active site)-- nevertheless, the Gibbs free energy is positive yet no ATP used. In fact there are several steps of the process that do NOT use ATP yet are a positive Gibbs value.
Can someone please clearly elucidate how this happens. I understand how glycolysis and Krebs processes are like rolling a rock up a small hill only to have the rock then fall down a massive mountain-- so I understand how there is energy in the bonds that are released that drive ATP and NADH and FADH2 production, but those I believe have a negative Gibbs.
The "uphill" reactions I am not understanding.
Can you also explain the attached graphs
Thank you for the help.