Enzymes catalyse biochemical reactions Co-enzymes and Cofactors Electron transport The Working Cell. Potential Energy, the stored water has the potential to do work. Kinetic Energy, the water moving down the spillway is doing work. Chemical reactions can use up, or produce useful energy. Endergonic reactions require an energy input.
Exergonic reactions produce an energy output.
These reactions are exergonic. Similarly, we must add energy to shift from a stable form to an unstable form. We say the protein is phosphorylated. Cells need to dole out energy in tiny subunits. Enzymes are unchanged by catalyzing a reaction, so they can be re-used.