Enzymes are proteins that catalyze, or affect the rate, of chemical reactions without themselves being altered in the process. Specific enzymes catalyze each cellular reaction.
The main role of enzymes during the respiration reaction is to assist in transferring electrons from one molecule to another. These transfers are called “redox” reactions, where the loss of electrons from one molecule (oxidation) must coincide with the addition of electrons to another substance (reduction).
Glycolysis
This first step of the respiration reaction takes place in the cytoplasm, or fluid, of the cell. Glycolysis consists of nine separate chemical reactions, each catalyzed by a specific enzyme.
The key players in glycolysis are the enzyme dehydrodgenase and a coenzyme (non-protein helper) called NAD+. Dehydrodgenase oxidizes glucose by stripping two electrons from it and transferring them to NAD+. In the process glucose is “split” into two molecules of pyruvate, which continue the reaction.
