As discussed earlier? So we have the prosthetic group which basically bind tightly to the enzyme. So these coenzymes bind tightly, usually via Covalent bonds to our enzyme and remain tightly bound during the reaction. And during the reaction they are not actually changed. And so following the reaction those coenzymes are regenerated and they remain unchanged. However, Co substrates bind to our enzyme via weak bonds and usually the Co substrates end up transferring one of the groups on that Co substrate on that coenzyme to our substrate.