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. So following our enzymeatic reaction these coenzymes, known as Co substrates usually change themselves. And to actually regenerate that Co substrate we have to undergo some other type of reaction that usually involves energy. Now, one example of a prosthetic group, basically a Co enzyme that tightly binds to our enzyme is the heme group.