Enzymes are organic catalysts which aid in facilitating chemical reactions in the body. When functioned properly homeostasis is maintained.
There are a few vital characteristics to mention here. First we have to know about which ions we're talking about as the cellular membrane is semi-permeable (lets some flow freely through the membrane and some not), it depends on the size of the compounds, and also the charge that a molecule has.
ATP is the most important product of the krebs cycle(36 moles)
