But we can categorize Cofactors into two groups, into two categories. We have metal ions and we also have organic molecules known as coenzymes that are usually formed from vitamins. Now, one example of a metal ion that acts as a cofactor for carbonic and hydrates is the zinc atom. And we'll talk about that in detail in a future electra. Now, coenzymes can bind onto proteins either strongly or weakly. And if we have a coenzyme that is bound very tightly to the enzyme that is known as a prosthetic group number four enzymes are extremely efficient and extremely specific molecules.