What is meant by prosthetic group on a protein?

A prosthetic group is a non-polypeptide unit that is tightly and permanently attached to a protein and is essential for the protein's biological activity. These groups can be organic molecules, such as heme in hemoglobin, or metal ions, like zinc in certain enzymes. They play crucial roles in the protein's function, such as facilitating electron transfer or stabilizing the protein's structure. Overall, prosthetic groups are integral for the proper functioning of many proteins.