Question

What does phosphorylation do to a molecule?

Answer 1

It changes the conformation and/or function of the molecule.

Explanation:

Phosphorylation is the addition of a phosphate group (`PO""_4^(3-)`) to a molecule, usually a protein. Phosphate has significant mass and charge, therefore it can change the folding (conformation) of the protein it attaches to (see image below).

Changing the conformation of a protein also affects it's function; most significantly in enzymes. When enzymes change conformation, their ability to bind their substrates alters. Phosphorylation can stimulate or inhibit the function of the molecule it attaches to and is therefore an essential control mechanism for the cell.

Such a conformational change is often stimulatory, but can also be inhibitory. Kinases are the enzymes that transfer a phosphate group to a molecule.