What process describes the addition of a phosphate group to a molecule?

The addition of a phosphate group to a molecule is specifically known as phosphorylation. This process occurs in various biochemical pathways, most notably in cellular signaling and energy transfer. Phosphorylation can significantly alter the activity of a molecule, such as a protein, often activating or deactivating its function. It plays a crucial role in regulating many cellular processes, including metabolic pathways and signal transduction.

In contrast, condensation refers to the process where two molecules combine to form a larger molecule, typically releasing water. Oxidation involves the loss of electrons, leading to an increase in oxidation state, and is often associated with energy release, while hydrolysis involves the breaking down of a compound by the addition of water, often resulting in the breakdown of larger molecules into smaller units. These processes, while important in biochemistry, do not involve the direct addition of a phosphate group, which is the defining feature of phosphorylation.