Covalent modifications are chemical changes that occur when a molecule forms a stable bond with another molecule through the sharing of electron pairs. This process often involves the addition or removal of specific functional groups, such as phosphate or methyl groups, to proteins or other biomolecules. These modifications can significantly alter the function, activity, or stability of the modified molecule. One common example of covalent modification is phosphorylation, where a phosphate group is added to a protein, often regulating its activity. Other types include acetylation and ubiquitination, which can influence gene expression and protein degradation, respectively. These modifications play crucial roles in various biological processes, including cell signaling and metabolism.