Glycan biosynthesis is the process by which complex carbohydrates, known as glycans, are formed in living organisms. These glycans are essential for various biological functions, including cell recognition, signaling, and structural integrity. The biosynthesis involves a series of enzymatic reactions that link simple sugar units, or monosaccharides, into larger, branched structures. The process typically occurs in the endoplasmic reticulum and Golgi apparatus of cells, where specific enzymes, such as glycosyltransferases, catalyze the addition of sugar moieties. Glycan biosynthesis is crucial for the proper functioning of proteins and lipids, influencing their stability and interactions within the cell and with other cells.