an amino acid obtainable by hydrolysis of most common proteins, sometimes constituting 5 to 10 percent by weight of the total product. First isolated in 1865 from sericin, a silk protein, serine is one of several so-called nonessential amino acids for mammals; i.e., they can synthesize it from glucose and do not require dietary sources.

Serine and some of its derivatives (e.g., ethanolamine) are also important components of a class of lipids (phospholipids (phospholipid)) found in biological membranes.