Residue

A residue is a single molecular unit within a polymer. Residue is thus another term for monomer. Although the term residue is most often used to refer to a specific amino acid within a polypeptide , it is also used to refer to sugars within a carbohydrate molecule and nucleotides within deoxyribonucleic acid (DNA ) or ribonucleic acid (RNA).

A protein or a polypeptide is composed of amino acids linked together by peptide bonds, with amino acids as the monomeric units of the polypeptide. The order of amino acids in a protein is known as the primary structure of that protein. The specific sequence of amino acids in the protein determines its three-dimensional structure and ultimately its function. The amino acids are numbered sequentially, beginning at the amino terminus of the polypeptide. For example, the 45th amino acid in the sequence would be identified as residue 45. Most often, scientists refer to an individual residue using both the name of the amino acid and its position. Therefore, if residue 45 in a particular polypeptide sequence is serine, that residue would be referred to as serine-45.

see also Peptide Bond; Primary Structure; Proteins.

Robert Noiva

Bibliography

Berg, Jeremy M.; Tymoczko, John L.; and Stryer, Lubert (2002). Biochemistry, 5th edition. New York: W. H. Freeman.

Voet, Donald; Voet, Judith G.; and Pratt, Charlotte W. (2002). Fundamentals of Biochemistry, updated edition. New York: Wiley.

res·i·due / ˈrezəˌd(y)oō/ • n. a small amount of something that remains after the main part has gone or been taken or used. ∎ Law the part of an estate that is left after the payment of charges, debts, and bequests. ∎  a substance that remains after a process such as combustion or evaporation.

residue XIV. — (O)F. résidu — L. residuum, sb. use of n. of residuus remaining, f. residēre remain, RESIDE; see -UOUS.
Hence residual (-AL1) XVI. So residuum XVII. — L.