Peptides are natural or synthetic compound comprising of two or more amino acids linked through an amide formation.
This covalent chemical bond formed between a carboxyl group of one amino acid to a nitrogen atom of another amino acid.
Peptides are differentiate from protein base on the number of amino acid residues. The shortest peptides are called dipeptides which consisting of 2 amino acids joint together by a single peptide bond.
Polypeptide consist of 10-50 amino acids residues are called peptides, peptides contain more than 50 amino acids often refer as protein. Peptides often classified by function or by synthesis.
Peptides classified by function including but not limited to hormones, neuropeptides, HLA peptides, infectious disease, cancer peptides.
Proteins and peptides are fundamental components of cells that carry out important biological functions.
Proteins give cells their shape, for example, and they respond to signals transmitted from the extracellular environment. Certain types of peptides play key roles in regulating the activities of other molecules.
Structurally, proteins and peptides are very similar, being made up of chains of amino acids that are held together by peptide bonds (also called amide bonds). So, what distinguishes a peptide from a protein?
The basic distinguishing factors are size and structure. Peptides are smaller than proteins. Traditionally, peptides are defined as molecules that consist of between 2 and 50 amino acids, whereas proteins are made up of 50 or more amino acids.
In addition, peptides tend to be less well defined in structure than proteins, which can adopt complex conformations known as secondary, tertiary, and quaternary structures.
Functional distinctions may also be made between peptides and proteins.
Peptides, however, may be subdivided into oligopeptides, which have few amino acids (e.g., 2 to 20), and polypeptides, which have many amino acids.
Proteins are formed from one or more polypeptides joined together. Hence, proteins essentially are very large peptides. In fact, some researchers use the term peptide to refer specifically to oligopeptides, or otherwise relatively short amino acid chains, with the term polypeptide being used to describe proteins, or chains of 50 or more amino acids.