Peptides vs Proteins are short chains of amino acids that your body uses to perform vital functions, such as digesting food, controlling hunger, regulating hormones, and controlling cell movement. Your body also makes peptides to help build muscle, lose fat, and improve skin and hair health. Peptides have been used as medicines for about 100 years and have been incorporated into oral supplements, creams, and pills sold for anti-aging, weight loss, and muscle building.

Although both peptides and proteins consist of amino acid chains, they are different in size and structure. Typically, peptides are shorter than proteins, at least 50 amino acids in length. The difference in length helps scientists distinguish peptides from proteins, which are defined as long string-like molecules that display four levels of structural complexity—primary (a sequence of amino acid side chains), secondary (structures such as alpha helices and beta sheets), tertiary, and quaternary (complexes of multiple protein subunits).

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In some cases, a protein’s tertiary structure is stabilized by covalent cross-linkages between adjacent amino acids, known as disulfide bonds. This feature allows proteins to adopt stable conformations that facilitate their biological function.

Most peptides are secreted by endocrine cells and bind to receptors on the surface of other cells to transmit long-distance chemical signals. For example, if blood glucose levels rise after eating, specialized cells in your pancreas release the peptide insulin, which binds to cells in the liver and other tissues to allow them to take up glucose from the blood. This process lowers blood sugar and restores normal glucose levels.