A tripeptide is composed of three chained amino acids. Amino acids differ in composition, but each features a carboxyl group and an amino group attached to a central atom, along with a distinguishing functional group. There are 20 different amino acids that can be found in a given tripeptide.
The human body can synthesize around 8,000 different tripeptides. An example is glutathione, which is made in the liver and composed of the amino acids glycine, glutamic acid and cysteine. Glutathione provides immunity and detoxification benefits, and a deficiency of this tripeptide can result in an increase in physical signs of aging, such as wrinkles and poor skin tone, according to SkinStore.com. Another example of a tripeptide is biotinyl tripeptide, which is an ingredient in some mascaras due to its ability to help eyelashes retain their natural thickness and length.
Six of the 20 amino acids that can make up tripeptides feature a hydrocarbon R-group, also called a side chain, attached to the central carbon atom. The simplest example is glycine, which has a hydrogen atom in the location of the molecule where other amino acids feature an R-group. Meanwhile, alanine features a methyl group, which has the chemical structure CH3, as its R-group. Another example is valine, an amino acid with a three-carbon R-group.