A peptide is a short sequence of chained amino acids. Amino acids in a peptide are linked to one another in a sequence called a peptide bond. Proteins are distinguished from peptides by the amount of aminos in a chain. Peptide chains are much shorter than proteins. Two or more amino acids are typically regarded as a peptide bond. Proteins are long molecules made up of peptide chains that contain fifty or more bonds of aminos. Enzymes within the body break down and digest protein into peptides. These peptides are then utilised throughout the body to serve a multitude of functions. For example, some peptides are adapted to deliver hormones around the bodily system.
Cells require proteins and peptides to serve their individual functions. Proteins serve to structure cells, tissue and organs, whereas peptides dictate and regulate the activities of different cell types.
Peptides function as an indispensable signalling molecule. Neuropeptides, peptide hormones and polypeptide growth factors all rely on the transmission of signals between cells. For example: pancreatic β-cells release the peptide hormone insulin that facilitates the storage and absorption of glucose.
Another example would be Oxytocin. This neuropeptide is secreted by the pituitary gland and is produced by hypothalamic neurons. Oxytocin is vital for neurological function as well as protection from cardiovascular disease. "