After discovering the synthesis reaction for chaining two amino acids together in 1901, chemist Emil Fischer exhibited his finding at a conference and coined the term “peptide”.^[1] The word “peptide” comes from the Greek word “peptos,” which means “cooked, digested”.^[2]

Linked amino acids make up a peptide. When only two or three amino acids are bonded together, they are called dipeptides or tripeptides. Peptides which grow long through linking multiple amino acids together are called proteins. However, there’s not a clear dividing line between what’s a peptide and what’s a protein; protein classification is not a standardized process because scientists have not agreed on a molecular weight or amino acid length cutoff for the two terms.

Peptides are important because they serve as hormones, neuromodulators, antioxidants, immune responders, and many other purposes to carry out the needs of our bodies. Some examples of important peptides and their main function(s) include:

• Vasopressin — blood pressure hormone and memory neuromodulator
• Oxytocin — social hormone and neuromodulator
• Neuropeptide Y — appetite neuromodulator
• Endorphins — pain neuromodulator
• Cholecystokinin — satiety hormone
• Peptide YY — satiety hormone
• Calcitonin — calcium homeostasis hormone
• Insulin and Glucagon — blood sugar homeostasis hormones
• Glutathione — antioxidant and transporter
• Carnosine — antioxidant and transporter