Peptides are short chains of amino acids, which are the building blocks of proteins. In a peptide molecule, amino acids are linked together by peptide bonds. The length of a peptide can vary, ranging from just a few amino acids to several dozen. When a peptide consists of approximately 2 to 50 amino acids, it is typically referred to as an "oligopeptide," while longer chains of amino acids are considered proteins.

Peptides play crucial roles in biological processes and are involved in various physiological functions in the human body, including:

Hormones: Some well-known peptides function as hormones, such as insulin, which regulates blood sugar levels, and glucagon, which has the opposite effect of insulin.

Neuropeptides: These are peptides that act as neurotransmitters or neuromodulators in the nervous system, influencing the transmission of signals between nerve cells. Examples include substance P and endorphins.

Antibiotics: Some peptides have antimicrobial properties and are used in the body's defense against pathogens. For example, cathelicidin is an antimicrobial peptide produced by the immune system.

Enzymes: Many enzymes responsible for facilitating chemical reactions in the body are composed of peptides. These enzymes play essential roles in digestion, metabolism, and other biological processes.

Cell Signaling: Peptides can act as signaling molecules, helping to regulate various cellular processes, including growth, differentiation, and apoptosis (cell death).

Transport: Some peptides assist in transporting substances across cell membranes or within the bloodstream. For example, angiotensin-converting enzyme (ACE) plays a role in regulating blood pressure.

Structural Support: In addition to their functional roles, peptides can contribute to the structural integrity of various tissues and proteins. Collagen, for instance, is a fibrous protein made up of peptide chains and is essential for skin, tendons, and bone strength.

Researchers have also been exploring the potential therapeutic applications of peptides, including the development of peptide-based drugs. These drugs can target specific cellular processes, receptors, or enzymes and are used in areas such as cancer treatment, diabetes management, and immunotherapy.

Peptides are a diverse and biologically significant class of molecules with a wide range of functions in the body. They continue to be a subject of extensive research in various scientific and medical fields due to their potential for understanding and treating various health conditions.