Peptide

A molecule made of amino acids joined by peptide bonds. Peptides are generally shorter than proteins, though no universal length boundary separates them.

Amino acid: An organic molecule containing amino and carboxyl groups; amino acids are the subunits of proteins and peptides. Peptides are chains of amino acid residues linked in a specific order.
Ribosomal translation: The cellular process in which ribosomes use messenger RNA to assemble amino acids into a polypeptide. Ribosomes make many peptides and proteins by forming peptide bonds in sequence.
Peptide hormone: A signaling molecule made of amino acid residues that regulates processes such as growth, metabolism, or reproduction. Insulin and glucagon show how peptides can act as systemic signals.
Protein: A biological macromolecule consisting of one or more folded chains of amino acid residues. Proteins are generally longer and structurally more elaborate, but the boundary with peptides is not universal.
Peptide bond: A covalent amide bond linking the carboxyl group of one amino acid to the amino group of another. This bond joins the residues that form a peptide chain.
Solid-phase peptide synthesis: A laboratory method that builds a peptide stepwise while its growing chain remains attached to an insoluble support. It provides controlled chemical assembly of defined peptide sequences.
Insulin: A peptide hormone produced by pancreatic beta cells that helps regulate blood glucose. It is a prominent therapeutic peptide and a classic example of peptide hormone activity.
Polypeptide: A continuous chain of many amino acid residues linked by peptide bonds. The term emphasizes chain length and structure without necessarily implying a functional, folded protein.
Amino acid sequence: The ordered series of amino acid residues in a peptide or protein. The sequence determines a peptide’s chemical identity and influences its shape and activity.
Peptide conformation: The three-dimensional arrangement of atoms in a peptide chain, shaped by bond geometry and molecular interactions. A peptide’s conformation can determine which molecules it binds and how it functions.

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