prótein

Prótein is a biological macromolecule composed of one or more polypeptide chains folded into a specific three-dimensional shape. In all living organisms proteins perform a vast array of vital roles and are built from long sequences of amino acids linked by peptide bonds. The properties of a protein arise from its sequence and three-dimensional structure.

Proteins have a hierarchy of structure: the primary structure is the amino acid sequence. Higher levels include secondary structures such as alpha helices and beta sheets, followed by tertiary and sometimes quaternary arrangement. The shape determines function, including catalytic activity, binding, transport, or structural support.

There are twenty standard amino acids that form proteins. Nine are essential in adult humans and must be obtained from diet; others can be synthesized. Proteins can be classified by function or by composition as enzymes, structural proteins, transport proteins, hormones, antibodies, or signaling molecules.

Dietary proteins supply amino acids for maintenance and growth. Animal sources such as meat, dairy, and eggs provide complete proteins; many plant sources are incomplete but can supply all essential amino acids when eaten in a varied diet.

In biology and industry, proteins function as enzymes, antibodies, hormones, and therapeutic agents; they are used in biotechnology, food processing, and materials science. Misfolding and aggregation of proteins underlie several diseases.