proteiny

Proteiny, or proteins, are large biomolecules composed mainly of amino acids and critical to almost every biological process. They vary in size from tens to thousands of amino acid residues and fold into unique three-dimensional structures that determine their function. Proteiny can be classified by structure (fibrous vs globular), by function (enzymes, structural, transport, signaling, immune, storage, regulatory), or by origin.

Amino acids linked by peptide bonds form polypeptide chains; the sequence is encoded by genes and translated on ribosomes using the genetic code. The resulting polypeptide folds into secondary structures such as alpha helices and beta sheets, then into a tertiary and sometimes quaternary structure, stabilized by hydrogen bonds, disulfide bridges, hydrophobic interactions, and ionic bonds. Proper folding is essential for activity; misfolding can cause disease. Some proteiny require chaperones or post-translational modifications (phosphorylation, glycosylation, trimming) to become active.

Proteiny perform catalytic roles as enzymes, structural roles as components of tissues, transport of molecules (such as hemoglobin and membrane channels), signaling as receptors and hormones, immune defense as antibodies, and storage as ferritin or casein. They also regulate gene expression and cellular processes.

In nutrition, dietary proteiny supply essential amino acids that the body cannot synthesize. Complete proteiny contain all essential amino acids in adequate amounts; incomplete proteiny lack one or more essential amino acids.

Proteiny are synthesized from genetic information in a process coordinated with RNA and ribosomes, then modified and folded in the endoplasmic reticulum and Golgi apparatus before reaching their sites of action or being secreted. Protein turnover balances synthesis and degradation to maintain cellular function.