Chain: Difference between revisions
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The term ''chain'', in biochemistry, usually denotes either a polypeptide chain or a polynucleotide chain. A polypeptide chain is a sequence of [[amino acids]] covalently linked by [[peptide bonds]]. A short polypeptide consisting of 50 or fewer amino acids is termed a [[peptide]]. A polynucleotide chain is a sequence of [[standard residues|nucleotides]] covalently linked by ribose (or deoxyribose)-phosphate bonds, e.g. either [[DNA]] or [[RNA]]. | The term ''chain'', in biochemistry, usually denotes either a polypeptide chain or a polynucleotide chain. A polypeptide chain is a sequence of [[amino acids]] covalently linked by [[peptide bonds]]. A short polypeptide consisting of 50 or fewer amino acids is termed a [[peptide]]. A polynucleotide chain is a sequence of [[standard residues|nucleotides]] covalently linked by ribose (or deoxyribose)-phosphate bonds, e.g. either [[DNA]] or [[RNA]]. | ||
Polypeptide ([[protein]]) chains are linear, with rare exceptions where a side-chain forms an [[isopeptide bond]] | Polypeptide ([[protein]]) chains are linear, with rare exceptions where a side-chain forms an [[isopeptide bond]]. Polypeptide chains may be covalently linked together, most commonly by [[disulfide bonds]]. | ||
Protein molecules may consist of one or more polypeptide chains, homo-oligomers or hetero-oligomers, homo-multimers or hetero-multimers. The functional form of the molecule, termed the [[biological unit]], often contains a different number of chains than does the crystallographic [[asymmetric unit]]. Examples are given in the article on [[biological units]]. | Protein molecules may consist of one or more polypeptide chains, homo-oligomers or hetero-oligomers, homo-multimers or hetero-multimers. The functional form of the molecule, termed the [[biological unit]], often contains a different number of chains than does the crystallographic [[asymmetric unit]]. Examples are given in the article on [[biological units]]. | ||