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 a peptide bond (example needed). Polypeptide chains may be covalently linked together, most commonly by disulfide bonds. | Polypeptide ([[protein]]) chains are linear, with rare exceptions where a side-chain forms a peptide bond (example needed). 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]]. | ||
Revision as of 23:42, 9 September 2013
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 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 a peptide bond (example needed). 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.