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What are the N terminus and C terminus of a protein chain?
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Protein
The molecular structure of a peptide (a small protein) consists of a sequence of amino acids.
In biochemistry, a protein is a polypeptide chain consisting of amino acids linked by peptide bonds. Because these chains have a specific directionality, they are defined by their two distinct ends:12
- N terminus: This is the end of the protein chain that features a free -amino group (—NH). By convention, it is written on the left side of the peptide structure.2
- C terminus: This is the end of the protein chain that features a free carboxyl group (—COOH). By convention, it is written on the right side of the peptide structure.2
These termini represent the points where the chain begins and ends, respectively, reflecting the linear sequence of amino acid residues that determines the unique structure and function of each protein.12