(i) Proteins are formed by joining the carboxyl group of one amino to the α – amino group of another acid.
(ii) The bond formed between two amino acids by the elimination of water molecules is called peptide linkage.
(iii) The product formed by linking amino acid molecules through peptide linkage -CO – NH – is called a peptite.
(iv) When two amino acids combined in this way the resulting product is called a dipeptide
(v) Peptide are further designated as tri, tetra or penta peptides accordingly as they contain three, four or five amino acid molecules, same or different.
(vi) In a peptide the amino acid that contains the free amino group is called the N – terminal residue (written on L.H.S).
(vii) The amino acid that contains the free carboxyl group is called the C – terminal residue (written on R.H.S).
(viii) If a large number of α – amino acids (100 to 1000) are joined by peptide bonds the resulting polyamide is called polypeptide.
(ix) By convention a peptide having molecular weight upto 10,000 is called polypeptide.
(x) While a peptide having a molecular mass more than 10,000 is called a protein.
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