protein is a/an

Options

A. oligopeptide
B. tripeptide
C. polypetide
D. peptide

Answer

C

Explanation

Proteins are molecules that contain one or more polypeptide chains. A peptide is an amide formed by intermolecular reaction of amino group of one `A A` and carboxyl group of second `A A`. The reaction between two molecules of (similar of different) amino acids proceeding through the combination of the amino group of one molecule with the carboxyl group of the other and the elimination of water) results in the information of a peptide bond `- CO -NH-` between the the two amino acid residues. The product of the reation is called a dipeptide because it is made up of two amino acids. If a third amino acid combines to a dipeptide, the product is called tripeptide. A tripeptide contains three amino acids linked by two peptide linkage. Similarly when four, five or six amino acids are linked, the respective products are known as tetrapeptide, pentapeptide of hexapeptide, respectively.
If there are three to ten `A A` residues, the product is called an oligopeptide when the number of such amino acids is more than ten, then the products are called polypeptides. The terms peptide and polypeptide are often used interchangeably. A polypeptide with more than hundred amino acid residues, having molecular mass higher than 10,000 U is called a protein.