Chapter 23, Problem 50A

Interpretation Introduction

Interpretation:

The number of amino acids and peptide bonds present in the following peptide should be determined.

Concept introduction:

Proteins are polymeric biomolecules which are formed by the polymerisation of amino acids. Amino acids are the organic molecules with $–{\text{NH}}_{\text{2}}$ and −COOH functional groups bonded on same carbon atom of the molecule.

They polymerise by peptide linkage to form dipeptide, oligopeptide and polypeptide molecules. Each peptide bond formation is a condensation reaction that occurs with the elimination of water molecule.

Answer to Problem 50A

Four amino acids and three peptide bonds (amide groups −CONH₂) are present.

Explanation of Solution

A chemical bond which is formed between two molecules of amino acid, when carboxyl group of one amino acid reacts with amino group of another amino acid and water is released is known as amide bond.

The given structure is:

In above structure, four different amino acids are present due to the presence of three peptide bonds. Peptide bonds are identified by the bonding present between carboxyl group of one amino acid and amino group of another amino acid. Three amide groups are present in the given structure and the amino acids present on end of the chain (both side) is not bonded to any group.

The structure is shown as:

Thus, in the given structure: Four amino acids and three peptide bonds (amide groups −CONH₂) are present.