Chapter 23, Problem 35A

Interpretation Introduction

Interpretation:

The structures should be drawn for four possible peptides for a four-member chain which can be made by linking together in different orders.

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.

Explanation of Solution

Peptide bonds are identified by the bonding present between carboxyl group of one amino acid and one amino group of other amino acid. Each peptide bond formation is a condensation reaction that occurs with the elimination of water molecule.

The general chemical reaction is:

Where, R and R^’ are side groups.

Four amino acids reacts together to form three peptide bonds.

Possible arrangements of four amino acids are: