Chapter 23, Problem 43A

Interpretation Introduction

Interpretation:

The properties of tryptophan should be described on the basis of its structure. The class of large molecules from which tryptophan belongs 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.

Explanation of Solution

The polymeric biomolecules which are formed by the polymerization of amino acids are known as proteins.

The structure of tryptophan is:

Tryptophan is an aromatic amino acid and a large molecule. On the basis of structure, it consists of an alpha-amino group, alpha-carboxylic acid group and an indole moiety is present as a side chain which makes the molecule non-polar.

Properties of tryptophan are:

1. It is insoluble in water due to its non-polar nature but soluble in some organic solvents such as hot alcohol.
2. It has high boiling as well as melting point ( $290.5°\text{C}$).
3. It is solid in nature having yellowish-white in colour.
4. It has flat taste and odourless.
5. The melting point and boiling point of Tryptophan is high as the bonds present in the molecule are hard to break.
6. It is used in the biosynthesis of proteins.

Tryptophan is essential for human which is obtained by the body through diet. Thus, on the basis of its properties, tryptophan is known to be a building block of proteins implies it belongs to class of large molecules (amino acid) which is used in the synthesis of protein.