Chapter 9, Problem 9.40EP

(a)

Interpretation Introduction

Interpretation: The validation about the given amino acid being a D-amino acid or an L-amino acid has to be answered.

Concept introduction: If ${\text{NH}}_{\text{2}}$ is placed on the right side of the horizontal line, it is a D-isomer.  If ${\text{NH}}_{\text{2}}$ is placed on the left side of the horizontal line, then it is a L-isomer.

(b)

Interpretation Introduction

Interpretation: The validation about the given amino acid being a polar amino acid or a nonpolar amino acid has to be answered.

Concept introduction: The amino acid that has one amine group, one carboxyl group and nonpolar side chain is called non-polar amino acid.

The amino acid that has one amine group, one carboxyl group and polar side chain is called polar amino acid.

(c)

Interpretation Introduction

Interpretation: The validation about the given amino acid being a standard or a nonstandard amino acid has to be answered.

Concept introduction: The amino acids that are found in proteins are called standard amino acids.  There are 20 standard amino acids.

(d)

Interpretation Introduction

Interpretation: The validation about the given amino acid being an essential amino acid or a non-essential amino acid has to be answered.

Concept introduction: The standard amino acids that are required for the protein synthesis are called essential amino acids.  The human body cannot synthesise these standard amino acids in sufficient amounts and should be included in the diet.