Chapter 19, Problem 19.3E

Identify the $\text{R}$ group of the side chain in the following amino acids that results in the side-chain classification indicated in parentheses (see Table $19.1$):

a. tyrosine (neutral, polar)

b. glutamate (acidic, polar)

c. methionine (neutral, nonpolar)

d. histidine (basic, polar)

e. cysteine (neutral, polar)

f. valine (neutral, nonpolar)

Interpretation Introduction

(a)

Interpretation:

The $\text{R}$ group of the side chain in the amino acid, tyrosine is to be identified.

Concept introduction:

Amino acids are organic compounds which combine sequentially to generate a protein. They are known as the building blocks of the human body. The main elements present in amino acids are carbon, nitrogen and oxygen while other elements are found in side chains.

Answer to Problem 19.3E

The $\text{R}$ group of the side chain in the amino acid, tyrosine is shown below.

Explanation of Solution

Amino acids are formed by an amine and a carboxylic acid attached to a carbon atom with a characteristic side chain. The carboxylic acid in amino acids is usually in an ionic form and therefore is known as carboxylate group.

The structure of tyrosine is given below.

Figure 1

Therefore, the $\text{R}$ group of the side chain in the amino acid, tyrosine is shown below.

Figure 2

Conclusion

The $\text{R}$ group of the side chain in the amino acid, tyrosine is shown in Figure 2.

Interpretation Introduction

(b)

Interpretation:

The $\text{R}$ group of the side chain in the amino acid, glutamate is to be identified.

Concept introduction:

Amino acids are organic compounds which combine sequentially to generate a protein. They are known as the building blocks of the human body. The main elements present in amino acids are carbon, nitrogen and oxygen while other elements are found in side chains.

Answer to Problem 19.3E

The $\text{R}$ group of the side chain in the amino acid, glutamate is shown below.

Explanation of Solution

Amino acids are formed by an amine and a carboxylic acid attached to a carbon atom with a characteristic side chain. The carboxylic acid in amino acids is usually in an ionic form and therefore is known as carboxylate group.

The structure of glutamate is given below.

Figure 3

Therefore, the $\text{R}$ group of the side chain in the amino acid, glutamate is shown below.

Figure 4

Conclusion

The $\text{R}$ group of the side chain in the amino acid, glutamate is shown in Figure 4.

Interpretation Introduction

(c)

Interpretation:

The $\text{R}$ group of the side chain in the amino acid, methionine is to be identified.

Concept introduction:

Amino acids are organic compounds which combine sequentially to generate a protein. They are known as the building blocks of the human body. The main elements present in amino acids are carbon, nitrogen and oxygen while other elements are found in side chains.

Answer to Problem 19.3E

The $\text{R}$ group of the side chain in the amino acid, methionine is shown below.

Explanation of Solution

Amino acids are formed by an amine and a carboxylic acid attached to a carbon atom with a characteristic side chain. The carboxylic acid in amino acids is usually in an ionic form and therefore is known as carboxylate group.

The structure of methionine is given below.

Figure 5

Therefore, the $\text{R}$ group of the side chain in the amino acid, methionine is shown below.

Figure 6

Conclusion

The $\text{R}$ group of the side chain in the amino acid, methionine is shown in Figure 6.

Interpretation Introduction

(d)

Interpretation:

The $\text{R}$ group of the side chain in the amino acid, histidine is to be identified.

Concept introduction:

Amino acids are organic compounds which combine sequentially to generate a protein. They are known as the building blocks of the human body. The main elements present in amino acids are carbon, nitrogen and oxygen while other elements are found in side chains.

Answer to Problem 19.3E

The $\text{R}$ group of the side chain in the amino acid, histidine is shown below.

Explanation of Solution

Amino acids are formed by an amine and a carboxylic acid attached to a carbon atom with a characteristic side chain. The carboxylic acid in amino acids is usually in an ionic form and therefore is known as carboxylate group.

The structure of histidine is given below.

Figure 7

Therefore, the $\text{R}$ group of the side chain in the amino acid, histidine is shown below.

Figure 8

Conclusion

The $\text{R}$ group of the side chain in the amino acid, histidine is shown in Figure 8.

Interpretation Introduction

(e)

Interpretation:

The $\text{R}$ group of the side chain in the amino acid, cysteine is to be identified.

Concept introduction:

Amino acids are organic compounds which combine sequentially to generate a protein. They are known as the building blocks of the human body. The main elements present in amino acids are carbon, nitrogen and oxygen while other elements are found in side chains.

Answer to Problem 19.3E

The $\text{R}$ group of the side chain in the amino acid, cysteine is shown below.

Explanation of Solution

Amino acids are formed by an amine and a carboxylic acid attached to a carbon atom with a characteristic side chain. The carboxylic acid in amino acids is usually in an ionic form and therefore is known as carboxylate group.

The structure of cysteine is given below.

Figure 9

Therefore, the $\text{R}$ group of the side chain in the amino acid, cysteine is shown below.

Figure 10

Conclusion

The $\text{R}$ group of the side chain in the amino acid, cysteine is shown in Figure 10.

Interpretation Introduction

(f)

Interpretation:

The $\text{R}$ group of the side chain in the amino acid, valine is to be identified.

Concept introduction:

Amino acids are organic compounds which combine sequentially to generate a protein. They are known as the building blocks of the human body. The main elements present in amino acids are carbon, nitrogen and oxygen while other elements are found in side chains.

Answer to Problem 19.3E

The $\text{R}$ group of the side chain in the amino acid, valine is shown below.

Explanation of Solution

Amino acids are formed by an amine and a carboxylic acid attached to a carbon atom with a characteristic side chain. The carboxylic acid in amino acids is usually in an ionic form and therefore is known as carboxylate group.

The structure of valine is given below.

Figure 11

Therefore, the $\text{R}$ group of the side chain in the amino acid, valine is shown below.

Figure 12

Conclusion

The $\text{R}$ group of the side chain in the amino acid, valine is shown in Figure 12.