Chapter 25.2, Problem 4PTS

(a)

Interpretation Introduction

Interpretation:

The form of amino acid which seems to predominate at the given pH for the set of amino acids need to be drawn.

Concept introduction:

Amino acid has both carboxylic acid and amine functional group.  In presence of acid or base either one form will predominate which depends upon the pK_a value.  Usually the carboxylic acid group is deprotonated first and then the amino group is deprotonated.  At higher pH the carboxylic acid gets deprotonated and at lower pH the amino group gets protonated.

• The carboxylic acid form will predominate over carboxylate form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• The protonated form of $\alpha$ amino will predominate over the  $\alpha$ amino form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• If side chain is present the same rule as above applies.

To draw: the form of alanine which predominates at pH of 10

(b)

Interpretation Introduction

Interpretation:

The form of amino acid which seems to predominate at the given pH for the set of amino acids need to be drawn.

Concept introduction:

Amino acid has both carboxylic acid and amine functional group.  In presence of acid or base either one form will predominate which depends upon the pK_a value.  Usually the carboxylic acid group is deprotonated first and then the amino group is deprotonated.  At higher pH the carboxylic acid gets deprotonated and at lower pH the amino group gets protonated.

• The carboxylic acid form will predominate over carboxylate form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• The protonated form of $\alpha$ amino will predominate over the  $\alpha$ amino form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• If side chain is present the same rule as above applies.

To draw: the form of proline which predominates at pH of 10

(c)

Interpretation Introduction

Interpretation:

The form of amino acid which seems to predominate at the given pH for the set of amino acids need to be drawn.

Concept introduction:

Amino acid has both carboxylic acid and amine functional group.  In presence of acid or base either one form will predominate which depends upon the pK_a value.  Usually the carboxylic acid group is deprotonated first and then the amino group is deprotonated.  At higher pH the carboxylic acid gets deprotonated and at lower pH the amino group gets protonated.

• The carboxylic acid form will predominate over carboxylate form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• The protonated form of $\alpha$ amino will predominate over the  $\alpha$ amino form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• If side chain is present the same rule as above applies.

To draw: the form of tyrosine which predominates at pH of 9

(d)

Interpretation Introduction

Interpretation:

The form of amino acid which seems to predominate at the given pH for the set of amino acids need to be drawn.

Concept introduction:

Amino acid has both carboxylic acid and amine functional group.  In presence of acid or base either one form will predominate which depends upon the pK_a value.  Usually the carboxylic acid group is deprotonated first and then the amino group is deprotonated.  At higher pH the carboxylic acid gets deprotonated and at lower pH the amino group gets protonated.

• The carboxylic acid form will predominate over carboxylate form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• The protonated form of $\alpha$ amino will predominate over the  $\alpha$ amino form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• If side chain is present the same rule as above applies.

To draw: the form of asparagine which predominates at physiological pH

(e)

Interpretation Introduction

Interpretation:

The form of amino acid which seems to predominate at the given pH for the set of amino acids need to be drawn.

Concept introduction:

Amino acid has both carboxylic acid and amine functional group.  In presence of acid or base either one form will predominate which depends upon the pK_a value.  Usually the carboxylic acid group is deprotonated first and then the amino group is deprotonated.  At higher pH the carboxylic acid gets deprotonated and at lower pH the amino group gets protonated.

• The carboxylic acid form will predominate over carboxylate form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• The protonated form of $\alpha$ amino will predominate over the  $\alpha$ amino form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• If side chain is present the same rule as above applies.

To draw: the form of histidine which predominates at physiological pH

(f)

Interpretation Introduction

Interpretation:

The form of amino acid which seems to predominate at the given pH for the set of amino acids need to be drawn.

Concept introduction:

Amino acid has both carboxylic acid and amine functional group.  In presence of acid or base either one form will predominate which depends upon the pK_a value.  Usually the carboxylic acid group is deprotonated first and then the amino group is deprotonated.  At higher pH the carboxylic acid gets deprotonated and at lower pH the amino group gets protonated.

• The carboxylic acid form will predominate over carboxylate form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• The protonated form of $\alpha$ amino will predominate over the  $\alpha$ amino form if ${\text{pH<pK}}_{\text{a}}$ and vice-versa.
• If side chain is present the same rule as above applies.

To draw : the form of glutamic acid which predominates at pH of 3