Answered

For each side chain given, state whether it would exist in that form at the Isoelectric Point or at Physiological pH.

(a) [tex]\( R = \text{CH}_2\text{- CH}_2\text{- O - C - OH} \)[/tex]
(b) [tex]\( R = \text{- CH}_2\text{- CH}_2\text{- C=O} \)[/tex]
(c) [tex]\( R = \text{- CH}_2\text{- CH}_2\text{- CH}_2\text{- CH}_2\text{- NH}_3^{+} \)[/tex]
(d) [tex]\( R = \text{- CH}_2\text{- CH}_2\text{- CH}_2\text{- CH}_2\text{- NH}_2 \)[/tex]



Answer :

GinnyAnswer
Certainly! Let's analyze each side chain and determine its form at the isoelectric point and at physiological pH:

(a) [tex]\( R = \text{CH}_2 - \text{CH}_2 - \text{O} - \text{C} - \text{OH} \)[/tex]

1. Isoelectric Point:
At the isoelectric point (pI), an amino acid may have both protonated carboxyl groups (–COOH) and protonated amino groups. However, carboxyl groups can also be deprotonated (–COO⁻), depending on the specific amino acid and its pI.
- Form at the isoelectric point:
[tex]\[ \text{CH}_2 - \text{CH}_2 - \text{O} - \text{C} - \text{OH} \, / \, \text{COO}^- \][/tex]

2. Physiological pH (approximately 7):
At physiological pH, which is typically around 7, carboxyl groups are usually deprotonated to form –COO⁻.
- Form at physiological pH:
[tex]\[ \text{CH}_2 - \text{CH}_2 - \text{O} - \text{C} - \text{COO}^- \][/tex]

(b) [tex]\( R =- \text{CH} \, \text{H}_2 - \text{CH}_2 - \text{C}^{\text{in}} - \text{O} \)[/tex]

1. Isoelectric Point:
This structure is somewhat unclear, but assuming it includes a carboxyl group, at the isoelectric point, the form can be either protonated (–COOH) or deprotonated (–COO⁻).
- Form at the isoelectric point:
[tex]\[ \text{CH}_2 - \text{CH}_2 - \text{COOH} \, / \, \text{COO}^- \][/tex]

2. Physiological pH:
At physiological pH, carboxyl groups are typically deprotonated to form –COO⁻.
- Form at physiological pH:
[tex]\[ \text{CH}_2 - \text{CH}_2 - \text{COO}^- \][/tex]

(c) [tex]\( R =- \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{NH}_3^{+} \)[/tex]

1. Isoelectric Point:
At the isoelectric point, amino groups (–NH2) may be protonated to form –NH3⁺ or remain neutral. This depends on the specific pI of the amino acid.
- Form at the isoelectric point:
[tex]\[ \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{NH3}^+ \, / \, \text{NH2} \][/tex]

2. Physiological pH:
At physiological pH (approximately 7), amino groups are usually protonated to form –NH3⁺.
- Form at physiological pH:
[tex]\[ \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{NH3}^+ \][/tex]

(d) [tex]\( R =- \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{NH}_2 \)[/tex]

1. Isoelectric Point:
At the isoelectric point, amino groups can be protonated to form –NH3⁺ or remain neutral (–NH2), depending on the specific pI.
- Form at the isoelectric point:
[tex]\[ \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{NH3}^+ \, / \, \text{NH2} \][/tex]

2. Physiological pH:
At physiological pH, amino groups are typically protonated to form –NH3⁺.
- Form at physiological pH:
[tex]\[ \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{NH3}^+ \][/tex]

In summary:
1. (a)
- At the isoelectric point: [tex]\( \text{CH}_2 - \text{CH}_2 - \text{O} - \text{C} - \text{OH} \, / \, \text{COO}^- \)[/tex]
- At physiological pH: [tex]\( \text{CH}_2 - \text{CH}_2 - \text{O} - \text{C} - \text{COO}^- \)[/tex]

2. (b)
- At the isoelectric point: [tex]\( \text{CH}_2 - \text{CH}_2 - \text{COOH} \, / \, \text{COO}^- \)[/tex]
- At physiological pH: [tex]\( \text{CH}_2 - \text{CH}_2 - \text{COO}^- \)[/tex]

3. (c)
- At the isoelectric point: [tex]\( \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{NH3}^+ \, / \, \text{NH2} \)[/tex]
- At physiological pH: [tex]\( \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{NH3}^+ \)[/tex]

4. (d)
- At the isoelectric point: [tex]\( \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{NH3}^+ \, / \, \text{NH2} \)[/tex]
- At physiological pH: [tex]\( \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{CH}_2 - \text{NH3}^+ \)[/tex]

Other Questions