EBK ESSENTIAL ORGANIC CHEMISTRY
EBK ESSENTIAL ORGANIC CHEMISTRY
3rd Edition
ISBN: 8220100659461
Author: Bruice
Publisher: PEARSON
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Chapter 17, Problem 29P

Draw the predominant form of the following amino acids at physiological pH (7.4):

  1. a. Lysine
  2. b. Arginine
  3. c. tyrosine

(a)

Expert Solution
Check Mark
Interpretation Introduction

Interpretation:

The predominant form of lysine at physiological pH (7.4) has to be drawn.

Concept introduction:

Acid-base properties of Amino acids:

Every amino acid has a carbonyl group and an amino group, and each group can exist in an acidic form or a basic form, depending on pH of the solution in which the amino acid is dissolved.

The compound exists primarily in the acidic form in solutions that are more acidic than their pKa values, and primarily in the basic form (without their protons) in solutions that are more basic than their pKa values.

At pH=7, pH of the solution is greater than the pKa of the carboxyl group then carboxyl group is in the basic form, but less than the pKa of the protonated amino group then amino acid is in the acidic form.

Answer to Problem 29P

The predominant form of lysine at physiological pH (7.4)

  EBK ESSENTIAL ORGANIC CHEMISTRY, Chapter 17, Problem 29P , additional homework tip  1

Explanation of Solution

The predominant form of glutamine at physiological pH (7.4)

  EBK ESSENTIAL ORGANIC CHEMISTRY, Chapter 17, Problem 29P , additional homework tip  2

pKa, α-COOH = 2.17 Value is lesser than the given pH = 7.4; carbonyl group has to be in the basic form so carbonyl group is deprotonated and exist in negative charges (carboxylate ion); pKa, α-NH3 = 9.04 value is greater than the given pH = 7.4 so amino group must in the acidic form so the amino group gets protonated. The two amine groups do not protonated as the lone pairs involves in the delocalization.

(b)

Expert Solution
Check Mark
Interpretation Introduction

Interpretation:

The predominant form of arginine at physiological pH (7.4) has to be drawn.

Concept introduction:

Acid-base properties of Amino acids:

Every amino acid has a carbonyl group and an amino group, and each group can exist in an acidic form or a basic form, depending on pH of the solution in which the amino acid is dissolved.

The compound exists primarily in the acidic form in solutions that are more acidic than their pKa values, and primarily in the basic form (without their protons) in solutions that are more basic than their pKa values.

At pH=7, pH of the solution is greater than the pKa of the carboxyl group then carboxyl group is in the basic form, but less than the pKa of the protonated amino group then amino acid is in the acidic form.

Answer to Problem 29P

The predominant form of lysine at physiological pH (7.4)

  EBK ESSENTIAL ORGANIC CHEMISTRY, Chapter 17, Problem 29P , additional homework tip  3

Explanation of Solution

The predominant form of lysine at physiological pH (7.4)

  EBK ESSENTIAL ORGANIC CHEMISTRY, Chapter 17, Problem 29P , additional homework tip  4

pKa, α-COOH = 2.17 Value is lesser than the given pH = 7.4; carbonyl group has to be in the basic form so carbonyl group is deprotonated and exist in negative charges (carboxylate ion); pKa, α-NH3 = 9.04 value is greater than the given pH = 7.4 so amino group must in the acidic form so the amino group gets protonated. The two amine groups do not protonated as the lone pairs involves in the delocalization.

(c)

Expert Solution
Check Mark
Interpretation Introduction

Interpretation:

The predominant form of tyrosine at physiological pH (7.4) has to be drawn.

Concept introduction:

Acid-base properties of Amino acids:

Every amino acid has a carbonyl group and an amino group, and each group can exist in an acidic form or a basic form, depending on pH of the solution in which the amino acid is dissolved.

The compound exists primarily in the acidic form in solutions that are more acidic than their pKa values, and primarily in the basic form (without their protons) in solutions that are more basic than their pKa values.

At pH=7, pH of the solution is greater than the pKa of the carboxyl group then carboxyl group is in the basic form, but less than the pKa of the protonated amino group then amino acid is in the acidic form.

Answer to Problem 29P

The predominant form of tyrosine at physiological pH (7.4)

  EBK ESSENTIAL ORGANIC CHEMISTRY, Chapter 17, Problem 29P , additional homework tip  5

Explanation of Solution

The predominant form of tyrosine at physiological pH (7.4)

  EBK ESSENTIAL ORGANIC CHEMISTRY, Chapter 17, Problem 29P , additional homework tip  6

pKa, α-COOH = 2.20 Value is lesser than the given pH = 7.4; carbonyl group has to be in the basic form so carbonyl group is deprotonated and exist in negative charges (carboxylate ion); pKa, α-NH3 = 9.11 value is greater than the given pH = 7.4 so amino group must in the acidic form so the amino group gets protonated.

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Chapter 17 Solutions

EBK ESSENTIAL ORGANIC CHEMISTRY

Ch. 17.5 - Prob. 12PCh. 17.6 - Prob. 13PCh. 17.6 - What amino acid would be formed using the...Ch. 17.6 - What amino acid would be formed when the aldehyde...Ch. 17.7 - Pig liver esterase is an enzyme that catalyzes the...Ch. 17.8 - Prob. 17PCh. 17.8 - Prob. 18PCh. 17.8 - Prob. 19PCh. 17.8 - Prob. 20PCh. 17.10 - Prob. 21PCh. 17.10 - Prob. 22PCh. 17.10 - Why does cyanogen bromide not cleave on the C-side...Ch. 17.10 - Prob. 24PCh. 17.10 - Prob. 26PCh. 17.12 - Prob. 27PCh. 17.13 - a. Which would have the greatest percentage of...Ch. 17 - Draw the predominant form of the following amino...Ch. 17 - What is the pI of serine?Ch. 17 - Prob. 31PCh. 17 - Prob. 32PCh. 17 - Which would have a higher percentage of negative...Ch. 17 - Draw the form of aspartate that predominates at...Ch. 17 - Prob. 35PCh. 17 - A professor was preparing a manuscript for...Ch. 17 - a. Why is the pKa of the glutamate side chain...Ch. 17 - Prob. 38PCh. 17 - Determine the amino acid sequence of a polypeptide...Ch. 17 - Prob. 40PCh. 17 - Prob. 41PCh. 17 - Three peptides were obtained from a trypsin...Ch. 17 - Prob. 43PCh. 17 - After the polypeptide shown here was treated with...Ch. 17 - The disulfide bridges of a polypeptide were...Ch. 17 - -Amino acids can be prepared by treating an...Ch. 17 - Reaction of a polypeptide with carboxypeptidase A...Ch. 17 - Prob. 48PCh. 17 - Prob. 49PCh. 17 - Show how valine can be prepared by a. a Strecker...Ch. 17 - Prob. 51PCh. 17 - Why is proline never found in an -helix?Ch. 17 - Determine the amino acid sequence of a polypeptide...Ch. 17 - Prob. 55PCh. 17 - A chemist wanted to test his hypothesis that the...Ch. 17 - A normal polypeptide and a mutant of the...
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