BuyFindarrow_forward

Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074

Solutions

Chapter
Section
BuyFindarrow_forward

Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074
Textbook Problem

(a) Draw the Lewis structure for the amino acid valine, showing the amino group and the carboxylic acid group in their un-ionized forms.

(b) Draw the Lewis structure for the zwitterionic form of valine.

(c) Which of these structures will be the predominant form at physiological pH?

(a)

Interpretation Introduction

Interpretation:

The Lewis structure of amino acid valine showing the amino and carboxylic group in their un-ionized form has to be drawn.

Concept introduction: Amino acids are organic compounds that consist of amine group (NH2) as well as a carboxylic acid group (COOH) present at two different ends along with a side chain (R). The side chain is different for different amino acids.

Examples of amino acids include glycine, valine, alanine, and arginine.

The general formula for any amino acid is H2NCH(R)COOH.

Explanation

Valine amino acid is an essential α amino acid and has an isopropyl side group. The side chain is nonploar so valine is non-polar aliphatic amino acid. Side chain (R) for valine is (CH(CH3)2). The neutral structure of valine is its unionized form.

Therefore the structure of un-ionized form  of valine is,

images

(b)

Interpretation Introduction

Interpretation:

The Lewis structure for the zwitterionic form of valine has to be drawn.

Concept introduction: Amino acids are organic compounds that consist of amine group (NH2) as well as a carboxylic acid group (COOH) present at two different ends along with a side chain (R). The side chain is different for different amino acids.

Examples of amino acids include glycine, valine, alanine, and arginine.

The general formula for any amino acid is H2NCH(R)COOH.

Explanation

Zwitter ion is defined as the ion or molecule which contains both positively and negatively charged groups on nonadjacent position. The amino group takes up a proton and becomes protonated and carboxylic acid loses its proton and becomes ionized the resulting structure consisting of (NH3+) and (COO) is called the zwitterionic structure of valine.

Therefore the Zwitterionic structure of valine is,

images

The Zwitterionic structure of valine consists of a positively charged amino group and a negatively charged carboxyl group.

 (c)

Interpretation Introduction

Interpretation:

The predominant form at physiological pH has to be predicted.

Concept introduction: Amino acids are organic compounds that consist of amine group (NH2) as well as a carboxylic acid group (COOH) present at two different ends along with a side chain (R). The side chain is different for different amino acids.

Examples of amino acids include glycine, valine, alanine, and arginine.

The general formula for any amino acid is H2NCH(R)COOH.

Explanation

At low pH values (acidic medium) the amino group takes up the proton and gets protonated (NH2NH3+) and at high pH values (basic medium) the carboxylic group loses its ionizable proton (COOHCOO). But at physiological pH which is nearly equal to 7.4 the amino group present in pronated form and carboxyl group loses its proton resulting in a zwitterionic structure.

At physiological pH the predominant form of valine is the zwitterionic form.

The Solution to Your Study Problems

Bartleby provides explanations to thousands of textbook problems written by our experts, many with advanced degrees!

Get Started

Additional Science Solutions

Find more solutions based on key concepts

Show solutions add

Which two minerals are the major constituents of bone? a. calcium and zinc b. sodium and magnesium c. phosphoru...

Nutrition: Concepts and Controversies - Standalone book (MindTap Course List)

How do eating disorders affect health?

Understanding Nutrition (MindTap Course List)

Find all the answers to your study problems with bartleby.
Textbook solutions plus Q&A. Get As ASAP arrow_forward