Chapter 21, Problem 7A

Interpretation Introduction

Interpretation: Hydrophilic and hydrophobic side chains needs to be explained.

Concept Introduction:

Substances that have a special affinity for water are called hydrophilic in nature.

The ones that naturally repel water and cause droplets to form are called hydrophobic.

Explanation of Solution

Hydrophilic as the name implies Hydro-water and philic - dear. Polarity comes from the difference of 0.5-1.9 in electronegativity between bonded molecules. These groups distort the polypeptide chain from each other and interact with water. Hydrophobic groups distort away from the chains on this side. Amino acids are grouped according to how the chains are on their side. The polar amino acids have side chains, which are hydrophilic, i.e. they seek contact with aqueous solutions. The opposite of non-polar amino acids (hydrophobic), they avoid contact with fluid. These compounds play a major role in protein binding and provide protein in its 3-D structure.