Chapter 23, Problem 46A

Interpretation Introduction

Interpretation:

The following statement does make any sense in terms of the nature of the cellular environment should be explained.

The proteins (mostly) having a globular shape are oriented so that they have mostly nonpolar amino acids located inside and polar amino acids on the outer surface.

Concept introduction:

Proteins are polymeric biomolecules which are formed by the polymerisation of amino acids. Amino acids are the organic molecules with $–{\text{NH}}_{\text{2}}$ and −COOH functional groups bonded on same carbon atom of the molecule.

They polymerize by peptide linkage to form dipeptide, oligopeptide and polypeptide molecules. Each peptide bond formation is a condensation reaction that occurs with the elimination of water molecule.

Explanation of Solution

Polar amino acid is directed towards the outside of the protein because of the hydrophilic properties of side chain whereas the nonpolar amino acid is directed towards the inside of protein (R group repelled by water) because of the hydrophobic nature.

The building blocks of all living things are known as cells. The environment of cell is aqueous in nature implies it composed of mostly water. Due to aqueous environment of cell, the polar amino acids are located outside of the molecule whereas nonpolar amino acids are located inside the molecule (few polar amino acids are also present inside). The membrane known as semi-permeable membrane present in the cell allows regulating the quantity of water outside and inside of the cell. Therefore, the given statement makes sense in terms of cellular environment.