Q. 16.7 - An Introduction to General, Organic, and Biological Chemistry

Question

Classify each of the amino acids in problem $16.5$as polar or nonpolar. If polar, indicate if the R group is neutral, acidic, or basic. Indicate if each is hydrophobic or hydrophilic.

Step-by-Step Solution

Answer

The following are the ionized forms of the amino acids glycine, tyrosine (T), glutamic acid, and phenyl alanine:

Step 1: Given data

Amino acids are the building blocks of proteins. These have one hydrogen atom and one amine group.$\left(-{\mathrm{NH}}_2\right)$, one carboxylic acid group $(-\mathrm{COOH})$ and one side chain (R group) attached to the central carbon atom. Proteins are made up of two amino acids linked together by peptide bonds. Depending on the structure, the R group can be polar, neutral, or charged.

Step 2: Introduction

The amino group$\left(-{\mathrm{NH}}_2\right)$ tends to accept a proton $\left({\mathrm{H}}^{+}\right)$in neutral solution, so it is basic in nature. The carboxylic group$(-\mathrm{COOH})$ tends to lose a proton in neutral solution, so it is acidic in nature. The polar amino acids are hydrophilic because they can form hydrogen bonds with water. The nonpolar amino acids are hydrophobic because they do not form hydrogen bonds.

Step 3: Given data

Decide whether each amino acid in glycine is polar or nonpolar. If the R group is polar, specify whether it is neutral, acidic, or basic. Identification of whether they are hydrophobic or hydrophilic

Step 4: Explanation (part a)

Step 5: Given data

Decide whether each amino acid is tyrosine (T), polar or nonpolar. If the R group is polar, specify whether it is neutral, acidic, or basic.Determine whether they are hydrophobic or hydrophilic.

Step 6: Explanation (part b)

Step 7: Given data

Decide whether each amino acid is glutamic acid polar or nonpolar. If the R group is polar, specify whether it is neutral, acidic, or basic. Determine whether they are hydrophobic or hydrophilic.

Step 8: Explanation (part c)

Step 9: Given data

Decide whether each amino acid is phenyl alanine polar or nonpolar. If the R group is polar, specify whether it is neutral, acidic, or basic. Determine whether they are hydrophobic or hydrophilic.

Step 10: Explanation (part d).