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.

Verified step by step guidance

1. Step 1: Recall the structure of amino acids. Each amino acid has a central carbon atom (α-carbon) bonded to an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and a unique R group (side chain). The properties of the R group determine whether the amino acid is polar or nonpolar, and if polar, whether it is neutral, acidic, or basic.
2. Step 2: Classify the amino acid as polar or nonpolar based on the nature of its R group. Nonpolar amino acids have R groups that are primarily hydrocarbons (e.g., alkyl or aromatic groups), while polar amino acids have R groups containing electronegative atoms like oxygen, nitrogen, or sulfur.
3. Step 3: For polar amino acids, determine if the R group is neutral, acidic, or basic. Neutral polar amino acids have R groups with polar functional groups (e.g., hydroxyl, amide) but no charge at physiological pH. Acidic amino acids have R groups with carboxylic acid groups that can donate protons, while basic amino acids have R groups with amine groups that can accept protons.
4. Step 4: Assess whether the amino acid is hydrophobic or hydrophilic. Nonpolar amino acids are generally hydrophobic because their R groups do not interact well with water. Polar amino acids are hydrophilic because their R groups can form hydrogen bonds or ionic interactions with water.
5. Step 5: Apply these classifications to each amino acid in problem 16.5. For each amino acid, identify the R group, classify it as polar or nonpolar, determine if it is neutral, acidic, or basic (if polar), and indicate whether it is hydrophobic or hydrophilic.

Key Concepts

Amino Acid Classification

Amino acids can be classified based on the properties of their side chains (R groups). They are categorized as polar or nonpolar, which affects their interactions with water. Polar amino acids tend to be hydrophilic, while nonpolar amino acids are generally hydrophobic. Understanding this classification is essential for predicting the behavior of proteins in different environments.

Polar vs. Nonpolar

Polar amino acids have side chains that can form hydrogen bonds with water, making them soluble in aqueous environments. Nonpolar amino acids, on the other hand, have hydrophobic side chains that do not interact favorably with water. This distinction is crucial for understanding protein folding and function, as the distribution of polar and nonpolar residues influences the overall structure of proteins.

Acidic, Basic, and Neutral R Groups

The R groups of polar amino acids can be further classified as acidic, basic, or neutral. Acidic amino acids have side chains that can donate protons (H+), while basic amino acids can accept protons. Neutral amino acids do not have a charge at physiological pH. This classification impacts the amino acids' roles in enzyme activity, protein stability, and interactions with other biomolecules.