Question

use the diagram of the molecular structure of an amino acid to answer the question.
amino acids
diagram of amino acid molecular structure
which option explains why this amino acid can act as both an acid and a base?
(1 point)

• it contains both an amino functional group and a methyl functional group. in a solution, the amino group can decrease acidity, while the methyl group can increase acidity.
• it contains both an amino functional group and a carboxyl functional group. in a solution, the amino group can decrease acidity, while the carboxyl group can increase acidity.
• it contains both an amino functional group and a methyl functional group. in a solution, the amino group can increase acidity, while the methyl group can decrease acidity.
• it contains both an amino functional group and a carboxyl functional group. in a solution, the amino group can increase acidity, while the carboxyl group can decrease acidity.

Explanation:

1. Recall the structure of an amino acid: It has an amino group ($-NH_2$) and a carboxyl group ($-COOH$).
2. Analyze the acidic and basic properties: The amino group ($-NH_2$) can accept a proton (act as a base, decreasing acidity by removing $H^+$ from solution), and the carboxyl group ($-COOH$) can donate a proton (act as an acid, increasing acidity by releasing $H^+$).
3. Evaluate the options:

• Option 1: Methyl group is not present in the standard amino acid structure, eliminate.
• Option 2: Matches the structure (amino and carboxyl groups) and their acid - base behavior (amino decreases acidity, carboxyl increases acidity).
• Option 3: Methyl group is incorrect, and the acid - base behavior of amino and methyl groups is wrong, eliminate.
• Option 4: The acid - base behavior of amino and carboxyl groups is reversed, eliminate.

Answer:

B. It contains both an amino functional group and a carboxyl functional group. In a solution, the amino group can decrease acidity, while the carboxyl group can increase acidity