Q1. What is the term for an amino acid form that has both a positively charged amino group and a negatively charged carboxylate group?

Background

Topic: Amino Acids and Their Ionic Forms

This question tests your understanding of the chemical structure of amino acids, specifically how they exist in solution at physiological pH. It focuses on the terminology used to describe the form in which both the amino group and the carboxyl group are ionized.

Key Terms and Concepts

• Amino Group (–NH2): Can accept a proton to become –NH3+ (positively charged).

• Carboxyl Group (–COOH): Can lose a proton to become –COO– (negatively charged).

• Zwitterion: A molecule with both positive and negative charges, but overall electrically neutral.

Step-by-Step Guidance

1. Recall that amino acids contain both an amino group and a carboxyl group attached to the central (alpha) carbon.

2. At physiological pH (around 7), the amino group tends to gain a proton, becoming , while the carboxyl group loses a proton, becoming .

3. Think about what it means for a molecule to have both a positive and a negative charge at the same time, but still be overall neutral.

4. Review the definitions of the answer choices: enantiomer, zwitterion, peptide, and isomer. Which one describes a molecule with both charges?

Try solving on your own before revealing the answer!