Question

Amino acids generally exist in the form of Zwitter ions.

• A. The basic - NH+3 group and acidic - COO- group
• B. Basic NH2 group and acidic - COOH group
• C. Basic - COO- group and acidic - NH+3 group
• D. Basic - NH2 and acidic - H+ group

Answer 1

The Correct Option is A

To determine the correct statement about the zwitterionic form of amino acids, let's analyze the structure and behavior of amino acids in solution.

1. Understanding Zwitterions:
A zwitterion is a molecule that contains both positive and negative charges but is overall electrically neutral. For amino acids, this occurs when:

• The carboxyl group (-COOH) loses a proton (H⁺) to become -COO⁻ (negatively charged).
• The amino group (-NH₂) gains a proton (H⁺) to become -NH₃⁺ (positively charged).

2. Analyzing the Functional Groups:
In the zwitterionic form:

• The -COO⁻ group is the acidic part (can donate H⁺ if needed).
• The -NH₃⁺ group is the basic part (can accept H⁺ if needed).

This is because: - -COO⁻ can act as an acid by accepting H⁺ to reform -COOH. - -NH₃⁺ can act as a base by donating H⁺ to reform -NH₂.

3. Evaluating the Options:

1. "Basic -COO⁻ group and acidic -NH₃⁺ group" → Incorrect. -COO⁻ is acidic, not basic.
2. "Basic NH₂ group and acidic -COOH group" → Incorrect. This describes the non-zwitterionic form.
3. "The basic -NH₃⁺ group and acidic -COO⁻ group" → Correct. This matches the zwitterion's properties.
4. "Basic -NH₂ and acidic -H⁺ group" → Incorrect. -H⁺ is not a functional group in amino acids.

4. Final Answer:
The correct statement is: The basic -NH₃⁺ group and acidic -COO⁻ group.

Therefore, the correct option is: \(\boxed{A}\)