Step 1: Understanding the Question:
Amino acids are classified based on the nature of their side chains. Step 3: Detailed Explanation:
- Arg (Arginine) and Lys (Lysine) are basic amino acids.
- Met (Methionine) is a neutral sulfur-containing amino acid.
- Asp (Aspartic acid) and Glu (Glutamic acid) have extra carboxylic groups in their side chains, making them acidic. Step 4: Final Answer:
Asp (Aspartic acid) is the acidic amino acid.