Question

Why is Arg often referred to as a basic amino acid? Which other two amino acids are also basic amino acids?

Short answer

Answer: The three basic amino acids are Arginine (Arg), Lysine (Lys), and Histidine (His). They are considered basic due to their side chains, which contain groups that can accept a proton and carry a positive charge, making them basic in nature.

Step-by-step solution

Understanding the properties of amino acids

Amino acids are the building blocks of proteins. They have an amino group (-NH2) and a carboxyl group (-COOH) in their basic structure. The properties of an amino acid are mainly determined by its side chain, which is the variable R group. It can be either neutral, acidic, or basic.

Identifying the properties of Arginine

Arginine (Arg) is an amino acid with a side chain containing a guanidinium group (-C(NH2)(NH)NH+). The guanidinium group can accept a proton and carry a positive charge, which makes it basic. Consequently, Arginine is referred to as a basic amino acid.

Identifying the other basic amino acids

There are two other amino acids with basic side chains that can accept protons and carry a positive charge: 1. Lysine (Lys) - has an epsilon-amino group (-NH3+) in its side chain. 2. Histidine (His) - has an imidazole group in its side chain, which has a nitrogen atom that can accept a proton and carry a positive charge. Thus, Lysine and Histidine are also considered basic amino acids.