Question

Which of the following amino acids are negatively charged?

• A. Aspartic acid
• B. Lysine
• C. Arginine
• D. Histidine

Answer 1

The correct option is A Aspartic acid

Amino acids are amphoteric compounds in which both an acidic (carboxylic) group and a basic (amino) group are bonded to same $\alpha$-carbon atom. One hydrogen atom and a substituent or variable R group are also attached to the $\alpha$-carbon atom. The biochemical properties of the amino acid depend on the nature of R group. For example, in some amino acids like aspartic acid and glutamic acid, the R group carries an extra carboxylic group. These amino acids are called acidic amino acids and are negatively charged at neutral pH because of the presence of extra carboxylic groups in R group.