Question

Which of the following amino acids are negatively charged?
A. Aspartic acid
B. Lysine
C. Arginine
D. Histidine

Answer 1

Hint: The amino acids are often referred to as the building blocks of proteins. They are the compounds that play an important role in our body. They are required for vital processes like the building of proteins and the synthesis of hormones and neurotransmitters.

Complete answer: The two amino acids have acidic side chains at the neutral pH. These are the aspartic acid or the aspartate and also the glutamic acid or the glutamate. Their side chains have carboxylic acid groups whose pKa's are low enough to lose protons and then they become negatively charged during the process. These are the amphoteric compounds in which both the acidic group and a basic group are bonded to the same α-carbon atom. The one hydrogen atom and a substituent or variable R group are also attached to the α-carbon atom. The biochemical properties of the amino acid depend on the nature of the R group. For example, in some of the amino acids like the aspartic acid and the glutamic acid, the R group carries an extra carboxylic group. These amino acids are known as the acidic amino acids and are negatively charged at neutral pH due to the presence of extra carboxylic groups in the R group.
Therefore, the correct answer is option A.

Note: The amino acid plays an important role in almost every system throughout our body, such as:
•They assist in the creation and growth of the muscles, connective tissue, and skin.
•Also assist in maintaining muscle tone and tissue strength.
•They heal and repair.
•Helps in normal digestion.
•Also helps to provide energy for the body.