Question

Which of the following is basic amino acid?

• A. Aspartic acid
• B. Proline
• C. Alanine
• D. Lysine

Answer 1

The correct option is D Lysine

In all amino acids two functional groups are present. One is carboxylic group and the second is an amine group. The carboxylic acid donate proton so it behaves as acid and amine has lone pair so it can accept the proton so it behaves as base.
As both acidic part and basic part are present in amino acid, so amino acid behaves as an acid as well as a base in water. It’s carboxylic part donates proton in water simultaneously the basic part gains the proton so, all over the amino acid having one carboxylic group and one amine group behaves as neutral.
In some amino acids the carboxylic acid is one but amine groups are more than one that amino acid donate one proton about gaining more than one proton so they behave as basic.
The structure of the given amino acids are as follows:

In all the given amino acids, only the lysine is one which has one carboxylic group and two amine groups, so it is the basic amino acid.
Therefore, option (a) is correct answer.