Read the passage carefully and answer the questions.

Biomolecules are the organic compounds present as an essential constituents of living organisms in different cells. The molecules are generally termed as macromolecules, which are carbohydrates, enzymes, nucleic acids, amino acids and proteins etc. Carbohydrates are classified as sugars and non-sugars include sucrose, glucose, fructose, starch and cellulose. Enzymes are coordinated with various chemical reactions in nucleic acid. Nucleic acids are found in living organisms made up of proteins and natural polymers. Two types that are generally found in biological systems are DNA and RNA nucleic acid. Amino acids are bifunctional groups of carboxyl and amino groups. Proteins are a class of biologically important compounds. They are crucial to virtually all processes in living systems. Some of them are hormones, which serve as chemical messengers that coordinate certain biochemical activities.

The zwitterionic form of amino acid is

(B)

The correct answer is Option (2) → (B)

Core Concept

Amino acids exist as zwitterions in aqueous solution where they contain both a positive and a negative charge simultaneously.

Explanation

Option A

This form has a negatively charged carboxyl group but the amino group is neutral. It lacks the positive charge required for zwitterionic nature.

Option B

This structure contains:

• Protonated amino group ($NH_3^+$) → positive charge
• Deprotonated carboxyl group ($COO^-$) → negative charge

Thus, it carries both charges simultaneously but is overall neutral. This is the zwitterionic form.

Option C

This structure contains a positive charge on the amino group but the carboxyl group remains neutral (COOH). Hence, it is not a dipolar ion.

Option D

Both amino and carboxyl groups are neutral. This is the non-ionized form of amino acid.