Answer: The pH at which the amino acid has no net charge (zwitterion).
- A The pH at which the amino acid has no net charge (zwitterion)
- B The pH at which the amino acid is fully protonated on both ends
- C The pKa value of the carboxyl group alone
- D The pH at which the amino acid shows maximum aqueous solubility
Correct answer: A. The pH at which the amino acid has no net charge (zwitterion)
Explanation: At the isoelectric point, the amino acid exists as a neutral zwitterion with equal positive and negative charges.
Two amino acids join via a condensation reaction: the carboxyl -OH of one and an amine -H of the other are eliminated as water, leaving a peptide bond (-CO-NH-) linking them into a dipeptide; repeating this builds a full protein chain.
Concept context
The chemistry of life: carbohydrates, proteins, lipids, nucleic acids, enzymes, and vitamins. Understand their structures, classification, and biological functions. Highly relevant for NEET and Class 12 board exams.