A zwitterion of an amino acid carries
- A. no charged groups
- B. a positive charge on the amino group and a negative charge on the carboxyl group at the same time
- C. two positive charges
- D. a single negative charge only
Explanation
The carboxyl group donates its proton to the amino group within the same molecule, so the ion has both charges and a net charge of zero at the isoelectric point. This internal ionisation explains why amino acids are crystalline solids with high melting points rather than the low melting organic liquids their size would suggest. They are also very soluble in water.
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