An amino acid is described as amphoteric because it
Correct answer: C. contains both an acidic carboxyl group and a basic amino group, so it reacts with both acids and bases
- A. dissolves only in organic solvents
- B. contains a benzene ring
- C. contains both an acidic carboxyl group and a basic amino group, so it reacts with both acids and bases
- D. has no charge under any conditions
Explanation
The carboxyl group can donate a proton and the amino group can accept one, so an amino acid neutralises both acids and alkalis. Within a single molecule the proton transfers from one group to the other, giving the doubly charged zwitterion that exists at intermediate pH. This ionic character is why amino acids are crystalline solids with high melting points and dissolve readily in water.
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About Classification of Proteins
Proteins are classified by composition as simple, conjugated and derived proteins, and by shape as fibrous or globular proteins. The topic relates these classes to examples such as albumin, keratin, collagen, haemoglobin and casein, while distinguishing structural proteins from proteins with transport, catalytic or regulatory roles.
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