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JEE Main · 2012 · 29 Apr 2012 · Offline · Biomolecules

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Which one of the following statements is correct ?
  1. (A)All amino acids except lysine are optically active
  2. (B)All amino acids are optically active
  3. (C)All amino acids except glycine are optically active✓ Correct
  4. (D)All amino acids except glutamic acid are optically active

Answer: (C)

Solution

Optical activity needs a carbon bonded to four different groups. In the general amino acid the central carbon carries an amino group, a carboxyl group, a hydrogen and the side chain — four different groups — so it is chiral. The one exception is glycine, where leaves the central carbon with two hydrogens; it is not chiral and so is optically inactive. Every amino acid except glycine is therefore optically active.

JEE Main · 2012 · 29 Apr 2012 · Offline · Single correct option

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