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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3bm195

A mixture of glycine (pI ), aspartic acid (pI ) and lysine (pI ) is placed in a buffer at pH 4.0 for paper electrophoresis. Which statements are correct?

  1. AAspartic acid migrates toward the anode.
  2. BGlycine migrates toward the cathode.
  3. CLysine migrates toward the anode.
  4. DGlycine remains at the origin.

Answer: A, B

A species is anionic if pH > pI and cationic if pH < pI. At pH 4.0, Asp (pI 2.74) is negative and moves to the anode; Gly (pI 5.97) is positive and moves to the cathode; Lys (pI 9.74) is strongly positive and goes to the cathode. Gly does not stay at the origin since pH differs from its pI.
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