試題詳解

3. The uncommon amino acid selenocysteine has an R group with the structure -CH₂-SeH (pK_a ≈ 5). In an aqueous solution, pH = 7.0, selenocysteine would:
(A) be a fully ionized zwitterion with no net charge.
(B)be found in proteins as D-selenocysteine.
(C) never be found in a protein.
(D)be nonionic.
(E)not be optically active.