CBSE Class 12 · 2018 · BiomoleculesShort Answer

(a) — both terminal groups oxidised to –COOH.
(b) In solution an amino acid is the zwitterion H${}_3$N${}^{+}$–CHR–COO${}^{-}$: the –COO${}^{-}$ accepts protons (base) and the –NH${}_3^{+}$ donates them (acid) — hence \textbf{amphoteric}.
(c) The \textbf{α-helix} is one chain coiled on itself with intramolecular H-bonds; the \textbf{β-pleated sheet} is extended chains lying side by side bonded chain-to-chain.