a. Write the products when D-Glucose reacts with Conc. HNO₃.
b. Amino acids show amphoteric character. Why?
c. Write one difference between $\mathrm{\alpha }\text{-helix }$and $\mathrm{\beta }\text{-pleated }$structures of proteins.

a. Saccharic Acid

On oxidation with nitric acid, glucose as well as gluconic acid both yield a dicarboxylic acid, saccharic acid. This indicates the presence of a primary alcoholic (–OH) group in glucose.

b. Due to formation of Zwitter ion. In zwitter ionic form, amino acids show amphoteric behavior as they react both with acids and bases. 

c. $\mathrm{\alpha }\text{-helix }$has intramolecular hydrogen bonding and $\mathrm{\beta }\text{-pleated }$structure has intermolecular hydrogen bonding.