Give reasons for any three of the following observations:
a) The pentaacetate of glucose does not react with hydroxylamine.
b) Amino acids behave like salts.
c) Water-soluble vitamins must be taken regularly in the diet.
d) The two strands in DNA are complementary to each other.
a) The pentaacetate of glucose does not react with hydroxylamine.
b) Amino acids behave like salts.
c) Water-soluble vitamins must be taken regularly in the diet.
d) The two strands in DNA are complementary to each other.
Solution
(a) In the pentaacetate even the anomeric –OH is acetylated: the ring cannot open, no free –CHO ever appears, so NHOH has nothing to react with.
(b) Amino acids exist as dipolar zwitterions (HN–CHR–COO) — ionic attraction gives them salt-like high melting points and water solubility.
(c) Being water-soluble, vitamins B and C are readily excreted in urine and cannot be stored — a regular dietary supply is essential.
(d) Hydrogen bonding allows only A···T and G···C pairs, so each strand's sequence fixes its partner's — the strands are complementary.
(b) Amino acids exist as dipolar zwitterions (HN–CHR–COO) — ionic attraction gives them salt-like high melting points and water solubility.
(c) Being water-soluble, vitamins B and C are readily excreted in urine and cannot be stored — a regular dietary supply is essential.
(d) Hydrogen bonding allows only A···T and G···C pairs, so each strand's sequence fixes its partner's — the strands are complementary.
CBSE Class 12 Board · 2023 · Subjective