What are monosaccharides?(b) Draw Zwitter ion structure of α amino acid.(c) Write name of components of the nucleotide monomers.

Answer:

(a) Monosaccharides: Carbohydrates that cannot be hydrolysed into simpler polyhydroxy aldehydes or ketones are called monosaccharides, e.g. glucose, fructose, ribose. They have the general formula C_nH_2nO_n (n = 3 to 7).

(b) Zwitter ion of an α-amino acid: H₃N⁺–CH(R)–COO^–. The α-carbon carries R, H, a protonated amino group (–NH₃⁺) and a carboxylate group (–COO^–); the proton of –COOH has moved to –NH₂, so the molecule is a dipolar ion with no net charge.

(c) Components of a nucleotide: (i) a nitrogenous base (purine: adenine, guanine; pyrimidine: cytosine, thymine or uracil), (ii) a pentose sugar (ribose in RNA, 2-deoxyribose in DNA) and (iii) a phosphate group (phosphoric acid residue).