Question

Sugars are essential components of nucleic acids. 

a) Provide the precise chemical description (anomer, isomer and either pyranose or furanose form) of thecircular stereoisomers that are formed by ribose in cells. (0.5 marks)

b) Which circular stereoisomer (anomer, isomer and either pyranose or furanose form) is found in DNA? (0.5 marks)

c) Using the language of the unit, give an explanation whether the sugarcomponents of DNA are reducing sugars? (1 mark). (no more than 50 words; use key words).

Answer 1

a) Ribose sugars form 4 stereomers in cells-

alpha - or beta- ribopyranose with six membered ring (C2' - endo)

alpha - or beta- ribofuranose with five membered ring (C3'- endo).

b) DNA contains beta-D-2'- deoxyribose sugar. D- form of ribose sugar in DNA is an isomer of L- form of ribose sugar.

c) Deoxyribose sugar in DNA is a monosaccharide pentose sugar. All monosaccharide sugars are reducing sugars because they have either a free aldehyde or a free ketonic group that acts as a reducing agent. In DNA, deoxyribose contains a free aldehyde group hance it is reducing in nature.

Thanks!