Question

The sugar moiety present in RNA molecule is:
A ) $$\beta -D-2-$$deoxyribose
 B ) $$\beta -D-$$galactose
C ) $$\beta -D-$$fructofuranose
D ) $$\beta -D-$$ ribose
E ) $$\beta -D-3-$$ribose

Answer 1

Hint: The sugar moiety present in RNA is similar to the sugar moiety present in DNA. In DNA, $$\beta -D-2-$$deoxyribose sugar is present in which hydroxyl group at the second carbon atom is replaced with hydrogen atom. Whereas in RNA, this hydroxyl group is intact.

Complete step by step answer:
The components of one molecule of RNA are phosphoric acid, pentose sugar and nitrogen bases. Nitrogen base has cyclic structure. The sugar present in RNA is $$\beta -D-$$ ribose sugar.
The bases present in RNA are adenine, guanine, cytosine and uracil. Ribonucleoside is the combination of nitrogen base with sugar.
Ribonucleotide is the combination of ribonucleoside with phosphoric acid. Thus, ribonucleotide contains phosphoric acid, sugar and nitrogen base.

The structures of and the ribonucleotide present in RNA molecule are shown below.

The structures of $$\beta -D-2-$$deoxyribose, C ) $$\beta -D-$$fructofuranose and $$\beta -D-$$galactose are as shown below.

Hence, the option D ) $$\beta -D-$$ ribose is the correct option.

Additional information: The chemical composition of DNA is similar to that of RNA. In DNA, instead of uracil, the nitrogen base present is thymine. Also, the sugar present in RNA is $$\beta -D-$$ ribose whereas the sugar present in DNA is $$\beta -D-2-$$deoxyribose.

Note:
In the furanose form of sugar, when the hydroxyl group of anomeric carbon atom is above the plane of the paper, the configuration is $$\alpha$$. But when the hydroxyl group of anomeric carbon atoms is below the plane of the paper, the configuration is $$\beta$$. The compounds given in the options are hexose sugars. They have the same number of carbon atoms. But they differ in the configuration. Deoxy sugar contains one less oxygen atom than non deoxy sugar.