Question

A five carbon sugar with molecular formula $C_5{H}_{10}{O}_4$
(A) Deoxyribose
(B) Ribose
(C) Glucose
(D) Lactose

Answer 1

Hint: Deoxyribose and ribose is a pentose sugar, however,glucose is a hexose sugar. Lactose sugar is a disaccharide that is made up of two sugar subunits, whereas the rest of the three options given in the question are monosaccharide.

Complete step by step answer: To answer this question, we will see one by one all the options given in the question.
Considering option (A), Deoxyribose. Deoxyribose is a five-carbon sugar molecule that helps form the phosphate backbone of DNA molecules. DNA, or deoxyribonucleic acid is a polymer formed of many nucleic acids. Its formula is $C_5{H}_{10}{O}_4$. The structure of deoxyribose is as follows:

Considering option (B),Ribose. Ribose is a simple sugar and carbohydrate with molecular formula $C_5{H}_{10}{O}_5$.The naturally occurring form, d-ribose is a component of the ribonucleotides from which RNA is built.The structure of ribose is as follows:

Considering option (C), Glucose.Glucose, also called dextrose, is a six carbon sugar molecule and one of the group of simple sugars. It has the molecular formula $C_6{H}_{10}{O}_6$. It is found in fruits and honey and is the major free sugar circulating in the blood of higher animals.
Considering option (D)Lactose.Lactose is a disaccharide. It is a sugar composed of galactose and glucose subunits and has the molecular formula $C_{12}{H}_{22}{O}_{11}$. Lactose makes up around 2-8% of milk.

Hence, the correct answer is A option.

Note: The difference in ribose and deoxyribose is the presence of the hydroxyl group on the 2’ position of the ribose and its absence on the 2’ position carbon of the deoxyribose. Each nucleic acid is composed of a Deoxyribose molecule bound to both a phosphate group and either a purine or a pyrimidine.