Monosaccharides are carbohydrates which cannot be hydrolysed into simpler molecules. Those containing an aldehyde group are called aldoses while those containing a keto group are called ketoses. The aldehyde group is present at C1 while the keto group is usually present at C2. All monosaccharides reduce Tollens’ reagent as well as Fehling’s solution and hence are called reducing sugars. Glucose has a six-membered cyclic structure called the pyranose structure, while fructose in sucrose has a five-membered cyclic structure called the furanose structure. During ring formation, C1 of glucose becomes chiral, and hence glucose exists in two cyclic forms called the α-anomer and the β-anomer. When two molecules of the same or different monosaccharides combine through a glycosidic linkage, a disaccharide is formed.
Match List-I with List-II.
| List-I (Monosaccharide) | List-II (Description) |
|---|---|
| (A) Glucose | (I) Aldopentose present in nucleic acids |
| (B) Fructose | (II) Compound with which the D or L configuration of carbohydrates is related |
| (C) Glyceraldehyde | (III) Aldohexose also known as dextrose |
| (D) D-Ribose | (IV) Laevorotatory ketohexose of the D-series |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A-III, B-IV, C-II, D-I
Monosaccharides are named from their functional group (aldose or ketose) and their number of carbon atoms. Their configuration, D or L, is fixed by comparing them with glyceraldehyde.
(A) Glucose — This matches (III) Aldohexose also known as dextrose. Glucose has six carbon atoms and an aldehyde group, and is dextrorotatory, D-(+)-glucose.
(B) Fructose — This matches (IV) Laevorotatory ketohexose of the D-series. Fructose has a keto group at C2; it is written D-(−)-fructose.
(C) Glyceraldehyde — This matches (II) Compound with which the D or L configuration of carbohydrates is related. Glyceraldehyde has one asymmetric carbon; sugars that can be correlated with D-(+)-glyceraldehyde are given the D-configuration, and those correlated with its L-(−) isomer the L-configuration.
(D) D-Ribose — This matches (I) Aldopentose present in nucleic acids. D-Ribose and 2-deoxy-D-ribose are the five-carbon aldoses found in nucleic acids.
NCERT (2026-27 edition):
10.1.2.1 Glucose – “Glucose is an aldohexose and is also known as dextrose.”
“…In the case of carbohydrates, this refers to their relation with a particular isomer of glyceraldehyde. Glyceraldehyde contains one asymmetric carbon atom and exists in two enantiomeric forms…”
10.1.2.2 Fructose – “Fructose is an important ketohexose.” … “It belongs to D-series and is a laevorotatory compound. It is appropriately written as D-(–)-fructose.”
10.1.5 Importance of Carbohydrates – “Two aldopentoses viz. D-ribose and 2-deoxy-D-ribose … are present in nucleic acids.”