Give a detailed account of the classification of carbohydrates into monosaccharides, oligosaccharides and polysaccharides, describing the structure, linkage and biological role of starch, glycogen and cellulose in particular.

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Carbohydrates are classified into three groups by the number of monosaccharide units they contain. Monosaccharides are the simplest carbohydrates -- single sugar units, further sorted by carbon number (triose to hexose) and by whether their carbonyl group is an aldehyde or a ketone -- with glucose (C6H12O6) as the most important example, serving as the universal respiratory fuel. Oligosaccharides contain a small number, typically two to ten, of monosaccharide units joined by glycosidic bonds; the most familiar are the disaccharides sucrose (glucose + fructose), maltose (glucose + glucose) and lactose (glucose + galactose). Polysaccharides are long polymers of many monosaccharide units, divided into homopolysaccharides (a single repeating monomer) and heteropolysaccharides (more than one monomer type). …

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2026Set ANNUAL1 markMCQ
$Q. Chitin is a linear polymer of ________ joined together by beta-1,4 glycosidic linkages.$
(a) alpha-1,4-glucan malto hydrolase
(b) beta-D-glucose units
(c) D-glycuronic acid
(d) N-acetyl-D-glucosamine units
›Reveal solutionSolution

Chitin is built from repeating N-acetyl-D-glucosamine monomers joined by beta-1,4 glycosidic linkages.

Chitin is a structural homopolysaccharide, chemically very similar in architecture to cellulose (which is a beta-1,4-linked chain of plain D-glucose units), but chitin's repeating monomer is instead N-acetyl-D-glucosamine — a glucose derivative in which the hydroxyl group at carbon-2 is replaced by an acetylated amino group (-NHCOCH3). This substitution allows chitin to form very strong hydrogen-bonded microfibrils, which is why it makes such a tough structural material (fungal cell walls, insect and crustacean exoskeletons). The other options are the monomers/hydrolytic components of different molecul …

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CBSE 2025Set ANNUAL1 markMCQ
$Q. The β-D Glucose units in cellulose are linked together by:$
(a) 1→3 Linkage.
(b) N-acetyl side chains.
(c) β-(1, 4) glycosidic Linkage.
(d) N-acetyl D-Glucosamine.
›Reveal solutionSolution

Cellulose is a homopolysaccharide of β-D-glucose units, and the glucose monomers are linked together specifically by β-(1→4) glycosidic bonds, giving it a straight, unbranched, highly hydrogen-bonded chain.

Cellulose is the chief structural polysaccharide of plant cell walls. It is built entirely of D-glucose units in the β-anomeric configuration, joined by glycosidic bonds between carbon-1 of one glucose unit and carbon-4 of the next — hence a β-(1→4) linkage.

…

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CBSE 2024Set ANNUAL1 markMCQ
$Q. The linkage present in Lactose is _____.$
(a) α, β -1, 2 - glycosidic linkage
(b) α -1, 4 - glycosidic linkage
(c) β -1, 4 - glycosidic linkage
(d) α -1, 4 - glycosidic linkage
›Reveal solutionSolution

Lactose = galactose + glucose joined by a $\beta$ -1,4-glycosidic bond.

Lactose is a disaccharide made of one unit of $\beta$ -D-galactose and one unit of $\beta$ -D-glucose. The two monosaccharides are joined through their C-1 (of galactose, $\beta$ -configuration) and C-4 (of glucose) carbons, i.e. a $\beta$ -1,4-g …

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CBSE 2023Set ANNUAL1 markMCQ
$Q. The glycosidic linkage present in maltose is _______.$
(a) $\alpha,\beta$ -1,2-glycosidic linkage
(b) $\alpha$ -1,4-glycosidic linkage
(c) $\beta$ -1,4-glycosidic linkage
(d) $\alpha$ -1,6-glycosidic linkage
›Reveal solutionSolution

Maltose is two $\alpha$ -D-glucose units joined between C1 of one and C4 of the other.

Maltose is a disaccharide made of two $\alpha$ -D-glucopyranose units linked through an $\alpha$ -1,4-glycosidic bond — the anomeric (C1, $\alpha$ -configured) carbon of one glucose unit is joined via an oxygen bridge to the C …

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CBSE 2018Set ANNUAL1 mark
$H_2SO_4$
›Reveal solutionSolution

Concentrated sulphuric acid removes the elements of water from sucrose, charring it to carbon.

Concentrated sulphuric acid is a powerful dehydrating agent. On sugar (sucrose, $C_{12}H_{22}O_{11}$ ), it removes water (in the ratio corresponding to the empirical formula, effectively $H_2O$ units) from the sugar molecule, leaving behind a black, porous mass of elemental carbon and releasing heat and steam/gases …

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CBSE 2018Set ANNUAL1 markMCQ
$Q. The number of primary and secondary hydroxyl groups in ribose are —$
(a) 1, 3
(b) 2, 3
(c) 3, 1
(d) 3, 2
›Reveal solutionSolution
Ribose's open-chain form has OH on C2/C3/C4 (secondary) and C5 (primary).

The open-chain structure of ribose (an aldopentose) is $CHO-CHOH-CHOH-CHOH-CH_2OH$ (C1 to C5).

C1 bears the aldehyde group ( $-CHO$ ), no $-OH$ here.

C2, C3, C4 each bear a hydroxyl on a carbon attached to two other carbons — these are secondary hydroxyls (3 in total). …
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Q.Give a detailed account of the classification of carbohydrates into monosaccharides, oligosaccharides and polysaccharides, describing the structure, linkage and biological role of starch, glycogen and cellulose in particular.

Concept understanding — Carbohydrates

Q.Give a detailed account of the classification of carbohydrates into monosaccharides, oligosaccharides and polysaccharides, describing the structure, linkage and biological role of starch, glycogen and cellulose in particular.

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