Q.Disaccharide is -
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Classification of Carbohydrates
Carbohydrates are polyhydroxy aldehydes/ketones (or compounds that yield them on hydrolysis). They are classified by the number of simple-sugar units released on hydrolysis:
- Monosaccharides — cannot be hydrolysed further, e.g. glucose, fructose, ribose, rhamnose. Glucose reacting with HI on prolonged heating gives n-hexane, proving its straight six-carbon chain.
- Oligosaccharides (2–10 units), chiefly disaccharides such as sucrose, maltose and lactose, which hydrolyse to their monosaccharides. Concentrated H2SO4 dehydrates sucrose completely to a black mass of carbon.
- Polysaccharides — many units linked by glycosidic bonds; these are non-sweet, usually water-insoluble storage/structural molecules. Starch is a mixture of linear amylose (α-1,4 linkages, ~15–20 %, water-soluble) and branched amylopectin (α-1,4 and α-1,6). Glycogen is a highly branched animal storage polysaccharide, and cellulose is a linear β-1,4 structural polymer. …
A disaccharide yields exactly two monosaccharide units on hydrolysis, distinguishing it from a single sugar unit (monosaccharide) or a long polymer chain of many units (polysaccharide). …
A disaccharide yields exactly two monosaccharide units on hydrolysis; among the options only sucrose fits.
- Glucose and Fructose are themselves monosaccharides (single sugar units), not disaccharides.
- Starch is a polysaccharide (many glucose units joined together). …
Showing the 12 most recent of 23 on this concept.
- CBSE 2026Set ANNUAL1 markMCQQ.Polysaccharide is(a) Ribose(b) Lactose(c) Sucrose(d) Glycogen
›Reveal solutionSolution
Polysaccharides are polymers of many monosaccharide units joined by glycosidic bonds.
- Ribose: a 5-carbon monosaccharide (aldopentose).
- Lactose: a disaccharide of glucose + galactose.
- Sucrose: a disaccharide of glucose + fructose. …
- CBSE 2026Set ANNUAL1 markMCQQ.Which of the following is an Aldohexose?(a) Cellulose(b) Sucrose(c) Raffinose(d) Glucose
›Reveal solutionSolution
An aldohexose is a simple six-carbon sugar (monosaccharide) that carries an aldehyde (-CHO) functional group; glucose is the most common example.
Glucose has the molecular formula C6H12O6, with a straight-chain structure carrying an aldehyde group at C1 and hydroxyl groups on the remaining carbons - so it is classified as an aldohexose ('aldo' for the aldehyde group, 'hexose' for six carbons).
- Cellulose is a polysaccharide (polymer of many glucose units), not a monosaccharide. …
- CBSE 2025Set JZ1 markMCQQ.Sweetest sugar is :(a) Glucose(b) Lactose(c) Sucrose(d) Fructose
›Reveal solutionSolution
Fructose is the sweetest naturally occurring sugar — option (d).
Concept. Sweetness is compared on a relative scale taking table sugar (sucrose) as the reference, 100.
Relative sweetness of the options:
- Glucose ≈ 74
- Lactose ≈ 16 (least sweet)
- Sucrose = 100 (reference) …
- CBSE 2025Set D1 markMCQQ.Which of the following is a disaccharide?(a) Sucrose(b) Glucose(c) Fructose(d) Starch
›Reveal solutionSolution
Disaccharides give two monosaccharide units on hydrolysis; sucrose (glucose + fructose) is the disaccharide here.
Carbohydrates are classified by the number of monosaccharide units produced on hydrolysis:
- Monosaccharides: cannot be hydrolysed further, e.g. glucose, fructose.
- Disaccharides: give two monosaccharide units on hydrolysis, e.g. sucrose, maltose, lactose.
- Polysaccharides: give many units, e.g. starch, cellulose. …
- CBSE 2025Set ANNUAL1 markMCQQ.Disaccharide is -(a) Glucose(b) Fructose(c) Sucrose(d) Starch
›Reveal solutionSolution
A disaccharide yields exactly two monosaccharide units on hydrolysis; among the options only sucrose fits.
- Glucose and Fructose are themselves monosaccharides (single sugar units), not disaccharides.
- Starch is a polysaccharide (many glucose units joined together). …
- CBSE 2025Set ANNUAL1 markMCQQ.Which of the following monosaccharides is a ketohexose?(a) Glucose(b) Galactose(c) Fructose(d) Mannose
›Reveal solutionSolution
Monosaccharides are classified by their carbonyl group as either aldoses (aldehyde) or ketoses (ketone); among the options, fructose is the ketohexose.
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- CBSE 2024Set FZ1 markMCQQ.The compound which is not a disaccharide is:(a) Sucrose(b) Cellulose(c) Lactose(d) Maltose
›Reveal solutionSolution
Cellulose is a polysaccharide, not a disaccharide → option (b).
Concept. Carbohydrates are classified by how many monosaccharide units they release on hydrolysis: a disaccharide gives two, a polysaccharide gives many.
Checking each option.
- Sucrose → glucose + fructose (disaccharide)
- Lactose → glucose + galactose (disaccharide) …
- CBSE 2024Set D1 markMCQQ.Which of the following is a ketohexose?(a) Glucose(b) Fructose(c) Sucrose(d) Starch
›Reveal solutionSolution
Fructose = 6 carbons + keto group = ketohexose.
A ketohexose has six carbon atoms (hexose) and a ketone functional group.
- Glucose is an aldohexose (aldehyde group, 6 C).
- Fructose is a ketohexose (keto group at C-2, 6 C). …
- CBSE 2024Set ANNUAL1 markMCQQ.Glucose is -(a) An aldopentose(b) A ketopentose(c) An aldohexose(d) A ketohexose
›Reveal solutionSolution
Glucose has the molecular formula C6H12O6, with an aldehyde group at C-1, making it an aldohexose.
Sugars are classified by (i) the number of carbon atoms (tri-, tetr-, pent-, hex- ose, etc.) and (ii) the type of carbonyl group present (aldo- for -CHO, keto- for C=O within the chain). …
- CBSE 2024Set ANNUAL1 markMCQQ.Milk sugar is -(a) Sucrose(b) Lactose(c) Maltose(d) Galactose
›Reveal solutionSolution
Lactose, often called 'milk sugar', is the principal sugar naturally present in mammalian milk.
Lactose is a disaccharide formed by a glycosidic (beta-1,4) linkage between a molecule of galactose and a molecule of glucose; it occurs naturally in milk (about 4-5% in cow's milk).
Sucrose ('cane/table sugar') is glucose + fructose, obtained from sugarcane/sugar beet, not milk. …
- CBSE 2024Set ANNUAL1 markMCQQ.Glucose and fructose are(a) Isomers of each other(b) Homologus of each other(c) Anomers of each other(d) Enantioners of each other
›Reveal solutionSolution
Glucose and fructose both have the molecular formula C6H12O6 but differ in the position of the carbonyl group (glucose = aldehyde at C1, fructose = ketone at C2), making them structural (functional) isomers, not anomers or enantiomers of one another.
Glucose is an aldohexose (has a -CHO group at C1). Fructose is a ketohexose (has a C=O group at C2). Both share the same molecular formula C6H12O6, but their functional group and connectivity differ - this is the definition of (structural) isomerism.
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- CBSE 2024Set ANNUAL1 markQ.Complete the following. Amylopectin is a polymer of ______.
›Reveal solutionSolution
Amylopectin, a component of starch, is a branched polysaccharide built entirely from alpha-D-glucose monomers.
Starch is a polysaccharide made of two components: amylose (linear, alpha-1,4 glycosidic linkages) and amylopectin (branched).
Amylopectin is a branched-chain polymer of alpha-D-glucose in which glucose units are joined by: …
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