Biomolecules — Class 12 MCQs with Answers
Class 12 CBSE Chemistry · Chapter 10
96 practice questions · 32 Easy · 32 Medium · 32 Hard · Updated
Practise the most important Class 12 CBSE Chemistry questions from Chapter 10, "Biomolecules". You get 9 timed quizzes made from 96 NCERT-based MCQs, with answers and explanations. The questions are split into 32 Easy, 32 Medium and 32 Hard. Warm up on the basics, then move on to the exam-level questions that set top scorers in CBSE & Maharashtra HSC Board exams, JEE Main, MHT-CET, JEE Advanced and NEET UG apart.
To score well in "Biomolecules", focus on reactions, key concepts and careful numericals. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This trains you to stay accurate under time pressure, as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on Biomolecules, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 12 Chemistry mastery score. 14 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
Key concepts: Biomolecules (Class 12 Chemistry)
Biomolecules covers the chemistry of carbohydrates, proteins, enzymes, vitamins and nucleic acids: the structure of glucose and its anomers, glycosidic and peptide bonds, reducing versus non-reducing sugars, the four levels of protein structure and denaturation, and how DNA and RNA store and transmit genetic information.
- Classification of carbohydrates
- Polyhydroxy aldehydes/ketones or compounds that yield them on hydrolysis: monosaccharides (glucose), disaccharides (sucrose) and polysaccharides (starch, cellulose).
- Structure of glucose
- An aldohexose (C₆H₁₂O₆); its cyclic pyranose form has a hemiacetal at C-1, and the open-chain form is confirmed by reactions with HCN, HI and acetic anhydride.
- Anomers and mutarotation
- α- and β-glucose differ only in the configuration at C-1 (anomeric carbon); in solution they interconvert, changing optical rotation — this is mutarotation.
- Glycosidic linkage
- The C–O–C bond joining two monosaccharide units (through the anomeric carbon), formed with loss of water; it links units in di- and polysaccharides.
Biomolecules — important questions & MCQs with answers (Class 12 Chemistry)
14 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 82 are timed and scored when you sign in.
- Q1Easy
Glucose formula:
A.CH₂OB.C₅H₁₀O₅C.C₁₂H₂₂O₁₁D.C₆H₁₂O₆✓ CorrectAnswer: D. C₆H₁₂O₆
Explanation: Glucose is a hexose, molecular formula C₆H₁₂O₆ — CH₂O is just its empirical (Cₙ(H₂O)ₙ) unit, C₅H₁₀O₅ fits a pentose, and C₁₂H₂₂O₁₁ is the disaccharide sucrose.
- Q2Easy
Vitamin C is chemically known as:
A.CalciferolB.RetinolC.ThiamineD.Ascorbic acid✓ CorrectAnswer: D. Ascorbic acid
Explanation: Vitamin C is ascorbic acid, whose deficiency causes scurvy; calciferol is vitamin D, retinol is vitamin A, and thiamine is vitamin B₁ — don't mix up the chemical names.
- Q3Easy
Building blocks of proteins:
A.GlucoseB.α-amino acids✓ CorrectC.LipidsD.VitaminsAnswer: B. α-amino acids
Explanation: Proteins are polymers of the 20 standard α-amino acids linked by peptide bonds; glucose, lipids and vitamins are separate biomolecule classes, not protein subunits.
- Q4Easy
Which vitamin is fat-soluble?
A.Vitamin B₁B.Vitamin D✓ CorrectC.Vitamin CD.Vitamin B₁₂Answer: B. Vitamin D
Explanation: Vitamin D is fat-soluble like A, E and K, so it's absorbed with dietary lipids and stored in the liver and fat, unlike water-soluble B₁, B₁₂ and C, which need daily replenishment.
- Q5Easy
Which of the following is a monosaccharide?
A.SucroseB.Glucose✓ CorrectC.StarchD.CelluloseAnswer: B. Glucose
Explanation: Glucose (C₆H₁₂O₆) is a single monosaccharide unit; sucrose is a disaccharide of glucose and fructose, while starch and cellulose are polysaccharides built from many glucose units.
- Q6Easy
Deficiency of vitamin A causes:
A.Night blindness (xerophthalmia)✓ CorrectB.Beri-beriC.ScurvyD.Pernicious anaemiaAnswer: A. Night blindness (xerophthalmia)
Explanation: Vitamin A (retinol) deficiency impairs the retina's rod pigment, causing night blindness and xerophthalmia; beri-beri, scurvy and pernicious anaemia trace to B₁, C and B₁₂ deficiency instead.
- Q7Medium
Sucrose hydrolyses to:
A.Glucose onlyB.Two glucoseC.Glucose + GalactoseD.Glucose + Fructose✓ CorrectAnswer: D. Glucose + Fructose
Explanation: Hydrolysis breaks sucrose's glycosidic bond into one glucose and one fructose unit; the reaction is called inversion because the optical rotation flips from dextro (+) to laevo (−).
- Q8Medium
Fat-soluble vitamins:
A.A, D, E, K✓ CorrectB.B, CC.All B groupD.NoneAnswer: A. A, D, E, K
Explanation: Vitamins A, D, E and K dissolve in fats, so they are absorbed with dietary lipids and stored in body fat and the liver, unlike water-soluble B and C vitamins, which are excreted.
- Q9Medium
The glycosidic linkage present in sucrose is:
A.α-1,4 linkageB.β-1,4 linkageC.α-1,β-2 linkage✓ CorrectD.α-1,6 linkageAnswer: C. α-1,β-2 linkage
Explanation: In sucrose, C-1 of α-D-glucose is linked to C-2 of β-D-fructose forming α,β-1,2-glycosidic linkage.
- Q10Medium
Deficiency of vitamin B₁ (thiamine) causes:
A.ScurvyB.Beri-beri✓ CorrectC.RicketsD.Pernicious anaemiaAnswer: B. Beri-beri
Explanation: Thiamine (vitamin B₁) deficiency causes beri-beri characterised by neurological and cardiac symptoms.
- Q11Medium
The glycosidic linkage present in maltose is:
A.β-1,4B.α-1,4✓ CorrectC.α-1,6D.α,β-1,2Answer: B. α-1,4
Explanation: Maltose has two α-D-glucose units joined through C-1 of one and C-4 of another (α-1,4 linkage).
- Q12Hard
Primary structure of protein refers to:
A.Sequence of amino acids✓ CorrectB.3D foldC.Subunit assemblyD.Local helixAnswer: A. Sequence of amino acids
Explanation: Primary structure is just the linear sequence of amino acids joined by peptide bonds; the 3D fold is tertiary, subunit assembly is quaternary, and α-helix/β-sheet local coiling is secondary.
- Q13Hard
DNA's sugar component:
A.RiboseB.Deoxyribose✓ CorrectC.GlucoseD.FructoseAnswer: B. Deoxyribose
Explanation: DNA's backbone sugar is 2-deoxyribose, missing the C-2 -OH that ribose (RNA's sugar) has; glucose and fructose are hexoses, not the pentose used in nucleic acids.
- Q14Hard
Mutarotation of glucose in aqueous solution refers to:
A.Conversion of D- to L-glucoseB.Cyclisation of fructoseC.Gradual change in specific rotation until equilibrium between α and β anomers is reached via open-chain form✓ CorrectD.Hydrolysis to gluconic acidAnswer: C. Gradual change in specific rotation until equilibrium between α and β anomers is reached via open-chain form
Explanation: α-D-glucopyranose (+112°) and β-D-glucopyranose (+19°) interconvert through the open-chain aldehydic form, reaching equilibrium at +52.7°.
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Start this chapter free →Biomolecules — FAQs
What are the key concepts in Class 12 Chemistry Biomolecules?+
Biomolecules covers the chemistry of carbohydrates, proteins, enzymes, vitamins and nucleic acids: the structure of glucose and its anomers, glycosidic and peptide bonds, reducing versus non-reducing sugars, the four levels of protein structure and denaturation, and how DNA and RNA store and transmit genetic information. Key ideas include Classification of carbohydrates, Structure of glucose, Anomers and mutarotation, Glycosidic linkage.
What does Class 12 Chemistry Chapter 10 (Biomolecules) cover on XamBaaz?+
It has 96 NCERT-based MCQs on "Biomolecules": 32 Easy, 32 Medium and 32 Hard. Together they make 9 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE & Maharashtra HSC Board exams, JEE Main, MHT-CET, JEE Advanced and NEET UG.
Are these "Biomolecules" questions free to practise?+
Yes. Sign in with Google to practise "Biomolecules" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "Biomolecules" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 9 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "Biomolecules" MCQs available with answers?+
Yes. 14 sample questions are shown here in full, each with the correct option and a step-by-step "Why" explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "Biomolecules" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip, the same negative marking as JEE Main, JEE Advanced and NEET UG. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from Biomolecules (Class 12 Chemistry)?+
The questions that matter most test Classification of carbohydrates, Structure of glucose, Anomers and mutarotation, Glycosidic linkage. This page shows 14 solved important MCQs with answers and explanations; all 96 questions on the chapter are available as timed quizzes once you sign in.
Is there an online quiz for Biomolecules?+
Yes — Class 12 Chemistry Biomolecules has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.