MCQs on Biomolecules – CBSE Class 12 Chemistry (NCERT Based)

Organic Chemistry | MCQs with Answers & Concept-Clearing Explanations

The following 50 Multiple Choice Questions (MCQs) are strictly aligned with the NCERT syllabus for CBSE Class 12 Chemistry.
They are arranged section-wise to comprehensively cover carbohydrates, proteins, enzymes, vitamins, nucleic acids, and hormones, with exam-oriented explanations, making them ideal for CBSE board exam preparation.

Section A: Carbohydrates – Basics & Classification

Q1. Biomolecules that serve as the primary source of energy are:

A. Proteins
B. Lipids
C. Carbohydrates
D. Vitamins

Answer: C

Explanation:
Carbohydrates like glucose provide immediate energy to living organisms.

Q2. Which of the following is a monosaccharide?

A. Sucrose
B. Lactose
C. Maltose
D. Glucose

Answer: D

Explanation:
Glucose cannot be hydrolysed further and is a monosaccharide.

Q3. The general formula of carbohydrates is:

A. Cₙ(H₂O)ₙ
B. CₙH₂ₙ
C. CₙH₂ₙO₂
D. CₙHₙOₙ

Answer: A

Explanation:
Carbohydrates are often called hydrates of carbon.

Q4. Which carbohydrate is known as milk sugar?

A. Sucrose
B. Maltose
C. Lactose
D. Glucose

Answer: C

Explanation:
Lactose is present in milk and is a disaccharide.

Q5. Which of the following is a reducing sugar?

A. Sucrose
B. Starch
C. Glucose
D. Cellulose

Answer: C

Explanation:
Glucose contains a free aldehyde group, so it is reducing.

Section B: Disaccharides & Polysaccharides

Q6. Sucrose is composed of:

A. Glucose + glucose
B. Glucose + fructose
C. Glucose + galactose
D. Fructose + galactose

Answer: B

Explanation:
Sucrose consists of α-glucose and β-fructose.

Q7. Which polysaccharide is used as storage material in plants?

A. Glycogen
B. Cellulose
C. Starch
D. Chitin

Answer: C

Explanation:
Plants store energy in the form of starch.

Q8. Glycogen is mainly stored in:

A. Brain
B. Bones
C. Liver and muscles
D. Kidneys

Answer: C

Explanation:
Glycogen is the storage polysaccharide in animals.

Q9. Cellulose differs from starch because it contains:

A. α-glucose units
B. β-glucose units
C. Fructose units
D. Galactose units

Answer: B

Explanation:
Cellulose is made of β-D-glucose linked by β-1,4 bonds.

Q10. Which polysaccharide is indigestible by humans?

A. Starch
B. Glycogen
C. Cellulose
D. Maltose

Answer: C

Explanation:
Humans lack enzymes to break β-1,4 glycosidic bonds.

Section C: Proteins & Amino Acids

Q11. Proteins are polymers of:

A. Sugars
B. Fatty acids
C. Amino acids
D. Nucleotides

Answer: C

Explanation:
Proteins are made up of amino acids linked by peptide bonds.

Q12. The functional groups present in amino acids are:

A. –CHO and –OH
B. –NH₂ and –COOH
C. –OH and –COOH
D. –NH₂ and –CHO

Answer: B

Explanation:
Amino acids contain both amino and carboxyl groups.

Q13. Amino acids exist as zwitterions because:

A. They are acidic
B. They are basic
C. They contain both positive and negative charges
D. They are neutral

Answer: C

Explanation:
Internal proton transfer creates dipolar ions (zwitterions).

Q14. The bond between two amino acids is called:

A. Glycosidic bond
B. Hydrogen bond
C. Peptide bond
D. Ester bond

Answer: C

Explanation:
A peptide bond (–CONH–) links amino acids.

Q15. Which level of protein structure is stabilized by hydrogen bonds?

A. Primary
B. Secondary
C. Tertiary
D. Quaternary

Answer: B

Explanation:
α-helix and β-pleated sheet are stabilized by hydrogen bonding.

Section D: Enzymes & Vitamins

Q16. Enzymes are chemically:

A. Carbohydrates
B. Lipids
C. Proteins
D. Nucleic acids

Answer: C

Explanation:
Most enzymes are protein catalysts.

Q17. Enzymes speed up reactions by:

A. Increasing temperature
B. Increasing pressure
C. Lowering activation energy
D. Increasing concentration

Answer: C

Explanation:
Enzymes provide an alternative reaction pathway.

Q18. Which vitamin is water soluble?

A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin C

Answer: D

Explanation:
Vitamin C is water soluble, others listed are fat soluble.

Q19. Deficiency of vitamin D causes:

A. Scurvy
B. Night blindness
C. Rickets
D. Beriberi

Answer: C

Explanation:
Vitamin D deficiency affects calcium metabolism, causing rickets.

Q20. Vitamin B₁ deficiency leads to:

A. Pellagra
B. Beriberi
C. Scurvy
D. Rickets

Answer: B

Explanation:
Vitamin B₁ (thiamine) deficiency causes beriberi.

Section E: Nucleic Acids

Q21. The basic unit of nucleic acids is:

A. Amino acid
B. Nucleotide
C. Nucleoside
D. Nitrogen base

Answer: B

Explanation:
Nucleic acids are polymers of nucleotides.

Q22. DNA contains which sugar?

A. Ribose
B. Fructose
C. Deoxyribose
D. Glucose

Answer: C

Explanation:
DNA contains 2-deoxyribose sugar.

Q23. RNA differs from DNA in having:

A. Thymine
B. Deoxyribose
C. Ribose
D. Double helix

Answer: C

Explanation:
RNA contains ribose sugar instead of deoxyribose.

Q24. Which nitrogen base is present only in RNA?

A. Adenine
B. Guanine
C. Cytosine
D. Uracil

Answer: D

Explanation:
RNA contains uracil instead of thymine.

Q25. The structure of DNA was proposed by:

A. Pauling
B. Watson and Crick
C. Mendel
D. Khorana

Answer: B

Explanation:
Watson and Crick proposed the double helix model.

Section F: Hormones & Miscellaneous Biomolecules

Q26. Hormones are:

A. Enzymes
B. Nutrients
C. Chemical messengers
D. Structural units

Answer: C

Explanation:
Hormones regulate body functions as chemical messengers.

Q27. Insulin is a:

A. Carbohydrate
B. Lipid
C. Protein hormone
D. Steroid

Answer: C

Explanation:
Insulin is a protein hormone.

Q28. Which hormone regulates blood sugar level?

A. Thyroxine
B. Adrenaline
C. Insulin
D. Estrogen

Answer: C

Explanation:
Insulin controls glucose metabolism.

Q29. Which biomolecule acts as genetic material?

A. Protein
B. Lipid
C. DNA
D. Vitamin

Answer: C

Explanation:
DNA stores and transfers genetic information.

Q30. Cholesterol belongs to which class of biomolecules?

A. Proteins
B. Lipids
C. Carbohydrates
D. Nucleic acids

Answer: B

Explanation:
Cholesterol is a steroid lipid.

Section G: NCERT-Based Mixed MCQs

Q31. Which sugar gives positive Tollen’s test?

A. Sucrose
B. Cellulose
C. Glucose
D. Starch

Answer: C

Explanation:
Glucose has a free aldehyde group.

Q32. Which polysaccharide gives blue color with iodine?

A. Cellulose
B. Glycogen
C. Starch
D. Chitin

Answer: C

Explanation:
Iodine fits into the helical structure of starch.

Q33. Essential amino acids are those which:

A. Are synthesized in the body
B. Cannot be synthesized in the body
C. Are acidic
D. Are basic

Answer: B

Explanation:
They must be obtained from diet.

Q34. Denaturation of proteins involves:

A. Breaking peptide bonds
B. Change in primary structure
C. Loss of biological activity
D. Formation of new amino acids

Answer: C

Explanation:
Denaturation disrupts secondary and tertiary structures.

Q35. Which vitamin acts as an antioxidant?

A. Vitamin A
B. Vitamin C
C. Vitamin D
D. Vitamin K

Answer: B

Explanation:
Vitamin C prevents oxidative damage.

Q36. Which base pairing occurs in DNA?

A. A–G
B. C–T
C. A–T
D. G–U

Answer: C

Explanation:
Adenine pairs with thymine via hydrogen bonds.

Q37. The linkage between nucleotides is:

A. Peptide bond
B. Glycosidic bond
C. Phosphodiester bond
D. Hydrogen bond

Answer: C

Explanation:
Nucleotides are linked by phosphodiester bonds.

Q38. Which carbohydrate is a ketose?

A. Glucose
B. Galactose
C. Fructose
D. Ribose

Answer: C

Explanation:
Fructose contains a ketone group.

Q39. Which protein is responsible for oxygen transport?

A. Insulin
B. Hemoglobin
C. Albumin
D. Keratin

Answer: B

Explanation:
Hemoglobin transports oxygen in blood.

Q40. Which disease is caused by vitamin C deficiency?

A. Beriberi
B. Rickets
C. Scurvy
D. Pellagra

Answer: C

Explanation:
Vitamin C deficiency leads to scurvy.

Q41. Which biomolecule is stored as energy reserve in animals?

A. Starch
B. Cellulose
C. Glycogen
D. Chitin

Answer: C

Explanation:
Animals store energy in glycogen.

Q42. Which nitrogen base is common to both DNA and RNA?

A. Thymine
B. Uracil
C. Adenine
D. None

Answer: C

Explanation:
Adenine is present in both DNA and RNA.

Q43. Which vitamin is fat soluble?

A. Vitamin B₁
B. Vitamin B₆
C. Vitamin C
D. Vitamin A

Answer: D

Explanation:
Vitamins A, D, E, K are fat soluble.

Q44. The pH at which amino acid exists as zwitterion is called:

A. Neutral pH
B. Isoionic point
C. Isoelectric point
D. Buffer point

Answer: C

Explanation:
At isoelectric point, net charge is zero.

Q45. Which carbohydrate is structural component of plant cell wall?

A. Starch
B. Glycogen
C. Cellulose
D. Sucrose

Answer: C

Explanation:
Cellulose provides structural strength.

Q46. Which biomolecule controls metabolic reactions?

A. Vitamins
B. Hormones
C. Enzymes
D. Carbohydrates

Answer: C

Explanation:
Enzymes regulate metabolic pathways.

Q47. Which vitamin deficiency causes night blindness?

A. Vitamin A
B. Vitamin B₂
C. Vitamin C
D. Vitamin D

Answer: A

Explanation:
Vitamin A is essential for vision.

Q48. Which biomolecule contains phosphate group?

A. Proteins
B. Lipids
C. Nucleic acids
D. Vitamins

Answer: C

Explanation:
Nucleic acids contain phosphate backbone.

Q49. Which hormone is steroid in nature?

A. Insulin
B. Thyroxine
C. Estrogen
D. Adrenaline

Answer: C

Explanation:
Estrogen is a steroid hormone.

Q50. Which biomolecule shows mutarotation?

A. Cellulose
B. Glucose
C. Starch
D. Protein

Answer: B

Explanation:
Glucose interconverts between α and β forms in solution.

✅ CBSE Exam Tip:
This MCQ set is fully NCERT-aligned, concept-focused, and ideal for Class 12 board exams, revision practice, and objective-type assessments.