Chapter 9: Biomolecules – MCQs with Answers & Explanations
CBSE Class 11 Biology MCQs – Biomolecules (Chapter 9 | NCERT)
CBSE Class 11 Biology Chapter 9 Biomolecules: 50 MCQs with Answers and Detailed Explanations (NCERT)
Course Details (Systematic Format)
Course: CBSE Class 11 Biology
Unit: III – Cell Structure and Function
Chapter: 9 – Biomolecules
Based on: NCERT Syllabus
Examination: CBSE Board Examination (Class XI)
Assessment Focus: Conceptual clarity, chemical nature, structures, and applications
Section A: Carbohydrates (MCQs 1–10)
Q1. Which of the following is a reducing sugar?
A. Sucrose
B. Starch
C. Glucose
D. Cellulose
Answer: C
Explanation:
Glucose has a free aldehyde group in its open-chain form, enabling it to act as a reducing sugar.
Q2. The general formula of carbohydrates is:
A. (CH₂O)ₙ
B. (CHO)ₙ
C. (C₂H₄O)ₙ
D. (CH₃O)ₙ
Answer: A
Explanation:
Most carbohydrates follow the empirical formula (CH₂O)ₙ, indicating carbon, hydrogen, and oxygen in a 1:2:1 ratio.
Q3. Which polysaccharide is a major structural component of plant cell walls?
A. Starch
B. Glycogen
C. Cellulose
D. Chitin
Answer: C
Explanation:
Cellulose, made of β-glucose units, provides rigidity and strength to plant cell walls.
Q4. The glycosidic linkage in sucrose is:
A. α-1,4
B. β-1,4
C. α-1,2
D. β-1,6
Answer: C
Explanation:
Sucrose has an α-1,2 glycosidic bond between glucose and fructose.
Q5. Which carbohydrate does NOT react with iodine?
A. Starch
B. Amylose
C. Cellulose
D. Glycogen
Answer: C
Explanation:
Cellulose lacks the helical structure required to form a colored complex with iodine.
Q6. Which carbohydrate is stored in animal liver and muscles?
A. Starch
B. Glycogen
C. Cellulose
D. Sucrose
Answer: B
Explanation:
Glycogen is the storage polysaccharide in animals, providing quick energy.
Q7. Which sugar is a ketohexose?
A. Glucose
B. Ribose
C. Fructose
D. Galactose
Answer: C
Explanation:
Fructose contains a ketone functional group and six carbon atoms.
Q8. Chitin is composed of:
A. β-glucose
B. α-glucose
C. N-acetylglucosamine
D. Ribose
Answer: C
Explanation:
Chitin is a nitrogen-containing polysaccharide made of N-acetylglucosamine units.
Q9. Which carbohydrate is non-reducing?
A. Glucose
B. Maltose
C. Lactose
D. Sucrose
Answer: D
Explanation:
Sucrose has no free aldehyde or ketone group, making it non-reducing.
Q10. Cellulose differs from starch mainly due to:
A. Molecular formula
B. Type of monosaccharide
C. Glycosidic bond
D. Solubility
Answer: C
Explanation:
Cellulose has β-1,4 bonds, while starch has α-1,4 bonds, affecting digestibility.
Section B: Proteins (MCQs 11–20)
Q11. Proteins are polymers of:
A. Fatty acids
B. Nucleotides
C. Amino acids
D. Sugars
Answer: C
Explanation:
Proteins consist of amino acids linked by peptide bonds.
Q12. The bond between two amino acids is called:
A. Glycosidic bond
B. Hydrogen bond
C. Peptide bond
D. Phosphodiester bond
Answer: C
Explanation:
A peptide bond forms via condensation between amino and carboxyl groups.
Q13. The primary structure of a protein refers to:
A. Folding pattern
B. Amino acid sequence
C. Shape of active site
D. Association of subunits
Answer: B
Explanation:
Primary structure is the linear sequence of amino acids.
Q14. Which level of protein structure is stabilized by hydrogen bonds?
A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Answer: B
Explanation:
α-helices and β-sheets are stabilized by hydrogen bonds.
Q15. Keratin is an example of:
A. Globular protein
B. Enzyme
C. Fibrous protein
D. Hormone
Answer: C
Explanation:
Keratin is structural, insoluble, and fibrous in nature.
Q16. Protein denaturation results in loss of:
A. Peptide bonds
B. Primary structure
C. Secondary and tertiary structure
D. Amino acids
Answer: C
Explanation:
Denaturation disrupts folding without breaking peptide bonds.
Q17. Essential amino acids are those that:
A. Are synthesized in the body
B. Must be obtained from diet
C. Are non-functional
D. Are toxic
Answer: B
Explanation:
Humans cannot synthesize essential amino acids.
Q18. Enzymes are mostly:
A. Carbohydrates
B. Lipids
C. Proteins
D. Nucleic acids
Answer: C
Explanation:
Most enzymes are protein in nature.
Q19. The tertiary structure of a protein is stabilized by:
A. Peptide bonds only
B. Hydrogen bonds only
C. Weak interactions and disulfide bonds
D. Glycosidic bonds
Answer: C
Explanation:
Multiple interactions stabilize the three-dimensional folding.
Q20. Hemoglobin is classified as:
A. Fibrous protein
B. Structural protein
C. Globular protein
D. Storage protein
Answer: C
Explanation:
Hemoglobin is a soluble, functional globular protein.
Section C: Lipids (MCQs 21–30)
Q21. Lipids are insoluble in:
A. Ether
B. Chloroform
C. Water
D. Benzene
Answer: C
Explanation:
Lipids are hydrophobic and insoluble in water.
Q22. A triglyceride consists of:
A. Three glycerols and one fatty acid
B. One glycerol and three fatty acids
C. Two glycerols and two fatty acids
D. One glycerol and one fatty acid
Answer: B
Explanation:
Triglycerides are formed from glycerol and three fatty acids.
Q23. Unsaturated fatty acids contain:
A. No hydrogen
B. Only single bonds
C. One or more double bonds
D. Nitrogen
Answer: C
Explanation:
Double bonds cause kinks, making them liquid at room temperature.
Q24. The major component of cell membranes is:
A. Triglycerides
B. Steroids
C. Phospholipids
D. Waxes
Answer: C
Explanation:
Phospholipids form the bilayer of membranes.
Q25. Cholesterol is a type of:
A. Fatty acid
B. Phospholipid
C. Steroid
D. Wax
Answer: C
Explanation:
Cholesterol belongs to the steroid group of lipids.
Q26. Lipids provide more energy than carbohydrates because they:
A. Are soluble
B. Contain more oxygen
C. Have more C–H bonds
D. Are polymers
Answer: C
Explanation:
More C–H bonds release greater energy upon oxidation.
Q27. Waxes mainly function in:
A. Energy storage
B. Waterproofing
C. Enzyme action
D. Protein synthesis
Answer: B
Explanation:
Waxes protect surfaces from water loss.
Q28. Which lipid is abundant in seeds?
A. Phospholipids
B. Waxes
C. Triglycerides
D. Steroids
Answer: C
Explanation:
Seeds store energy mainly as triglycerides.
Q29. Which lipid maintains membrane fluidity?
A. Wax
B. Cholesterol
C. Glycogen
D. Starch
Answer: B
Explanation:
Cholesterol stabilizes membranes at varying temperatures.
Q30. Lipids are not considered polymers because:
A. They are insoluble
B. They lack repeating monomers
C. They contain hydrogen
D. They are hydrophobic
Answer: B
Explanation:
Lipids do not consist of repeating structural units.
Section D: Nucleic Acids (MCQs 31–40)
Q31. The basic unit of nucleic acids is:
A. Amino acid
B. Nucleotide
C. Nitrogen base
D. Sugar
Answer: B
Explanation:
Nucleotides polymerize to form nucleic acids.
Q32. DNA contains the sugar:
A. Ribose
B. Glucose
C. Deoxyribose
D. Fructose
Answer: C
Q33. RNA differs from DNA in having:
A. Thymine
B. Double strands
C. Ribose sugar
D. Deoxyribose sugar
Answer: C
Q34. The bond linking nucleotides is:
A. Peptide bond
B. Glycosidic bond
C. Phosphodiester bond
D. Hydrogen bond
Answer: C
Q35. Adenine pairs with thymine by:
A. One hydrogen bond
B. Two hydrogen bonds
C. Three hydrogen bonds
D. Covalent bond
Answer: B
Q36. Which nitrogenous base is absent in RNA?
A. Adenine
B. Cytosine
C. Guanine
D. Thymine
Answer: D
Q37. Purines include:
A. Adenine and guanine
B. Cytosine and thymine
C. Uracil and cytosine
D. Thymine and guanine
Answer: A
Q38. The backbone of DNA consists of:
A. Sugar and base
B. Base and phosphate
C. Sugar and phosphate
D. Only sugar
Answer: C
Q39. DNA functions mainly in:
A. Energy storage
B. Protein synthesis
C. Genetic information storage
D. Membrane formation
Answer: C
Q40. Genome refers to:
A. Set of proteins
B. Complete genetic material
C. RNA molecules
D. Cell organelles
Answer: B
Section E: Enzymes & Metabolism (MCQs 41–50)
Q41. Enzymes increase reaction rate by:
A. Increasing temperature
B. Lowering activation energy
C. Being consumed
D. Producing energy
Answer: B
Q42. The region where substrate binds is called:
A. Allosteric site
B. Active site
C. Cofactor
D. Apoenzyme
Answer: B
Q43. Optimum pH for most enzymes is:
A. 2
B. 5
C. 7
D. 9
Answer: C
Q44. Lock-and-key model explains:
A. Enzyme synthesis
B. Enzyme specificity
C. Protein denaturation
D. ATP synthesis
Answer: B
Q45. Metabolism includes:
A. Only catabolism
B. Only anabolism
C. Both anabolism and catabolism
D. Only digestion
Answer: C
Q46. ATP is known as:
A. Genetic material
B. Energy currency
C. Enzyme
D. Hormone
Answer: B
Q47. Feedback inhibition is caused by:
A. Substrate
B. Enzyme
C. End product
D. Cofactor
Answer: C
Q48. Coenzymes are usually derived from:
A. Proteins
B. Minerals
C. Vitamins
D. Carbohydrates
Answer: C
Q49. Isoenzymes differ in:
A. Function
B. Reaction catalysed
C. Structure
D. Substrate
Answer: C
Q50. Enzymes are reusable because they:
A. Are consumed
B. Remain unchanged after reaction
C. Break substrates
D. Store energy
Answer: B
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