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NEET Biomolecules MCQs with answers

375 questions on Biomolecules for NEET 2027, 1 of them from previous NEET papers. Below are 15 to try; tap a question to see its answer and explanation.

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15 sample questions

easyNEET 2020

1. Vitamin deficiency causing Scurvy:

  1. Vitamin A
  2. Vitamin B₁₂
  3. Vitamin C
  4. Vitamin D
Show answer and explanation

Answer: (C) Vitamin C

Vitamin C (ascorbic acid) → collagen synthesis. Deficiency = scurvy.

Quick tip: A=Night blindness, B₁=Beriberi, C=Scurvy, D=Rickets, K=Bleeding.

NCERT Class 12, Chapter 14, page 408

easy

2. Which of the following cellular RNA molecules serves the specific biological role of carrying genetic information transcribed from DNA to the ribosomes for protein synthesis?

  1. tRNA (transfer RNA)
  2. mRNA (messenger RNA)
  3. rRNA (ribosomal RNA)
  4. snRNA (small nuclear RNA)
Show answer and explanation

Answer: (B) mRNA (messenger RNA)

Messenger RNA (mRNA) carries the genetic code transcribed from nuclear DNA into the cytoplasm to direct the sequence of amino acids during protein synthesis at the ribosomes. tRNA delivers specific amino acids, and rRNA forms the catalytic structural core of ribosomes.

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3. Consider the following statements regarding hormones: Statement I: Hormones act as intercellular chemical messengers and are produced in trace amounts. Statement II: Unlike enzymes, hormones are not consumed or modified during their regulatory action. In light of the above statements, choose the correct option:

  1. Both Statement I and Statement II are correct.
  2. Statement I is correct but Statement II is incorrect.
  3. Statement I is incorrect but Statement II is correct.
  4. Both Statement I and Statement II are incorrect.
Show answer and explanation

Answer: (B) Statement I is correct but Statement II is incorrect.

Statement I is correct as hormones are intercellular chemical messengers synthesized in trace amounts by endocrine glands. Statement II is incorrect because hormones are typically consumed, inactivated, or metabolically degraded after exerting their action, unlike biocatalysts (enzymes).

hard

4. Consider the following four biological molecules: I. RNA molecules that display catalytic self-splicing (ribozymes) II. Globular protein with intact tertiary conformation III. Fully heat-denatured insulin IV. Protease enzyme treated with concentrated heavy-metal salts Which of these will NOT function as an active biological catalyst?

  1. II and IV only
  2. I and III only
  3. III and IV only
  4. I, III and IV only
Show answer and explanation

Answer: (C) III and IV only

Biological catalysts (enzymes) require a specific three-dimensional conformation to bind substrates. Denatured insulin (III) has lost its native shape and is inactive. Treatment with heavy metal salts (IV) denatures proteins and precipitates them, destroying enzymatic function. In contrast, ribozymes (I) are catalytic RNAs and native globular proteins (II) possess functional catalytic sites.

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5. Given below are two statements: Assertion (A): Boiling an egg makes the liquid albumin turn into an insoluble, white opaque mass. Reason (R): Heating alters the primary structure of albumin by breaking the covalent peptide linkages. In light of the above statements, choose the correct answer:

  1. Both (A) and (R) are true and (R) is the correct explanation of (A)
  2. Both (A) and (R) are true but (R) is not the correct explanation of (A)
  3. (A) is true but (R) is false
  4. (A) is false but (R) is true
Show answer and explanation

Answer: (C) (A) is true but (R) is false

Assertion is true because heat coagulates albumin via denaturation. Reason is false because thermal denaturation affects only secondary, tertiary, and quaternary structures through disruption of hydrogen bonding and other weak forces; primary covalent peptide bonds remain completely intact.

easy

6. The number of peptide bonds in a linear peptide made of 28 amino-acid residues is:

  1. 28
  2. 27
  3. 26
  4. 29
Show answer and explanation

Answer: (B) 27

A linear chain of 28 residues has 28 − 1 = 27 peptide bonds.

hard

7. A polypeptide chain contains 120 amino acid residues. How many water molecules were eliminated during its total condensation synthesis, and how many water molecules are required for its complete enzymatic hydrolysis into free amino acids?

  1. 120 eliminated, 120 required
  2. 119 eliminated, 120 required
  3. 119 eliminated, 119 required
  4. 120 eliminated, 119 required
Show answer and explanation

Answer: (C) 119 eliminated, 119 required

For an unbranched, linear chain composed of n amino acid residues, the number of peptide bonds formed is (n - 1). Here, n = 120, so 119 peptide bonds are formed, meaning 119 molecules of H₂O are eliminated during synthesis. Similarly, exactly 119 H₂O molecules are consumed to hydrolyze all 119 peptide bonds.

medium

8. Match the Vitamin in Column-I with its primary dietary source in Column-II: Column-I: (A) Vitamin A (B) Vitamin B₁₂ (C) Vitamin C (D) Vitamin E Column-II: (I) Citrus fruits, amla (II) Vegetable oils like wheat germ oil (III) Fish liver oil, carrots (IV) Meat, fish, egg, curd

  1. (A)-(III), (B)-(I), (C)-(IV), (D)-(II)
  2. (A)-(IV), (B)-(III), (C)-(I), (D)-(II)
  3. (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
  4. (A)-(II), (B)-(IV), (C)-(I), (D)-(III)
Show answer and explanation

Answer: (C) (A)-(III), (B)-(IV), (C)-(I), (D)-(II)

Vitamin A is found abundantly in fish liver oil, carrots, butter, and milk. Vitamin B₁₂ is sourced from meat, fish, egg, and curd. Vitamin C is found in citrus fruits and amla, and Vitamin E in vegetable oils like wheat germ oil and sunflower oil.

medium

9. Water-soluble vitamins must be supplied regularly in the diet because they:

  1. Are not needed daily at all
  2. Are readily excreted in urine and cannot be stored (except B₁₂)
  3. Are stored in fat for years
  4. Are made in the body in large amounts
Show answer and explanation

Answer: (B) Are readily excreted in urine and cannot be stored (except B₁₂)

B-group vitamins and vitamin C are excreted in urine and not stored significantly (vitamin B₁₂ is an exception), so they must be taken regularly.

NCERT Class 12

easy

10. Which of the following describes the fundamental structural alteration that occurs when a globular protein undergoes denaturation?

  1. The covalent peptide bonds hydrolyse completely to regenerate free amino acids
  2. Globular coils uncoil and helixes get uncoiled, leading to the loss of secondary and tertiary structures
  3. The primary sequence is rearranged into a different sequence of identical amino acids
  4. Disulfide bonds spontaneously multiply and form rigid cross-linked quaternary complexes
Show answer and explanation

Answer: (B) Globular coils uncoil and helixes get uncoiled, leading to the loss of secondary and tertiary structures

According to NCERT, during denaturation, secondary and tertiary structures are destroyed while primary structure remains intact. The globules unfold and helices get uncoiled, causing the protein to lose its biological activity.

medium

11. Match the hormones in Column I with their correct structural/chemical class in Column II: Column I: (A) Oxytocin (B) Testosterone (C) Epinephrine (D) Cortisone Column II: (i) Steroid (ii) Amino acid derivative (iii) Polypeptide/peptide Choose the correct matching from the options given below:

  1. (A)-(ii), (B)-(i), (C)-(iii), (D)-(i)
  2. (A)-(i), (B)-(iii), (C)-(ii), (D)-(i)
  3. (A)-(iii), (B)-(ii), (C)-(i), (D)-(i)
  4. (A)-(iii), (B)-(i), (C)-(ii), (D)-(i)
Show answer and explanation

Answer: (D) (A)-(iii), (B)-(i), (C)-(ii), (D)-(i)

Oxytocin is a nonapeptide (peptide hormone), testosterone and cortisone are steroids containing the cyclopentanoperhydrophenanthrene core, and epinephrine is an amine derivative derived from tyrosine.

medium

12. Match the industrial/biological reaction in List-I with the corresponding enzyme catalyst in List-II: List-I: (P) Conversion of starch into maltose (Q) Conversion of glucose into ethanol and CO₂ (R) Conversion of milk sugar (lactose) into glucose and galactose (S) Hydrolysis of urea into ammonia and CO₂ List-II: (1) Zymase (2) Diastase (3) Urease (4) Lactase

  1. P-2, Q-1, R-4, S-3
  2. P-1, Q-2, R-4, S-3
  3. P-2, Q-4, R-1, S-3
  4. P-3, Q-1, R-4, S-2
Show answer and explanation

Answer: (A) P-2, Q-1, R-4, S-3

Diastase catalyzes the breakdown of starch into maltose. Zymase ferments glucose into ethanol and CO₂. Lactase hydrolyzes lactose into glucose and galactose, and urease decomposes urea into ammonia and carbon dioxide.

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13. During the formation of a dinucleotide from two mononucleotides, which functional groups are involved in the condensation reaction that links the two sugar units?

  1. The 5′-phosphate group of one nucleotide and the 3′-hydroxyl group of the next nucleotide
  2. The 1′-amino group of one base and the 3′-hydroxyl of the other sugar
  3. The 2′-hydroxyl group of one sugar and the 5′-phosphate of the other sugar
  4. The 3′-phosphate group of one nucleotide and the 3′-hydroxyl group of the next nucleotide
Show answer and explanation

Answer: (A) The 5′-phosphate group of one nucleotide and the 3′-hydroxyl group of the next nucleotide

Mononucleotides are linked together through phosphodiester linkages between the 5′-phosphate of one nucleotide and the 3′-hydroxyl group of the adjacent nucleotide. This condensation creates a directional 5′ → 3′ phosphodiester backbone.

medium

14. Given below are two statements: Statement I: The chemical nature of water as a polar solvent plays a passive, non-functional role in the structural organization of biomolecules. Statement II: The hydrophobic effect, driven by water molecules, is a primary driving force behind the tertiary folding of globular proteins and lipid bilayer formation.

  1. Both Statement I and Statement II are correct
  2. Statement I is correct but Statement II is incorrect
  3. Statement I is incorrect but Statement II is correct
  4. Both Statement I and Statement II are incorrect
Show answer and explanation

Answer: (C) Statement I is incorrect but Statement II is correct

Statement I is incorrect because water is actively involved in biomolecular organization, mediating hydrogen bonds and hydrophobic interactions. Statement II is correct because the clustering of non-polar residues away from aqueous solvent (hydrophobic effect) provides the entropy gain needed to stabilize protein folding and cell membranes.

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15. Which of the following carbohydrates gives a positive Fehling's test but does NOT contain any β-glycosidic linkage?

  1. Sucrose
  2. Lactose
  3. Maltose
  4. Cellobiose
Show answer and explanation

Answer: (C) Maltose

Maltose is a reducing sugar (gives a positive Fehling's test) containing an α-(1→4) glycosidic linkage between two α-D-glucose units. Lactose and cellobiose contain β-glycosidic linkages, while sucrose is non-reducing.

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