NEET Biomolecules PYQs & Practice Questions

10 free NEET Chemistry questions on Biomolecules, starting with previous year questions (2016–2026). Tap “Show answer” to check each one. No login needed.

Topics: Carbohydrates · Proteins · Enzymes and Nucleic Acids · Vitamins · Vitamin Deficiency Diseases · Carbohydrates - Identification · Polymer Stored in the Liver · Products of Sucrose Hydrolysis · Stabilising Force in the α-Helix Structure · Identifying a Vitamin Among Listed Acids · Carbon Positions Linked by a Phosphodiester Bond · Monomeric Units of Nucleic Acids

Q1NEET 2026Sodium Fusion Test for Amino Acids
The amino acid that gives a red-blood colour on treating its sodium fusion extract with sodium nitroprusside is:
- A. threonine
- B. methionine
- C. serine
- D. leucine
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Answer: A — threonine
Sodium fusion converts any organically bound sulfur present in an amino acid into sodium sulfide (Na2S). Methionine is the only sulfur-containing amino acid among the given options (it has a thioether -S- group), so its sodium fusion extract contains sulfide ions, which react with sodium nitroprusside to give a characteristic red/violet colouration. Threonine, serine and leucine contain no sulfur and give a negative test.
Q2NEET 2026Secondary Structure of Proteins
The correct statement about peptides and proteins is:
- A. Only the proteins having a quaternary structure are biologically active
- B. In β-pleated sheet structures, peptide chains are held together by intermolecular hydrogen bonds
- C. In α-helices, the polypeptide chain is twisted into a left-handed screw (helix) through intramolecular hydrogen bonds
- D. Tertiary structure of proteins has two or more polypeptide subunits.
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Answer: A — Only the proteins having a quaternary structure are biologically active
In β-pleated sheet structures, adjacent polypeptide strands are held together by hydrogen bonds formed between different chains (or different segments of an extended chain), i.e., intermolecular hydrogen bonds -- this is correct. The α-helix is actually a RIGHT-handed (not left-handed) screw, stabilized by intramolecular hydrogen bonds. Proteins without quaternary structure can still be biologically active. Two or more polypeptide subunits describes the QUATERNARY structure, not tertiary.
Q3NEET 2026Vitamins and Their Sources
Match the vitamins in List I with their sources in List II. List I: A. vitamin A, B. vitamin B12, C. vitamin E, D. vitamin K List II: I. meat, II. Sunflower oil, III. green leafy vegetables, IV. carrots Choose the correct answer from the options given below.
- A. A-IV, B-I, C-II, D-III
- B. A-IV, B-II, C-I, D-III
- C. A-III, B-I, C-IV, D-II
- D. A-II, B-III, C-IV, D-I
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Answer: —
Vitamin A is sourced from carrots (IV). Vitamin B12 is sourced from meat (I). Vitamin E is sourced from sunflower oil (II). Vitamin K is sourced from green leafy vegetables (III). So A-IV, B-I, C-II, D-III.
Q4NEET 2026Secondary structure of DNA/RNA
The correct statement with regard to the secondary structure of DNA/RNA is:
- A. DNA possesses a double strand helix structure and contains thymine as one of the four bases
- B. DNA possesses a single strand helix structure and contains uracil as one of the four bases
- C. RNA possesses a double strand helix structure and contains uracil as one of the four bases
- D. RNA possesses a single strand helix structure and contains thymine as one of the four bases
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Answer: —
DNA is a double helix containing thymine (not uracil); RNA is typically single-stranded and contains uracil (not thymine).

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Q5NEET 2025Vitamin Deficiency Diseases
Match List - I with List - II. List-I (Name of Vitamin): A. Vitamin B12, B. Vitamin D, C. Vitamin B2, D. Vitamin B6. List-II (Deficiency disease): I. Cheilosis, II. Convulsions, III. Rickets, IV. Pernicious anaemia. Choose the correct answer from the options given below :
- A. A-I, B-III, C-II, D-IV
- B. A-IV, B-III, C-I, D-II
- C. A-II, B-III, C-I, D-IV
- D. A-IV, B-III, C-II, D-I
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Answer: A — A-I, B-III, C-II, D-IV
Vitamin B12 deficiency causes pernicious anaemia (IV). Vitamin D deficiency causes rickets (III). Vitamin B2 deficiency causes cheilosis (I). Vitamin B6 deficiency causes convulsions (II). So A-IV, B-III, C-I, D-II.
Q6NEET 2025Carbohydrates - Identification
Sugar 'X': A. is found in honey. B. is a keto sugar. C. exists in α and β anomeric forms. D. is laevorotatory. 'X' is :
- A. D-Glucose
- B. D-Fructose
- C. Maltose
- D. Sucrose
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Answer: A — D-Glucose
Among the options, only D-Fructose is a keto sugar (ketohexose), is found abundantly in honey, exists in α/β anomeric forms, and is laevorotatory (also called levulose).
Q7NEET 2023Nucleosides and Nucleotides
Given below are two statements: Statement I: A unit formed by the attachment of a base to the 1' position of sugar is known as nucleoside. Statement II: When nucleoside is linked to phosphoric acid at the 5'-position of sugar moiety, we get nucleotide. In the light of the above statements, choose the correct answer from the options given below.
- A. Both Statement I and Statement II are false.
- B. Statement I is true and Statement II is false.
- C. Statement I is false and Statement II is true.
- D. Both Statement I and Statement II are true.
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Answer: C — Statement I is false and Statement II is true.
Statement I is correct: a nucleoside is formed by attachment of a nitrogenous base to the 1' position of the pentose sugar. Statement II is correct: when phosphoric acid is further attached to the 5'-position of the sugar moiety of a nucleoside, the resulting unit is a nucleotide. Both statements are true.
Q8NEET 2023Role of Minerals (Ca, Mg) in the Body
Which one of the following statements is correct? (1) All enzymes that utilise ATP in phosphate transfer require Ca as the cofactor. (2) The bone in human body is an inert and unchanging substance. (3) Mg plays roles in neuromuscular function and interneuronal transmission. (4) The daily requirement of Mg and Ca in the human body is estimated to be 0.2 - 0.3 g.
- A. All enzymes that utilise ATP in phosphate transfer require Ca as the cofactor.
- B. The bone in human body is an inert and unchanging substance.
- C. Mg plays roles in neuromuscular function and interneuronal transmission.
- D. The daily requirement of Mg and Ca in the human body is estimated to be 0.2 - 0.3 g.
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Answer: C — Mg plays roles in neuromuscular function and interneuronal transmission.
Statement 1 is incorrect — it is Mg, not Ca, that acts as a cofactor for enzymes utilising ATP in phosphate transfer. Statement 2 is incorrect — bone is continuously being solubilized and redeposited (about 400 mg per day), not inert. Statement 3 is incorrect — it is Ca, not Mg, that plays roles in neuromuscular function and interneuronal transmission. Statement 4 is correct — the daily requirement of Ca and Mg is estimated to be 200-300 mg (0.2-0.3 g).

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Q9NEET 2022Enzymes
The incorrect statement from the following:
- A. Like chemical catalysis enzymes reduce the activation energy of bio processes.
- B. Enzymes are polysaccharides.
- C. Enzymes are very specific for a particular reaction and substrate.
- D. Enzymes are biocatalysts.
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Answer: A — Like chemical catalysis enzymes reduce the activation energy of bio processes.
Enzymes are proteins, not polysaccharides. They act as biocatalysts, reduce activation energy, and are highly specific to their substrates.
Q10NEET 2022Enzymes - Nature and Function
The incorrect statement regarding enzymes is:
- A. Enzymes are biocatalysts.
- B. Like chemical catalysts enzymes reduce the activation energy of bio processes.
- C. Enzymes are polysaccharides.
- D. Enzymes are very specific for a particular reaction and substrate.
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Answer: B — Like chemical catalysts enzymes reduce the activation energy of bio processes.
Enzymes are proteins, not polysaccharides, making statement 3 incorrect. Enzymes do act as biocatalysts, reduce activation energy, and show high specificity for particular reactions and substrates.

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