Chemistry · chapter PYQs

Biomolecules, on the exam screen.

6 questions from NEET 2026, Re-NEET 2026, NEET 2020, 6 minutes, marked +4 / −1. See them with solutions.

Biomolecules · PYQs

Candidate: You

Time Left

Q1/6

Question 1 · NEET 2026 · Q51 · +4 / −1
The correct statement with regard to the secondary structure of DNA/RNA is
Answer and explanation
Answer: (2)
DNA has a double-stranded helical secondary structure (two antiparallel polynucleotide chains) and its four bases are adenine, guanine, cytosine and thymine. RNA is generally single-stranded and contains uracil in place of thymine, so only the DNA statement pairing double-strand + thymine is correct.
Question 2 · Re-NEET 2026 · Q50 · +4 / −1
The correct statement about peptides and proteins is
Answer and explanation
Answer: (3)
In a $\beta$ -pleated sheet the polypeptide chains lie stretched side by side, and the hydrogen bonds run BETWEEN neighbouring chains - intermolecular. This is the key structural contrast with the $\alpha$ -helix, where the hydrogen bonds are intramolecular, formed within a single coiled chain. NCERT Class 12, Biomolecules (secondary structure of proteins).
Question 3 · Re-NEET 2026 · Q55 · +4 / −1
The amino acid that gives a red-blood colour on treating its sodium fusion extract with sodium nitroprusside is
Answer and explanation
Answer: (3)
The sodium nitroprusside test detects SULPHUR: fusion with sodium converts organic sulphur to sulphide, which reacts with nitroprusside to give the intensely coloured complex $\mathrm{Na}_{4}[\mathrm{Fe}(\mathrm{CN})_{5}\mathrm{NOS}]$ . Of the four amino acids listed, only methionine contains sulphur - leucine is purely hydrocarbon in its side chain, while threonine and serine carry hydroxyl groups. NCERT Class 12, Biomolecules (amino acids); the detection method is from NCERT Class 11, Organic Chemistry: Some Basic Principles and Techniques.
Question 4 · Re-NEET 2026 · Q80 · +4 / −1
Match the vitamins in List I with their sources in List II.
List I
List II
P) vitamin A
I) meat
Q) vitamin $\text{B}_{12}$
II) sunflower oil
R) vitamin E
III) green leafy vegetables
S) vitamin K
IV) carrots
Choose the correct answer from the options given below.
Answer and explanation
Answer: (2)
Carrots are rich in $\beta$ -carotene, the precursor of vitamin A (P-IV). Vitamin $\text{B}_{12}$ is essentially absent from plant foods and comes from animal sources such as meat (Q-I). Vitamin E is a fat-soluble antioxidant abundant in vegetable oils including sunflower oil (R-II). Vitamin K, needed for blood clotting, is supplied mainly by green leafy vegetables (S-III). NCERT Class 12, Biomolecules (vitamins).
Question 5 · NEET 2020 · Q91 · +4 / −1
Sucrose on hydrolysis gives
Answer and explanation
Answer: (2)
Sucrose is made of an $\alpha$ -D-glucose unit and a $\beta$ -D-fructose unit joined through a glycosidic bond. On hydrolysis, this bond breaks to give glucose and fructose. The NEET 2020 keyed pair is $\alpha$ -D-glucose and $\beta$ -D-fructose.
Question 6 · NEET 2020 · Q121 · +4 / −1
Which of the following is a basic amino acid ?
Answer and explanation
Answer: (3)
Lysine is a basic amino acid due to the presence of an additional amino group ( $-\mathrm{NH}_{2}$ ) in its side chain, making it positively charged at physiological pH. Chapter: Biomolecules.

List I	List II
P) vitamin A	I) meat
Q) vitamin $\text{B}_{12}$	II) sunflower oil
R) vitamin E	III) green leafy vegetables
S) vitamin K	IV) carrots