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(1 + 1 + 1 = 3) (Class 12 Chemistry 2025, Q28)

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ChemistryCBSE Class 12 · Board exam 2025, set 56/1/1 · 3 marks · Short answer

CBSE Class 12 Chemistry 2025: question 28

Set in the CBSE Class 12 board exam of 2025, paper 56/1/1, section C, question 28, for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q28 · 3 marks · Short answerBiomolecules

(1 + 1 + 1 = 3)

  1. (a)

    What is the difference between native protein and denatured protein ?

    1 mark
  2. (b)

    Which one of the following is a disaccharide ? Glucose, Lactose, Amylose, Fructose

    1 mark
  3. (c)

    Which vitamin is responsible for the coagulation of blood ?

    1 mark

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 56/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Denaturation affects higher levels of structure but not the peptide sequence.

Hint 2

A disaccharide gives two monosaccharide units on hydrolysis.

Hint 3

Deficiency of this vitamin increases blood-clotting time.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a) A native protein has its natural three-dimensional (secondary and tertiary) structure intact and is biologically active. In a denatured protein this structure is destroyed (only the primary structure remains), and it is biologically inactive.

    1 mark

  2. (b) Lactose is a disaccharide (β-D-galactose + β-D-glucose). Glucose and fructose are monosaccharides, and amylose is a polysaccharide.

    1 mark

  3. (c) Vitamin K is responsible for the coagulation of blood.

    1 mark

Answer: (a) Native: 3D structure intact, biologically active; denatured: 3D structure destroyed, inactive; (b) Lactose; (c) Vitamin K

Where the marks are

  • One correct difference between native and denatured protein (1 mark)
  • Lactose (1 mark)
  • Vitamin K (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Biomolecules, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 56/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.