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Answer the following… (Class 12 Chemistry SQP 2025-26, Q32B)

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ChemistryCBSE Class 12 · Sample paper, session 2025-26 · 5 marks · Long answer

CBSE Class 12 Chemistry sample paper 2025-26: question 32(B)

From the official CBSE sample question paper for 2025-26, section E, question 32(B), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q32(B) · 5 marks · Long answerBiomolecules

Answer the following questions:
I. Identify and give any one point of difference between the carbohydrate present in cane sugar and carbohydrate present in milk.
II. Glucose is an aldohexose and a monosaccharide. Which oxidising agent should be used to bring about oxidation of only the aldehydic group present in glucose?
III. Amino acid . Predict whether the pH of this amino acid will be >7, 7 or <7.
IV. Name the two major molecular shapes formed due to the folding of secondary structure of proteins.
V. Ashish's gums bleed frequently. The doctor's prescription mentioned that Ashish is suffering from scurvy. Help him to identify two food sources to help him recover faster.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.

Hints

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

Hint 1

For I, recall which monosaccharide units make up each disaccharide.

Hint 2

For III, count the acidic groups and the basic groups in the molecule.

Hint 3

For V, scurvy is a vitamin-deficiency disease; think of which vitamin it is and which fruits are rich in it.

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. I. Cane sugar contains sucrose, while milk contains lactose. Both are disaccharides. Difference: sucrose is made of -D-glucose and -D-fructose, whereas lactose is made of -D-galactose and -D-glucose. (Another valid difference: sucrose is a non-reducing sugar, while lactose is a reducing sugar.)

    1 mark

  2. II. Use bromine water. It is a mild oxidising agent that oxidises only the group of glucose to , giving gluconic acid: .

    1 mark

  3. III. The molecule has two groups but only one group. It is therefore an acidic amino acid, and its aqueous solution has pH < 7.

    1 mark

  4. IV. The two major shapes are the **-helix and the -pleated sheet**. Both are held in place by hydrogen bonds between and groups of the peptide chain.

    1 mark

  5. V. Scurvy is caused by a deficiency of vitamin C (ascorbic acid). Suitable food sources are citrus fruits (orange, lemon), amla and green leafy vegetables.

    1 mark

Answer: I. Sucrose (glucose + fructose) vs lactose (galactose + glucose); II. Bromine water; III. pH < 7 (acidic amino acid); IV. α-helix and β-pleated sheet; V. Vitamin C sources: citrus fruits, amla (or green leafy vegetables)

Where the marks are

  • Identifies sucrose and lactose and gives one correct difference, e.g. their monomer units (1 mark)
  • Names bromine water as the reagent (1 mark)
  • States pH < 7 with the reason (two –COOH groups, one –NH2) (1 mark)
  • Names α-helix and β-pleated sheet (1 mark)
  • Links scurvy to vitamin C and names two sources such as citrus fruits and amla (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 paperSample paper 2025-26: 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.