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The maintenance functions of… (Class 10 Science 2025, Q38)

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ScienceCBSE Class 10 · Board exam 2025, set 31/1/1 · 4 marks · Case-based

CBSE Class 10 Science 2025: question 38

Set in the CBSE Class 10 board exam of 2025, paper 31/1/1, section E, question 38, for 4 marks. Try it first; the hints and our step-by-step solution are below.

Q38 · 4 marks · Case-basedCompetency-basedLife Processes

The maintenance functions of all living organisms must go on even when they are not doing anything particular. Even when we are just sitting in a class or even asleep, this maintenance job has to go on. These maintenance processes require energy to prevent damage and break-down of cells and tissues, which is obtained by the individual organism from the food prepared by the autotrophs, called producers.

  1. (a)

    Name and define the process by which green plants prepare food.

    1 mark
  2. (b)

    Write chemical equation involved in the above process.

    1 mark
  3. (c)(i)

    State in proper sequence the events that occur in synthesis of food by desert plants.

    2 marks

  4. OR

    (c)(ii)

    Explain giving reasons what happens to the rate at which the green plants will prepare food (I) during cloudy weather, and (II) when stomata get blocked due to dust.

    2 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/1/1.

Hints

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

Hint 1

What are the raw materials and products of food making in leaves?

Hint 2

Desert plants keep stomata closed during the hot day – so when do they take in CO₂?

Hint 3

For (c)(ii), ask which raw material or energy source is reduced in each case.

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) The process is photosynthesis.

    ½ mark

  2. Definition: green plants take in carbon dioxide and water and, using sunlight absorbed by chlorophyll, convert them into carbohydrates (food), releasing oxygen.

    ½ mark

  3. (b)

    1 mark

  4. (c)(i) Step 1 (night): desert plants open their stomata only at night, to reduce water loss. They take in and store it as an intermediate (an acid).

    ½ mark

  5. Step 2 (day, stomata closed): chlorophyll absorbs light energy.

    ½ mark

  6. Step 3: the light energy is converted into chemical energy, and water molecules are split into hydrogen and oxygen.

    ½ mark

  7. Step 4: the released from the stored intermediate is reduced to carbohydrates using this energy.

    ½ mark

  8. (c)(ii)(I) Cloudy weather: the rate of food preparation decreases. Less sunlight reaches the leaves, so chlorophyll absorbs less light energy for photosynthesis.

    1 mark

  9. (c)(ii)(II) Stomata blocked by dust: the rate decreases. Gaseous exchange is reduced, so less , a raw material, enters the leaf.

    1 mark

Answer: (a) Photosynthesis – making carbohydrates from CO₂ and water using sunlight and chlorophyll; (b) 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O; (c)(i) CO₂ taken in at night and stored as intermediate → light absorbed by chlorophyll in day → light energy converted to chemical energy and water split → CO₂ reduced to carbohydrate; (c)(ii) rate decreases in both: (I) less light, (II) less CO₂ intake due to reduced gaseous exchange

Where the marks are

  • Names photosynthesis (½ mark)
  • Correct definition (½ mark)
  • Correct equation (1 mark)
  • Correct sequence of events in desert plants, including night-time CO₂ uptake as an intermediate (2 marks)
  • Cloudy weather: rate decreases due to less sunlight (1 mark)
  • Blocked stomata: rate decreases due to reduced gaseous exchange/CO₂ (1 mark)

Revise the chapter

  • Chapter: Life Processes (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Life Processes, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/1/1: 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.