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Science · 2023 · 3 marks
CBSE 2023 · Region 2 · Set 1 · Q29
(a) (i) What is the first step in the breakdown of glucose during aerobic and anaerobic respiration? Where does it take place? (ii) ATP is called the…
(a)(i)
What is the first step in the breakdown of glucose during aerobic and anaerobic respiration ? Where does it take place ?
(ii)
ATP is called the energy currency of the cell. Why ?
(iii)
What is meant by "residual volume of air" in a breathing cycle ?
OR
(b)
Write in sequence the steps for experimental verification of the fact that "sunlight is essential for photosynthesis".
Marking-scheme solution
(a) (i) Glucose ⟶ Pyruvic acid /Pyruvate In the cytoplasm
(ii) It is used as fuel for all activities in a cell / ATP is broken down giving rise to a fixed amount of energy which drive endothermic reactions in the cell.
(iii) When air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for the oxygen to be absorbed and for the carbon dioxide to be released / volume of air present in lung after exhalation.
(b) • A potted plant is taken and kept in dark for $\displaystyle 24$ hrs to destarch it.
Cover a part of a leaf of the plant with black paper to prevent that area from getting sunlight.
Keep the plant in sunlight for $\displaystyle 24$ hours.
Pluck the leaf, remove the black paper, boil it in alcohol and dipthe leaf in iodine solution for starch test.
The covered part showed no change in colour indicating that starch has not been produced due to the absence of sunlight.
The rest of the leaf turned blue black proving that starch is produced during photosynthesis and sunlight is essential for that.
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CBSE Class 10 Science past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.