UPSC Prelims 2014 GS Paper I · Q65 of 100 General Science easy

Which one of the following is the process involved in photosynthesis?

  1. (a) Potential energy is released to form free energy
  2. (b) Free energy is converted into potential energy and stored ✓ UPSC's answer
  3. (c) Food is oxidized to release carbon dioxide and water
  4. (d) Oxygen is taken, and carbon dioxide and water vapour are given out

Why the answer is (b)

• Photosynthesis captures the free (radiant) energy of sunlight and converts it into chemical potential energy stored in glucose, using CO2 and water and releasing oxygen — option (b).

• Options (a), (c) and (d) describe respiration — the release of stored energy by oxidising food, taking in oxygen and giving out CO2 and water.

• Hence option (b).

Why the other options are wrong

(a) Potential energy is released to form free energy
Releasing potential energy is respiration.
(c) Food is oxidized to release carbon dioxide and water
Oxidising food is respiration.
(d) Oxygen is taken, and carbon dioxide and water vapour are given out
Taking oxygen and giving CO2 is respiration.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2014, held on 24 August 2014. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.

Reading the answer is not the same as getting it right under a clock. Practise this question with UPSC's negative marking, and anything you miss goes into an error notebook until you get it right twice.

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