Photosynthesis in Higher Plants PYQ's (MCQ's)

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Previous Year Questions:

1. Which of the following are required for the dark reaction of photosynthesis ?                    (2024)

     A) Light      B) Chlorophyll      C) CO2      D) ATP      E) NADPH

Choose the correct answer from the options given below:

1) A,B and C only      2) B,C and D only

3) C,D and E only      4) D and E only

Ans. 3 - C,D and E only

Explanation: Dark reaction of photosynthesis is also known as Calvin cycle. For every CO2 molecule entering the Calvin cycle, 3 molecules of ATP and 2 of NADPH are required. Hence CO2, ATP and NADPH are required for dark reaction of photosynthesis.

2. How many molecules of ATP and NADPH are required for every molecule of CO2 fixed in the Calvin cycle ? (2024)

1) 2 molecules of ATP and 3 molecules of NADPH
2) 2 molecules of ATP and 2 molecules of NADPH
3) 3 molecules of ATP and 3 molecules of NADPH
4) 3 molecules of ATP and 2 molecules of NADPH

Ans. 4 - 3 molecules of ATP and 2 molecules of NADPH

Explanation: For every CO2 molecules entering the Calvin cycle, 3 molecules of ATP and 2 molecules of NADPH are required.

3. Given below are two statements:

Statement I: In C3 plants, some O2 binds to RuBisCO, hence CO2 fixation is decreased.
Statement II: In C4 plants, mesophyll cells show very little photorespiration while bundle sheath cells do not show photorespiration.

In the light of the above statements, choose the correct answer from the options given below: (2024)

1) Both statement I and statement II are true 
2) Both statement I and statement II are false
3) Statement I is true but statement II is false
4) Statement I is false but statement II is true

Ans. 3 - Statement I is true but Statement II is flase

Explanation: In C3 plants, some O2 binds to RuBisCO, hence CO2 fixation is decreased. Statement II is false because mesophyll cells lack RuBisCO and hence photorespiration does not occur in mesophyll cells.

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