NEETBotanyPhotosynthesis in Higher Plants
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): In C₃ plants, some O ₂ binds to RuBisCO, resulting in a decrease in CO ₂ fixation. Reason (R): RuBisCO has a much greater affinity for O ₂ than for CO ₂ . In the light of the above statements, choose the correct answer from the options given below:
Options
- ABoth (A) and (R) are true and (R) is the correct explanation of (A)
- B(A) is true but (R) is false
- CBoth (A) and (R) are true but (R) is not the correct explanation of (A)
- D(A) is false but (R) is true
Correct answer
B. (A) is true but (R) is false
Step-by-step solution
Assertion (A) is true: In C₃ plants, RuBisCO can bind to O ₂ instead of CO ₂ due to its dual catalytic nature. When O ₂ binds to RuBisCO, the wasteful process of photorespiration is initiated, which utilizes ATP and releases CO ₂ without synthesizing sugars, thereby decreasing the overall CO ₂ fixation. Reason (R) is false: According to NCERT, RuBisCO has a much greater affinity for CO ₂ than for O ₂ . The binding of these gases is competitive, and it is the relative concentration of O ₂ and CO ₂ at the active site