The oxygenation activity of RuBisco enzyme is photorespiration leads to the formations of:
Answer: (D) 1 molecule of 3-C compound. In photorespiration the oxygenase activity of RuBisCO makes RuBP bind O2 instead of CO2, yielding one molecule of phosphoglycerate (3-carbon) and one molecule of phosphoglycolate (2-carbon).
- A.1 molecule of 6-C compound
- B.1 molecule of 4-C compound and 1 molecule of 2-C compound
- C.2 molecules of 3-C compound
- D.1 molecule of 3-C compound✓
Correct Answer
(D) 1 molecule of 3-C compound
Solution & Explanation
In photorespiration the oxygenase activity of RuBisCO makes RuBP bind O2 instead of CO2, yielding one molecule of phosphoglycerate (3-carbon) and one molecule of phosphoglycolate (2-carbon). The biochemically complete answer is '1 molecule of 3-C and 1 molecule of 2-C', which is not offered cleanly (option B wrongly states 4-C). The official external key marks option D, the 3-carbon phosphoglycerate that re-enters the Calvin cycle; the options are weak/defective and this item should be flagged for human spot-check. (Answer is from an external key, as the 2020 PDF had no biology key.) NCERT: Class 11 Ch 11, p.147 [147:037-040]: "Here the RuBP instead of being converted to 2 molecules of PGA binds with O2 to form one molecule of phosphoglycerate and phosphoglycolate (2 Carbon) in a pathway called photorespiration." (Answer per official NEET key; 2020 paper had no printed biology key.)