Photosynthesis Question 51
51. The oxygenation activity of RuBisCo enzyme in photorespiration leads to the formation of
[2020]
(a) 1 molecule of 3-C compound
(b) 1 molecule of 6-C compound
(c) 1 molecule of 4-C compound and 1 molecule of 2-C compound
(d) 2 molecules of 3-C compound
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Answer : a
Hints & Solution
(a) In photorespiration, $O_2$ binds to RubisCo. As a result $RuBP$ instead to being converted to 2 molecules of PGA bind with $O_2$ to form one molecule each of phosphoglycerate (3 carbon compound) and phosphoglycolate ( 2 carbon compound). Photorespiration is the oxygenation of RuBP by RUBISCO followed by photorespiratory glycolate metabolism. Competition between $O_2$ and $CO_2$ reduces the rate of carbon assimilation, energetic efficiency of photosynthesis, and may reduce the photosynthetic quotient $(PQ=O_2.$ evolved $/ CO_2$ assimilated).
