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Question
The substrate for photorespiration is
The substrate for photorespiration is
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Solution
The correct option is A Glycolate.
The process, photorespiration, is a costly side reaction of photosynthesis, a result of the lack of specificity of the enzyme rubisco. RuBisCO is not absolutely specific for CO2 as a substrate. Molecular oxygen competes with CO2 at the active site, and about once in every three or four turnovers, RuBisCO catalyzes the condensation of O2 with ribulose 1,5-bisphosphate to form 3-phosphoglycerate and 2-phosphoglycolate, a metabolically useless product. The reaction with O2 results in no fixation of carbon and appears to be a net liability to the cell; salvaging the carbons from 2-phosphoglycolate consumes significant amounts of cellular energy and releases some previously fixed CO2.
The process, photorespiration, is a costly side reaction of photosynthesis, a result of the lack of specificity of the enzyme rubisco. RuBisCO is not absolutely specific for CO2 as a substrate. Molecular oxygen competes with CO2 at the active site, and about once in every three or four turnovers, RuBisCO catalyzes the condensation of O2 with ribulose 1,5-bisphosphate to form 3-phosphoglycerate and 2-phosphoglycolate, a metabolically useless product. The reaction with O2 results in no fixation of carbon and appears to be a net liability to the cell; salvaging the carbons from 2-phosphoglycolate consumes significant amounts of cellular energy and releases some previously fixed CO2.
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