Assertion: Photorespiration interferes with the successful functioning of Calvin cycle.
Reason: Photorespiration oxidises ribulose1,5 biphosphate which is an acceptor of CO2 in Calvin cycle.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
A.
If both assertion and reason are true and reason is the correct explanation of assertion.
In the 1920s, the German biochemist Otto Warburg (1883-1970) discovered that plants consumed oxygen at a higher rate when they were illuminated. He also found that this increased rate of oxygen consumption inhibited photosynthesis. Stimulation of oxygen consumption by light is now referred to as photorespiration. Biochemical studies indicate that photorespiration consumes ATP and NADPH, the high-energy molecules made by the light reactions. Thus, photorespiration is a wasteful process because it prevents plants from using their ATP and NADPH to synthesize carbohydrates.
RuBISCO, the enzyme which fixes carbon dioxide during the Calvin cycle, is also responsible for oxygen fixation during photorespiration. In particular, carbon dioxide and oxygen compete for access to RuBISCO. RuBISCO's affinity for carbon dioxide is much higher than its affinity for oxygen. Thus, fixation of carbon dioxide typically exceeds fixation of oxygen, even though atmospheric carbon dioxide levels are about 0.035% whereas oxygen is about 21%.
