RuBP and RuBisCO in Calvin Cycle — NEET Biology
📚 Practice ConceptLet us try and understand one more process that creates an important difference between C₃ and C₄ plants – Photorespiration. To understand photorespiration we have to know a little bit more about the first step of the Calvin pathway – the first CO₂ fixation step. This is the reaction where RuBP combines with CO₂ to form 2 molecules of 3PGA, that is catalysed by RuBisCO.
Which of the following statements about photorespiration and associated enzymes are NOT correct? S1: RuBisCO is unique in that its active site has a much greater affinity for O₂ than for CO₂, leading to inefficient carbon fixation in C₃ plants. S2: In the photorespiratory pathway, RuBP binds with O₂ to form one molecule of phosphoglycerate and phosphoglycolate, which results in the release of CO₂ and utilization of ATP. S3: The wasteful oxygenation activity of RuBisCO is completely avoided in C₄ plants due to the absence of RuBisCO enzyme in their mesophyll cells. S4: The biological function of photorespiration is currently understood to be an adaptive mechanism that provides an important advantage to C₃ plants in dry and hot conditions. S5: Cyclic photophosphorylation occurs to generate additional ATP required to meet the higher ATP to NADPH ratio needed for the Calvin cycle (3 ATP: 2 NADPH per CO₂ fixed). Choose the option with the NOT correct statements:
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