3-3 plant exchange systems

3-3 plant exchange - P LANT EXCHANGE SYSTE MS L IFE 8.4 8.4 How do plants adapt to the inefficiencies of photosynthesis-One major limi tation of

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PLANT EXCHANGE SYSTEMS LIFE 8.4 8.4 How do plants adapt to the inefficiencies of photosynthesis? -One major limitation of rubisco is its tendency to react with O 2 instead of CO 2 photorespiration (lowers the overall rate of CO 2 fixation) 8.4.1 Rubisco catalyzes RuBP reaction with O 2 as well as CO 2 - rubisco is an oxygenase as well as a carboxylase (can add O 2 to the acceptor molecule RuBP instead of CO 2 ). These two reactions compete with each other, so if RuBP reacts with O 2 , it cannot react with CO 2 reduces the overall amount of CO 2 that is converted into carbohydrates limits plant growth -When O 2 is added to RuBP, one of the products is a 2-carbon compound , phosphoglycolate: RuBP + O 2 phosphoglycolate + 3PG Plants have evolved a metabolic pathway that can partially recover the carbon that has been channeled away from the Calvin cycle into phosphoglycolate: phosphoglycolate forms glycolate diffuses into peroxisomes converted to amino acid glycine: glycolate glycine glycine diffuses into a mitochondrion two glycine
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This note was uploaded on 09/02/2009 for the course BIO 315H taught by Professor Payne during the Spring '08 term at University of Texas at Austin.

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3-3 plant exchange - P LANT EXCHANGE SYSTE MS L IFE 8.4 8.4 How do plants adapt to the inefficiencies of photosynthesis-One major limi tation of

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