Biology 311C Lecture 26 part 1

Biology 311C Lecture 26 part 1 - October 26, 2011 Biology...

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October 26, 2011 Biology 311C Lecture 26 Photorespiration occurs when higher than normal levels of oxygen are present in the leaf. When you close the stomata, the oxygen levels go up and it occurs photorespiration. C 4 is named for the 4-carbon molecule present in the first product of carbon fixation in these plants. Both C 4 and CAM store carbon dioxide. C 4 stores it as a 4 carbon organic acid. CAM photosynthesis is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. The stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide (CO2). The CO2 is stored as the four-carbon acid malate, and then used during photosynthesis during the day. The pre-collected CO2 is concentrated around the enzyme RuBisCo, increasing photosynthetic efficiency. PEP carboxylase is better than RuBisCo because it has a high affinity for carbon dioxide.
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