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In c4 and cam plants carbon dioxide is fixed in the _____ of mesophyll cells. in c4 and cam plants carbon dioxide is fixed in the _____ of mesophyll cells. cytoplasm stroma stomata grana thylakoids

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In C4 and CAM plants carbon dioxide is fixed in the cytosol of mesophyll cells.  

C4 and CAM plants have specially adapted metabolic pathway in order to limit exposure of Rubisco enzyme to oxygen (oxygen can inhibit Rubisco and reduce photosynthesis that way). C4 plants separate steps of CO2 fixation and Calvin cycle in two different cell types. CAM plants separate these steps in time, between night and day.
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Answer:

cytoplasm.

Explanation:

The leaves of plants known as C4 have two different types of cells containing chloroplasts: the mesophyll and the vascular bundle sheath, which are connected by an extensive network of plasmododes. The cells of the bundle sheath present a differentiated, crown-shaped anatomy known as the kranz anatomy. During photosynthesis, in the first stage, CO2 (as HCO3-) is fixed by the enzyme phosphoenolpyruvate carboxylase (PEP-carboxylase) in the cytosol of mesophyll cells, forming oxaloacetate. This organic acid is converted to malate or aspartate, depending on the species, in the chloroplasts of the mesophyll cells.

In CAM plants, CO2, in the form of HCO3 -, is captured by the PEP carboxylase in the cytosol of mesophyll cells, which combines HCO3- with phosphoenolpyruvate, producing oxaloacetate. What differentiates these plants from the others is that this CO2 fixation process occurs during the night. The oxaloacetate formed is then converted to malate, which accumulates in vacuoles. This accumulation of organic acids during the night explains the name CAM - acid metabolism of crassulaceae, common in cacti, bromeliads, orchids, euphorbiae and crassulaceae. During the day, the stored malate is transported to the chloroplasts and decarboxylated, releasing CO2 that is reduced by the Calvin cycle.