D. Modes of Photosynthesis 1. In C3, plants Calvin cycle fixes CO2 directly; first molecule following CO2 fixation is PGA, a C3 molecule. 2. C4 leaves fix CO2 by forming a C4 molecule prior to the involvement of the Calvin cycle. 3. CAM plants fix CO2 by forming C4 molecule at night when stomates can open without loss of water. 4. C4 Photosynthesis a. In a C4 plant, mesophyll cells contain well-formed chloroplasts arranged in parallel layers. b. In …showed first 75 words of 444 total…

…showed last 75 words of 444 total…the Calvin cycle within the same cell, which now has NADPH and ATP available to it from the light-dependent reactions. d. CAM plants open stomates only at night, allowing CO2 to enter photosynthesizing tissues; during the day, stomates are closed to conserve water and CO2 cannot enter photosynthesizing tissues. e. Photosynthesis in a CAM plant is minimal, due to limited amount of CO2 fixed at night; does allow CAM plants to live under stressful conditions.