Tuesday, October 22-Notes-C4 photosynthesis

IX. C4 Photosynthesis-Solves the photo-respiration problem. 2 types of plants that run a C4 photosynthesis:
     A. C4 Plants- sugarcane, corn

         1. CO2 enters a Mesophyll cell where it is fixed onto a PEP molecule by PEP carboxylase forming a 4-C molecule (malate).
             PEP (3-C)  + CO2 (1-C) ==> malate (4-C) (this is where the C4 cycle gets its name-there are 4 carbons)
         2. The Malaate diffuses into a Bundle-Sheath cell where it gives off a CO2 to the Calvin Cycle (same as C3 photosynthesis) The 3-C molecule "left over" is pyruvate. So, all of the sugars are made in Bundle-Sheath Cells.
         3. The pyruvate diffuses back into the Mesophyll cell, is converted back to PEP (uses an ATP) and the cycle starts over.
     B.CAM Plants-Cacti, Pineapple
 

      
         1. CO2 is fixed during the night when stomata are open into the C4 pathway.
         2. C4 molecule gives up its CO2 during the day to the Calvin Cycle.