1. Exceptions to Normal Photosynthesis
Unit 3 Part 3

2. Cross Section of a Leaf

3. Photorespiration = super bad for plants!!
Both O2 and CO2 fit the active site of Rubisco (O2 is a competitive inhibitor!!!)
Remember, Rubisco is supposed to fix CO2 to RuBP
When O2 bonds to Rubisco, it is called photorespiration
If O2 goes into the active site of Rubisco, no CO2 can be used to build glucose
NO glucose = NO growth

5. How different plants deal with photorespiration
C3 plants (most plants): These plants leave their stomata open all the time, but to deal with photorespiration they just have massive amounts of the enzyme Rubisco. That way, even if half of the Rubisco are made useless by photorespiration, there are still enough Rubisco to make sufficient levels of glucose.
C4 plants (corns, tropical grasses): These plants separate where carbon fixation and the rest of the Calvin Cycle happen. CO2 is fixed in a mesophyll cell in the leaf, and the rest of the Calvin Cycle happens in a bundle sheath cell (away from O2).
CAM plants (succulents, desert plants): These plants separate when carbon fixation and the rest of the Calvin Cycle happen. Since stomata must stay shut during the day (to not lose water) lots of oxygen builds up, so photorespiration is very likely. The Calvin Cycle only happens during the night in these plants when the stomata are open and O2 can leave the cell.

7. Exceptions to Normal Photosynthesis