1. Limiting Factors in Photosynthesis Song Hee Bae IB1 Biology

2. The Concept of Limiting Factors • Light intensity • Carbon dioxide concentration • Temperature • Changing the limiting factor increases or decreases the rate

3. The Effect of Light Intensity • Not usually the limiting factor • At low light intensities, shortage of NADPH and ATP • Rate-limiting where Glycerate 3-phosphate is reduced

4. The Effect of CO₂ Concentration • At low and medium CO₂ • Rate-limiting where CO₂ is fixed to produce glycerate 3-phosphate • Level of CO₂ is never very high • Often the limiting factor

5. The Effect of Temperature • At low temperature, enzymes work slowly • At high temperature, RuBP ineffective • Rate-limiting where CO₂ is fixed

6. Temperature CO₂ Concentration Light intensity

7. Results of Limiting Factors

8. Cyclic Photophosphorylation • When light is not limiting factor • NADPH accumulation, NADP+ shortage • Normal flow of electrons inhibited • Alternative route is cyclic photophosphorylation • See page 81

9. Vocabulary • Limiting factor • Cyclic photophosphorylation Reference • Study guide page 81