Photosynthesis - General

The following points describe the significance and relationship of photosynthesis to life on earth.

  1. Photosynthesis begins the carbon cycle by fixing CO2 (carbon dioxide in the atmosphere)


  1. It has 2 major metabolic components: the light reactions and the "dark" reactions


  1. The overall equation for photosynthesis is:


6 CO2 + 12 H2O + energy C6H12O6 + 6 H2O + 6 O2



  1. This equation leaves out many important details such as:


  1. where does the O2 gas come from? (water)
  2. how is light energy converted into chemical bond energy? (see light reaction and "reaction" sections)


  1. The oxygen released as a by-product has a major impact on the bioshpere. Today's atmosphere would not have 21% oxygen if not for photosynthesis.


  1. Three kingdoms have photosynthetic autotrophs (producers)


  1. monera - cyanobacteria
  2. protista - algae
  3. plants


  1. Photosynthesis is endergonic G = +686 kcal/mole