PHOTOSYNTHESIS II

PHOTOSYNTHESIS

Two Raw Materials
          - Carbon Dioxide - stomata
          - Water - xylem vessels

                     CO2 + H2O + light ------------> C6H12O6 + H2O 

Two Processes

• Light Dependent or Photolysis
• Light Independent or Dark Reaction

LIGHT DEPENDENT
          - also called photolysis
          - occurs in the thylakoids
          - involves: Photosystem I
                          Photosystem II

Photosystem I
          - reaction center is 700
          - far-red region
          - more in chlorophyll a

Photosystem II
          - reaction center is 680
          - red region
          - in chlorophyll a and chlorophyll b

LIGHT ENERGY --------> chlorophyll a
                                (electrons excited)(P680)
                                                   |
                                                   |
                                      energized chlorophyll
                                                   / \
                                                  /   \
                                  splits water    adds P1
                                         / \                |
                                        /   \               |
                                     2H  O2     ADP(energy carrier)
                                       |                    |
                                       |                    |
                       NADP(H acceptor)    ATP
                                       |                    |
                                       |                    |
                                 NADPH          energy   
                                         \                   /
                                           \               /
                                    DARK REACTIONS

LIGHT INDEPENDENT
          - dark reactions
          - Calvin-Benson reaction
          - carbon fixation
          - occurs in the stroma

                                                      CO2
                                                          |
                                                          |
                                                   RuDP(CO2 acceptor)
                                                          |
                                                          |
                                           6-C sugar (very unstable)
                                                          | splits
                                                          |
                                 2 mols. of PGA (3 carbon compound) 
                                                          | combine
                                                          |    with
                                 2H from NADPH (from Light Reaction)
                                                        / \
                                                       /   \
                                                      /     \
                                             PGAL    H20 released as by products
                                                / \
                                               /   \
                                      RuDP    Glucose

External Factors that Affect Photosynthesis

1. light
2. Carbon Dioxide
3. temperature
4. water supply
5. minerals

Internal Factors

1. leaf structures
2. amount of photosynthetic products
3. enzymes