1. Photosynthesis

2. Light Reactions: Trapping Energy
Takes place in the stacks of thylakoids (grana) inside the chloroplast
Thylakoid
Grana

4. Steps in the Light Reaction
Light strikes the electrons in chlorophyll
Electrons:
Absorb energy
Leave the chlorophyll molecule
Are caught and passed down the Electron Transport Chain
Lose energy
Energy is stored as ATP.

5. Steps in the Light Reaction
At the same time:
4. Chlorophyll picks up an e- from water
5. Causes water to split  2H + and O
(photolysis)
6. Freed H + ions are picked up by NADP+  NADPH + H+
(coenzyme)
7. Oxygen is given off as a waste product

6. Other Points Light reactions are really three separate reactions.
Energy absorption
ETC
Splitting of water
ATP and NADPH are not stable enough for long term energy storage.

7. Summary (put in margin)
Starts with:
Light and water
Produces:
NADPH
ATP O2
Takes place in the:
Thylakoids /grana

8. Calvin Cycle: Making Sugar
Takes place in the stroma which surrounds the grana
Uses the stored energy of the light reaction

9. Steps in the Calvin Cycle
C (from CO2) is added to a reusable 5C molecule by the enzyme, rubisco.
(carbon fixation)
2. Unstable 6C molecule breaks down into two 3C molecules (PGA)
3. Hydrogen from NADPH and energy from ATP is used to make stable molecules
3C molecules + NADPH + ATP  stable 3C + NADP+ + ADP + P

10. Steps in the Calvin Cycle
4. Repeated 6 times.
5. Eventually two 3C molecules are removed from cycle and used to make glucose.
(can also make other sugars)
6. Remaining 3C molecules are converted back into the 5C molecule that originally picked up the C

11. Summary (put in margin)
Starts with:
CO2 (air)
NADPH
ATP
Reusable 5 C molecule
Produces:
Glucose
ADP + P
NADP+
Takes place in the:
stroma

12. Factors that affect rate of photosynthesis
Amount of water
Light intensity
Temperature
Presence of minerals

13. H2O
CO2
Light
NADP
ADP
Calvin Cycle
(stroma)
Light Reactions
grana
ATP
NADPH
Other products O2
Glucose