1. Stage 2 - Conversion of light Energy Stage 3 - Storage of Energy
Photosynthesis
Stage 2 - Conversion of light Energy
Stage 3 - Storage of Energy

2. Stage 2 - Conversion of Light Energy
Light energy is converted to chemical energy
Excited electrons that leave the chlorophyll pigments in Stage 1 are used
Excited electrons are passed through proteins in the thylakoid membrane like a ball being passed from person to person

3. Electron Transport Chains
1st ETC occurs between to pigment molecules
Uses a protein that acts as a membrane pump
Electrons lose energy as they pass through this protein

4. Energy lost by these electrons is used in the protein to pump hydrogen ions (H+) into the thylakoid (active transport)
This pump along with splitting water molecules provides a concentration gradient inside the thylakoid

5. Due to the high concentration gradient of H+ inside the thylakoid, some H+ diffuse out of the thylakoid
This passive transport occurs through specialized carrier proteins

6. These carrier proteins also work as an enzyme
They also catalyze a reaction where a Phosphate is added to a molecule of ADP
ADP + P --> ATP (energy is produced)

7. The ATP produced is used in the 3rd stage of photosynthesis

8. 2nd ETC occurs with pigment molecule
Produces NADPH to help power 3rd stage of photosynthesis

9. Excited electrons combine with an electron acceptor NADP+
NADP+ + H+ --> NADPH (energy carrier)

10. Summary of Light Dependent Reactions
Pigment molecules in thylakoid absorb light energy
Electrons excited by light move through ETC in thylakoid
These electrons are replaced by water molecules

11. Oxygen atoms from water combine to form oxygen gas
H+ concentration inside thylakoid increases

12. Concentration gradient provides energy to make ATP
H+ combine with NADP to create NADPH, an energy carrier molecule

13. Stage 3 - Storage of Energy
Organic compounds are formed (glucose)
Light independent reactions (dark rxns)
Transfer of carbon from CO2 to organic compounds (carbon dioxide fixation)

14. Calvin Cycle Most common method of carbon dioxide fixation
Occurs in 4 steps
Needs ATP and NADPH from Stage 2

15. Step 1 - CO2 is added to a 5 carbon compound
Step 2 - Resulting 6C compound splits into two 3C compounds. Phosphates from ATP and electrons from NADPH are added to form 3C sugars

16. These compounds are stored for later use by the organism
Step 3 - One 3C sugar is used to make organic compounds (starch and sucrose)
These compounds are stored for later use by the organism
3D model of sucrose

17. Step 4 - the five other 3C sugars create the 5C sugars that start the cycle again

18. The Calvin Cycle is named for Melvin Calvin
Discovered in 1950s at UC Berkley
3 CO2 molecules must enter the Calvin Cycle to produce each 3C sugar
The 3C sugars are used to make other organic molecules which provide energy for growth and metabolism

19. Factors that Affect Photosynthesis
Light - increased light intensity increases until all pigments are being used
Carbon dioxide - at a certain concentration photosynthesis can’t proceed any faster
Temperature - unfavorable temp. can inactivate certain enzymes

20. Alternate Carbon Dioxide Fixation
C4 PLANTS - Allows certain plants to fix CO2 into 4C compounds. During the Hottest part of the day, C4 plants have their stomata partially closed. Include corn, sugar cane and crabgrass. Conserves water in the plant

21. CAM PLANTS - Cactus, pineapples must survive in hot, dry climates
CAM PLANTS - Cactus, pineapples must survive in hot, dry climates. Plants open their Stomata at night and close during the day. They grow slowly, but lose less water.