1. 1 Review Summarize what happens during the light dependant reactions 2 Explain How do each of the three primary factors affect the rate of photosynthesis 3 Review What are the different ways that plants cope with water shortages

2. 8.3 The Process of Photosynthesis
Ch 8 Photosynthesis
8.3 The Process of Photosynthesis

3. Why do chloroplasts contain so many membranes?
Membranes are the key to capturing light energy.

4. Light Dependant Reactions: Generating ATP and NADPH
Photosystems
Series of proteins in the thylakoid that absorb sunlight and make high-energy electrons.

5. Electron Transport Chain
Series of electron carriers that shuttle high-energy electrons during ATP-generating reactions
Electron Transport Chain (ETC).

6. Photosystem II Light energy is absorbed by electrons
High energy electrons move through the ETC.

7. Photosystem II Thylakoid provides new electrons from water
Water breaks up into 2 electrons, 2 H+ ions, and 1 oxygen atom.

8. Photosystem II
2 electrons replace the high-energy electrons that have been lost to ETC
H+ ions released inside thylakoid
Oxygen is released into the air.

9. Photosystem II
Energy from electrons is used by proteins in ETC to pump H+ ions from the stroma into the thylakoid space.

10. Photosystem II
The ETC gives electrons to Photosystem I.

11. Photosystem I
Electrons used energy to pump H+ ions so have less energy
Photosystem I uses energy from light to reenergize the electrons.

12. Photosystem I
After 2nd ETC, NADP+ molecules in the stroma pick up high-energy electrons and H+ ions at the outer surface of the thylakoid membrane to become NADPH.

13. Hydrogen Ion Movement and ATP Formation
H+ ions accumulate within the thylakoid space from splitting water and pumping them across.

14. Hydrogen Ion Movement and ATP Formation
Gradient of H+ ions
Charge and concentrations.

15. Hydrogen Ion Movement and ATP Formation
H+ ions cannot directly cross membane
ATP synthase
Protein that allows H+ ions to pass through
Causes it to rotate and bind ADP and a phosphate.

16. Hydrogen Ion Movement and ATP Formation
Produces NADPH and ATP.

17. The Light-Independent Reactions: Producing Sugars
Called the Calvin Cycle
Plants use ATP and NADPH to build stable high- energy carbohydrate compounds that can be stored for a long time.

18. Carbon Dioxide Enters the Cycle
Carbon dioxide molecules enter the Calvin cycle from the atmosphere
Combine CO2 with 5-carbon compounds
6 CO2 enter, twelve 3-carbon compounds are produced.

19. Enzymes convert the 3- carbon compounds into higher-energy forms using ATP and NADPH.

20. Sugar Production
Two of the 3-carbon molecules are removed to make sugar.

21. Sugar Production
Remaining ten 3- carbon molecules are converted back into six 5-carbon molecules
Combine with the new CO2 to start the next cycle.
ADP
ATP

22. Summary of the Calvin Cycle
Uses 6 molecules of carbon dioxide to produce a single 6- carbon sugar.
ADP
ATP

23. Energy for the reactions is supplied by compounds produced in the light-dependent reactions.
ADP
ATP

24. Sugars are used by the plant for energy needs and to build other macromolecules for growth and development.
ADP
ATP

25. Factors Affecting Photosynthesis
Temperature
Light intensity
Water availability.

26. Temperature Enzymes work best between 0°C and 35°C
Lower temps slow enzymes
Higher temps denature enzymes.

27. Light Intensity
High light intensity increases the rate of photosynthesis
There is a maximum to light intensity increasing photosynthesis.

28. Water Availability Water is needed in the reaction
Water shortage can stop reaction
Certain plants have special adaptations
C4 plants
CAM plants.

29. C4 Photosynthesis Very good and getting CO2 Uses a 4 carbon molecule
Requires added energy
Corn, sugar cane, and sorghum.

30. CAM Plants Open their leaves at night and trap CO2
Seal leaves shut during day to conserve water and use trapped CO2
Pineapple trees and many desert cacti.