1. Concept 2: Analyzing the Processes of Photosynthesis PART 2 – Adaptations to Dry Climates
Refer to pg in Holtzclaw, Ch 10 in Campbell and media resources
Refer to pg in Holtzclaw, Lab 4 in LabBench

3. Try This!
Where does the organic biomass of a tree primarily come from?
Oxygen
Water
Carbon dioxide
Light
Fertilizer
Carbon dioxide!

4. A building block for organic molecules!
Try This!
Where does the organic biomass of a tree primarily come from?
Oxygen
Water
Carbon dioxide
Light
Fertilizer
CO2
Carbon dioxide!
A building block for organic molecules!

5. Chapter 10
You must know:
How photosystems convert solar energy to chemical energy
How linear electron flow in the light reactions results in the formation of ATP, NADPH, and O2
How chemiosmosis generates ATP in the light reactions
How the Calvin cycle uses the energy molecules of the light reactions to produce G3P
The metabolic adaptations of C4 and CAM plants to arid, dry regions

6. AP Lab 4
You must know:
The equation for photosynthesis and understand the process of photosynthesis
The principles of chromatography and how to calculate Rf values
The relationship between light wavelength or intensity and photosynthetic rate
How to determine the rate of photosynthesis and then be able to design a controlled experiment to test the effect of some variable factor on photosynthesis

9. Photosynthesis – The Basics
CO2 + H2O → C6H12O6 + O2
Light Reactions “photo”
Calvin Cycle “synthesis”

14. The Light Reactions

15. The Light Reactions Light energy excites electrons in chlorophyll
Removal of electrons from H2O
Formation of O2
Electron Transport Chain
Reduction of NADP+ to NADPH
Proton Motive Force
ATP Synthase to produce ATP

16. H+! Proton Motive Force

18. Try This
Unlike in cellular respiration, the proton motive force generated by the light reactions in photosynthesis happens in three ways… Can you remember the three ways?
Electron transport chain powering the active transport of H+ into the thylakoid space
H+ produced in the thylakoid space from the splitting and oxidation of water
Removal of H+ from stroma during the reduction of NADP + to NADPH

19. The Light Reactions
The whole point was to transfer light energy to chemical energy in the form of:
electrons in NADPH
ATP
Why?
To power carbon fixation in the Calvin Cycle…

21. Carbon Fixation! The Calvin Cycle
CO2 enters as a gas through the stomata (openings) of the leaves
Through the power of NADPH and ATP, CO2 gets converted into an organic compound: a 3-carbon sugar called glyceraldehyde-3-phosphate (G3P)
Can be converted to glucose, sucrose, starch, etc…

24. The whole point…

25. How does this affect YOU?

27. Chapter 10
You must know:
How photosystems convert solar energy to chemical energy
How linear electron flow in the light reactions results in the formation of ATP, NADPH, and O2
How chemiosmosis generates ATP in the light reactions
How the Calvin cycle uses the energy molecules of the light reactions to produce G3P
The metabolic adaptations of C4 and CAM plants to arid, dry regions

28. NOW… Adaptations to hot, arid climates… CAM plants and C4 plants
Sugarcane – C4 plant
Pineapple – CAM plant

29. Hot, Dry Climates What’s the big deal? Stomata – water loss
Rubisco – photorespiration

30. Stomata…

31. Stomata…
Water exits via stomata during transpiration (evaporation of water through the stomata - which pulls water up the plant from the roots)
If it’s a hot, dry day, plants need to minimize water loss!
Solution?
Close/minimize stomata
BUT? Lowers CO2 intake…

32. Rubisco… Remember rubisco?
It’s the enzyme that fixes CO2 in the Calvin cycle of C3 plants
The thing is… rubisco will also bind O2 in absence of CO2
Causes breakdown of Calvin Cycle products… Photorespiration
Solution?
Adapt!

36. Try This!
The presence of only Photosystem I, not Photosystem II, in the bundle sheath cells of C4 plants has an effect on O2 concentration. What is that effect, and how might that benefit the plant?

37. Try This!
The presence of only Photosystem I, not Photosystem II, in the bundle sheath cells of C4 plants has an effect on O2 concentration. What is that effect, and how might that benefit the plant?
Without PS II, no O2 is generated in the bundle-sheath cells!
This avoids the problem of O2 competing with CO2 for binding to rubisco
No photorespiration

38. Now… Practice Re-Read about CAM plants and C4 plants and do worksheet
Try #12 – 15, 17-19, p
Go over Comparison Charts
Try animation activities (Campbell Online)
Re-Read about CAM plants and C4 plants and do worksheet
P Holtzclaw
P Campbell
Activity: Photosynthesis in Dry Climates (Campbell Online)
Get Ready for Lab 4
Go through Lab 4 LabBench
Checkpoint Next Class on Photosynthesis (Concept 2)