1. Bio I Rupp

2. Focusing Questions Where does the energy to do work come from? What chemical do cells use for energy? What is the equation for photosynthesis? How are chloroplasts arranged? What is NADPH? What are the two reaction pathways in photosynthesis?

3. Energy Light or solar energy is converted to chemical energy This occurs in the chloroplast of plants Plants Blue-green algae Photosynthetic bacteria

4. History of Photosynthesis Jan van Helmont Belgian Physician 1643 Willow tree experiment What caused the tree to gain weight?

5. History of Photosynthesis con’t. Joseph Priestley English minister and chemist 1771 Candle experiment What did the plant produce?

7. History of Photosynthesis con’t. Jan Ingenhousz Dutch scientist 1779 Repeat of Priestley’s work Plants only functioned in what?

9. History of Photosynthesis con’t. Based on the experiments of van Helmont, Priestley, and Ingenhousz, what three things can we say plants need/produce?

10. Photosynthesis Equation CO 2 + H 2 O + Light C 6 H 12 O 6 + O 2

11. Leaf Structure Epidermis—outer cells of leaf Palisade mesophyll—where the majority of chloroplasts are located Spongy mesophyll—some chloroplasts are located here

13. Leaf Structure con’t. Xylem—water transport Phloem—food transport Cuticle—waxy covering that stops evaporation of water from the leaves Stoma—opening in leaf that allows CO 2 to enter

15. Chloroplast structure Stroma—the fluid interior that surrounds the other chloroplast structures Granum—stacks of disk shaped thylakoids Thylakoids—the site of photosynthesis

17. Chloroplast structure con’t. What makes the chloroplasts green? Pigments Chlorophyll a (650-700nm and 400-450nm) Chlorophyll b (450-500nm and 650nm) Carotenoids (450 nm) Xanthophyll (600nm)

19. How does Photosynthesis Work? Light is captured Light energy is converted to chemical energy The chemical energy is a combination of ATP NADPH Sugars Light reaction pathways Dark reaction pathways

20. Light Reactions Step one Light hits photosystem II and boosts electrons to higher energy level H + ions are transported to create a concentration gradient ATP is produced

21. Light Reactions con’t.

22. Step Two Low energy electrons enter photosystem I and is re- energized The re-energized electrons then move into the NADPH electron chain

23. Light Reactions con’t.

24. Restoring Photosystem II If electrons keep moving out where are the initial electrons coming from? Water splitting reaction

25. H+ ions and ATP Creation How did H+ ions move across the thylakoid membrane? They were pumped by ATP synthase Facilitated diffusion

26. Dark Reactions Also known as the Calvin Cycle or Light Independent reactions The ATP and NADPH from the light reactions is used to turn CO 2 into sugar

27. Dark Reactions con’t. Step one Carbon fixation CO 2 is attached to a 5 carbon sugar called ribulose bisphosphate (RuBP) The resultant molecule is unstable and splits into two 3-carbon molecules of PGA

28. Dark Reactions con’t. Step two Reduction ATP and NADPH are used to rearrange the two 3-carbon molecules of PGA

29. Dark Reactions con’t. Step three Regeneration of RuBP Two of the PGAL molecules are used to make glucose The remaining PGAL is rearranged, with the help of ATP, to RuBP

30. Photosynthesis Overview

31. Alternative pathways C3 plants Fix carbon to RuBP via the enzyme rubisco Rubisco is probably the most abundant enzyme on Earth If CO 2 levels drop then the Calvin Cycle is starved Photorespiration

32. Alternative Pathways con’t. C4 plants CO 2 is fixed into a 4- carbon compound The mesophyll cells store the CO 2 to keep feeding the Calvin Cycle Slows down photorespiration Good method for plants in hot climates

33. Alternative Pathways con’t. CAM plants Crassulacean acid metabolism CO 2 is gathered at night and stored CO 2 can be released to keep the Calvin Cycle running Photorespiration decreases

35. Factors Affecting Photosynthesis Light intensity CO 2 levels Temperature