Energy Capturing Pathways (Photosynthesis)

1. Energy Capturing Pathways (Photosynthesis) I. Introduction A. History 1. van Helmont, 1630, proved plants need water 2. Priestly, 1772, proved plants need gas (phlogiston)

2. 3. Ingenhaus, 1779, proved plants need sunlight 4. DeSaussure, 1804, organized all the pieces 5. van Neil, 1930, showed hydrogen in the glucose comes from splitting water Figure 10.5

3. B. Reduction/Oxidation Reactions 1. Redox = giving and receiving of electrons or energy Figure 9.3 Page 188

4. C. NADP+ and Energy Transfer Figure 9.4

5. II. Photosynthesis A. Organisms 1. Autotrophs Figure 10.2

6. B. Structures 1. Chloroplasts Figure 10.4

7. C. Background Info. 1. Light Properties Figure 10.8 Figure 10.7

8. 2. Pigments a. Chlorophylls are primary b. Xanthophyll's are secondary and reflect greens. and reflect blue/red. Figure 10.11

9. c. Carotenoids are secondary and reflect oranges and protect chlorophylls. Figure 10.9

10. III. Light Dependent Reactions A. Electron Excitation 1. Magnesium absorbs light energy and electrons get excited Figure 10.12

11. B. Where 1. Chloroplasts  light dependent reactions via chlorophyll pigments in the thylakoid membrane of chloroplasts Figure 10.13

12. C. Steps 1. Non-cyclic electron flow Figure 10.14 Non-cyclic Steps a. Light excites electrons of magnesium (oxidizes) of chlorophyll of photo-system II and I. b. Electrons from II are passed through an ETC to make ATP, while electrons from I are passed through an ETC to reduce NADP+. c. Electrons from II are used to backfill I chlorophyll that lost electrons to NADP+. d. Water is split by II to fill electrons lost to I by stealing electrons from hydrogen and provide a hydrogen to form NADPH + H+.

13. 2. Cyclic electron flow Figure 10.16 Cyclic Steps a. Light excites electrons of magnesium (oxidizes) of chlorophyll of photo-system Ionly. b. Electrons from I are passed through an ETC to make ATP only. c. Electrons from I are used to backfill I magnesium of the original chlorophyll. d. Water is not split.

14. Figure 10.18

15. D. Outcomes 1. The ATP and NADPH + H+ chloroplast stroma used to energize CO2 (ATP) & add hydrogen (NADPH + H+) 2. The O2 to the stomata to be expelled or to mitochondria Do plants need to keep expelling O2 for their benefit? Or yours?

16. IV. Light Independent Rxns. A. Where 1. Chloroplasts  The eight step process (Calvin cycle, the light independent reactions, or the DARK reactions) in chloroplast’s stroma. Figure 10.4

17. B. Steps Figure 10.19 a. Rubisco attaches 3CO2 to RuBP b. Requires 6ATP and 6NADPH + H+ to make 6G3P c. Separate 1G3P and hold in reserve d. Rearrange other 5G3P back into RuBP requiring 3ATP e. Repeat as long as you have enough ???? 1Glucose requires 18ATP + 12NADPH + H+

18. C. Outcomes What to do with the glucose?

19. V. Alternative Strategies A. Photorespiration 1. Definition 2. Mechanism 3. Examples B. C3 Plants 1. Definition 2. Mechanism C3 plants go senescent 3. Examples rice, wheat, some grasses, and soybean

20. C. C4 Plants 1. Definition 2. Mechanism C4 plants turn CO2 into acid molecules then break up to give CO2 to Rubisco 3. Examples sugarcane, corn, and other grasses Figure 10.20

21. D. CAM Plants 1. Definition 2. Mechanism CAM plants completely separate light from dark reactions 3. Examples cactus, pineapples, and succulents

22. C4 versus CAM plants Figure 10.21

23. Figure 10.22