1. 8-1 Chapter 8: Photosynthesis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 8-2 Radiant Energy Photosynthesis converts solar energy into the chemical energy of a carbohydrate : Solar energy + 6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6O 2 Carbohydrate (glucose) OxidizedReduced Electrons from H 2 O are energized by the sun. The oxygen given off comes from water – 18 O experiments.

3. 8-3 Photosynthetic organisms These organisms are called producers; they synthesize organic molecules from raw materials. Plant Algae Cyanobacteria

4. 8-4 Nearly all life is dependent on solar energy because photosynthetic organisms: 1)use solar energy to produce organic nutrients. 2)provide food (producers) for other organisms (consumers). And, 3) The bodies of plants became the coal or other fossil fuels used today.

5. 8-5 Visible Light Fig 8.2 Pigments (chlorophylls and carotenoids) found within photosynthesizing cells, are capable of absorbing various portions of visible light. Both chlorophyll a and chlorophyll b absorb violet, blue, and red light best and green least.3

6. 8-6 Mesophyll cells of a leaf contain chloroplasts Water reaches mesophyll cells from vessels that extend to the roots. Pores called stomata allow CO 2 and O 2 to enter the leaf. Leaf Structure Fig 8.3

7. 8-7 Chloroplast structure Double membrane Chlorophyll and other pigments are found in the thylakoids Thylakoids are interconnected Fig 8.3

8. 8-8 Two Sets of Reactions for Photosynthesis Light Dependant Reactions ‘Photo-’ Cyclic and Noncyclic electron pathways -Captures energy from the sun Light Independent Reactions ‘-Synthesis’ Calvin Cycle -Produces carbohydrate

9. 8-9 The light-dependent reactions: the cyclic electron pathway Fig. 8.4 -Produces only ATP! Solar Energy

10. 8-10 The light-dependent reactions: the noncyclic electron pathway Calvin Cycle Fig. 8.5 -Splits water (yielding H +, e -, and O 2 ) -Produces ATP -Reduces NADP + to NADPH

11. 8-11 Light-Dependant ATP Production and the Electron Transport System Hydrogen builds up concentration gradient in the thylakoid space. The flow of H + through an ATP synthase complex back into the stroma drives the chemiosmotic production of ATP. Fig. 8.6

12. 8-12 Solar energy + 6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6O 2 Light-Dependant Reactions of Photosynthesis produce O 2, ATP, and NADPH – not glucose. ADP + P  ATP NADP + H  NADPH

13. 8-13 Carbohydrate Synthesis Light-independent reactions -NADPH and ATP  are used to reduce CO 2 to carbohydrate. -This occurs in the stroma of a chloroplast by a series of reactions called the Calvin cycle.

14. 8-14 Stages of the Calvin Cycle The Calvin cycle can be divided into: 1)Fixation of CO 2 ; 2)Reduction of CO 2 ; and 3)Regeneration of RuBP (ribulase biphosphate).

15. 8-15 The Calvin cycle (simplified) ATP ADP NADPH NADP C 6 H 12 O 6 RuBp 3CO 2 + 3RuBp (C 5 ) 6(C 6 ) 6PGA (C 3 ) 6PGAL (C3)

16. 8-16 The light-independent reactions of the Calvin cycle (detailed) From light- dependant reactions Fig. 8.8 From light- dependant reactions Fixation of CO 2

17. 8-17 Photosynthesis Efficiency Ideal laboratory conditions: 25% of solar energy transferred. Under natural conditions: the efficiency ranges from less than 1% to a maximum of 8%.

18. 8-18 CO 2 H 2 O Calvin CycleElectron Pathways Solar Energy RuBP PGAL ATP O 2 Glucose Aerobic Cellular Respiration in Mitochondria makes new ATP Light Independent ReactionsLight Dependant Reactions Photosynthesis in Chloroplast NADPH

19. 8-19 Photosynthetic organisms carry on both photosynthesis and cellular respiration and rely on solar energy. Solar Energy + CO 2 + H 2 0  C 6 H 12 O 6 + O 2 C 6 H 12 O 6 + O 2  CO 2 + H 2 0 + chemical energy(ATP) Non-photosynthetic organisms only carry on cellular respiration and must rely on an external source of energy. C 6 H 12 O 6 + O 2  CO 2 + H 2 0 + chemical energy(ATP)

20. 8-20 Figure 6.10 from Chapter 6

21. 8-21 Solar Energy O 2 and Glucose CO 2 Plant Cell Animal Cell Mitochondria (Respiration) Chloroplast (Photosynthesis)

22. 8-22 Other Types of Photosynthesis Plants are able to live under many environmental conditions in part because various modes of photosynthesis have evolved. The photosynthesis considered so far is called C 3 photosynthesis because a C 3 molecule is formed immediately following CO 2 fixation.

23. 8-23 C 3 Versus C 4 Photosynthesis C 4 plants fix CO 2 by forming a C 4 molecule prior to the the Calvin cycle. In C 4 plants, CO 2 is taken up in mesophyll cells, and then a C 4 molecule (oxaloacetate) is pumped into bundle sheath cells where it releases CO 2 to the Calvin cycle. Thus, O 2 cannot accumulate when stomata close.

24. 8-24 In C 4 plants, bundle sheath cells also contain chloroplasts, and mesophyll cells are arranged concentrically around bundle sheath cells:

25. 8-25 CAM Photosynthesis CAM plants also fix CO 2 by forming a C 4 molecule, but this occurs at night when stomata can open without water loss. CAM stands for crassulacean-acid metabolism after the Crassulaceae, a family of succulent plants from arid regions. C 4 represents a partitioning in space, whereas CAM is a partitioning in time.

26. 8-26

27. 8-27 Photosynthesis Versus Cellular Respiration Both plant and animal cells carry on cellular respiration in mitochondria; photosynthesis occurs in plant chloroplasts. Photosynthesis is the building up of glucose, while cellular respiration is the breaking down of glucose.