1. I. Photosynthesis  The process of converting light energy into chemical bond energy in the form of glucose  Supplies energy and oxygen to virtually all living things

2. II. Chloroplasts  The site of photosynthesis  Chloroplasts contain chlorophyll absorb light use energy to drive photosynthesis  Three functional parts inside the chloroplast

3. 1. Intermembrane Space  Chloroplasts is a double membrane  Intermembrane space separates the two membranes

4. 2. Thylakoid  Flattened membrane sacs inside chloroplast  Chlorophyll is found here  Light reactions take place here  Grana stacks of thylakoids

5. 3. Stroma  Fluid filled space that surrounds grana  Reactions that use chemical energy to convert carbon dioxide to sugar occur here  These are called dark-reactions

6. III. Light Reactions  Occur in the thylakoid membranes of chloroplasts  Light energy excites a pair of electrons  Electrons passed to different “carriers” – they lose a bit of energy at each step  Generate ATP (photophosphorylation) and NADPH as they give off energy  Give off oxygen as a by-product from splitting of water

8. IV. Noncyclic Electron Flow  Involve PS I and PS II  Occurs in thylakoids  Passes electrons continuously from water to NADP+  Produces ATP  Produces NADPH  Produces oxygen

9. V. Cyclic Electron Flow  Involves only PS I  Makes ATP  Does not produce NADPH or oxygen

10. Bottom Line:  Light reactions take energy from light and hold it for later use  Held in ATP and NADPH

11. VI. Calvin Cycle – the Dark Reactions  Carbon-fixation reactions that assimilate 6 Carbons into a carbohydrate  Occurs in the stroma  ATP and NADPH produced by light reactions are used in the Calvin cycle to turn carbon dioxide to sugar  NADPH provides the reducing power  ATP provides the chemical energy

12. More Calvin Cycle…  End product of the Calvin Cycle is a glucose molecule  Uses 18 ATP molecules and 12 NADPH molecules  3 CO2 + 6 NADPH + 5 H2O + 9 ATP → C3H5O3-PO32- + 2 H+ + 6 NADP+ + 9 ADP + 8 Pi

13. Bottom Line:  Water donates electrons  Light provides energy  CO2 provides the carbons for sugar

15. Photosynthesis As a Process  Water is split, oxygen is released, sugar gets made from CO 2  …mmmmm…. sugar

16. Energy for Photosynthesis  OIL RIG Oxidation is loss of electrons, reduction is gain of electrons Photosynthesis is an endergonic process: energy is required to reduce carbon dioxide to sugar  Light provides energy of electrons as they are moved from water to sugar

17. Energy for Photosynthesis (cont’d)  Water is split, electrons are transferred from the water to carbon dioxide (via NADPH), reducing it to sugar  There are two separate parts to photosynthesis  Light reactions (the “Photo”)  Calvin Cycle (dark reactions) – (the “synthesis”)

18. IV. Respiration – Returning the Energy  We digest sugar, and energy is released in the form of ATP.  Sugar gets oxidized (loses electrons) and the energy released makes ATP  This happens in all cells of plants, animals, and bacteria  The byproduct is CO2, which is then used to make new sugar through photosynthesis

19. PHEW! Take a breather!  On with Photosynthesis!!!

20. III. Photosynthesis As a Process  Light energy absorbed; CO 2 absorbed; O 2 released from water; sugar produced  Plants split the water to release Hydrogen to make NADPH  Plants absorb light to energize electrons in the thylakoid membrane  Sugars provide a more useful storage form for the energy in the electrons released from water

21. IX. The Good Stuff…  Light reactions take energy in as light and store it as ATP and NADPH  Dark reactions take the energy stored in ATP and NADPH to make sugar molecules *****We take glucose in and convert the energy in glucose back to ATP so our bodies can use it*****

22. X. Three Types of Plants  C3 plants: These include rice, wheat, beans  Most plants are C3 which means 3- phosphoglycerate is produced  C4 plants: crab grass and sugarcane, plants in hot regions  They make a 4 carbon compound prior to the Calvin Cycle  An adaptation for plants that grow in hot regions, when stomata are closed

23. X. Three Types of Plants (cont’d)  CAM plants: (crassulacean acid metabolism)  Occurs in many desert dwelling plants such as cacti  Open stomata at night instead of during the day. Carbon gets fixed at night.  The only difference in these plants is the time of carbon fixation; they still all use the Calvin Cycle to produce sugar from CO 2