1. Intro to Photosynthesis & the Light Reactions AP Biology Chapter 10.1-10.2

2. Learning Target 1 (10.1) I can describe how photosynthesis converts light energy into the chemical energy of food.

3. Quick Review: Obtaining Energy  Life on Earth is solar powered  Directly: autotrophs  Indirectly: heterotrophs

4. Chloroplasts  Photosynthetic prokaryotes lack chloroplasts  photosynthetic membranes = enfolded regions of the plasma membrane Key structures: o Stroma o Thylakoid o Grana

5. Photosynthesis  Equation:  Part I: Light Dependent Reactions (thylakoid membrane)  Part II: Light Independent Reactions (stroma) oxidation reduction

6. Plant Structure  Roots  Stems  Leaves  Epidermis  Waxy covering to prevent excess water loss  Mesophyll  Contains photosynthetic cells  Stoma  Openings for gas exchange  Guard cells control

7. Learning Target 2 (10.2) I can explain how the light reactions work to convert solar energy to the chemical energy of ATP and NADPH.

8. Light  Form of electromagnetic radiation  Energy is inversely related to its wavelength  Shorter wavelengths pack more energy  Visible light is 380-750 nm

9. Plants are green because…  Chlorophyll absorbs two wavelengths of light:  Blue (420 nm)  Red (660 nm)  Green light is reflected

10. Light Reactions Part of photosynthesis that prepares to make glucose

11. Photosystems  Photosynthetic units within chloroplast grana

12. Electron Carrier  NADP +  Same function as carriers in CR  Remember “P” for photosynthesis

13. Light Dependent Reactions – Non-cyclic (Linear) Electron Flow  Produces ATP and NADPH using Photosystems I & II

14. 1. Sunlight strikes the Photosystem II complex and excites electrons, eventually passing it to the primary electron acceptor 2. Excited electron splits H 2 O into H + ions and O 2 gas

15. 3. Electrons flow through a series of membrane proteins, pumping H + ions into the thylakoid space 4. Collection of H + ions pass back to stroma through ATP synthase in thylakoid membrane 5. ADP is converted into ATP

16. 6. Sluggish electrons receive another photon of light in PSI 7. Excited electrons are passed to NADP reducing it into NADPH

18. Light Reaction Summary  Reactants:  H 2 O  Light  NADP +  ADP + P i  Products:  O 2  NADPH  ATP

19. Light Dependent Reactions – Cyclic Electron Flow  Produces ATP only using photosystem I  Evolutionary “leftover” of photosynthetic bacteria?

20. Light Dependent Reaction Animation  http://highered.mcgraw- hill.com/olc/dl/120072/bio13.swf http://highered.mcgraw- hill.com/olc/dl/120072/bio13.swf