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Intro to Photosynthesis & the Light Reactions

Intro to Photosynthesis & the Light Reactions. AP Biology Chapter 10.1-10.2. Learning Target 1 (10.1). I can describe how photosynthesis converts light energy into the chemical energy of food. Quick Review: Obtaining Energy. Life on Earth is solar powered Directly: autotrophs

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Intro to Photosynthesis & the Light Reactions

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  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

  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)

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

  11. Photosystems • Photosynthetic units within chloroplast grana

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

  13. Sunlight strikes the Photosystem II complex and excites electrons, eventually passing it to the primary electron acceptor • Excited electron splits H2O into H+ ions and O2 gas

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

  15. Sluggish electrons receive another photon of light in PSI • Excited electrons are passed to NADP reducing it into NADPH

  16. Light Reaction Summary • Reactants: • H2O • Light • NADP+ • ADP + Pi • Products: • O2 • NADPH • ATP

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

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

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