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Photosynthesis

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  1. Photosynthesis Topic 8.2 AHL Photosynthesis

  2. Photosynthesis To put together Using light • Photosynthesis is a metabolic pathway consisting of light-dependent reactions. • Water and carbon dioxide are used to produce carbohydrates with oxygen as a waste product. Used in respiration, stored as starch or used to build cell walls as cellulose Split through photolysis in light dependent reactions. H+ ions used to generate ATP and NADPH Carbon is fixed in light independent reactions, using ATP & NADPH

  3. Chloroplast: The center of photosynthesis Chloroplast envelope (inner & outer membranes Stroma (70S ribosomes & naked DNA) Light independent Rxns. Thylakoid membranes Thylakoid stack (granum) Light dependent reactions

  4. What are these parts of a chloroplast? Granum (thylakoid stack) Chloroplast envelope stroma Thylakoid membrane

  5. Photosynthesis consists of light dependent and light independent reactions. Light Dependent Reactions Occur on the thylakoid membranes • Photolysis of water • Photophosphorylation • In: H2O NADP+ • Out: O2 NADPH Light independent Reactions Occur on the stroma of the chloroplast • Carbon fixation • Calvin cycle • Synthesis of carbohydrate • In: CO2, NADPH, • Out: Glucose, Phosphate, NADP+, &

  6. Light Dependent Reactions • Light energy is used to split water , releasing H+ which can be used by ATP synthase to produce ATP. • NADP+ is reduced to NADPH and H+ • ATP and NADPH are used in the light independent reactions. • Oxygen is a waste product.

  7. The action spectrum of photosynthesis is the range of wavelengths of light over which photosynthesis is most active.

  8. The action spectrum of photosynthesis is the range of wavelengths of light over which photosynthesis is most active. The absorption spectrum of chlorophyll corresponds with the action spectrum of photosynthesis.

  9. The action spectrum of photosynthesis is the range of wavelengths of light over which photosynthesis is most active. The absorption spectrum of chlorophyll corresponds with the action spectrum of photosynthesis. Peak of activity at 680 nm represents PSII Peak of activity at 700 nm represents PSI High energy blue light is also active in photosynthesis. Green light is not used so not absorbed by chlorophyll and therefore reflected.

  10. PSI & PSII consist of different proportions of chlorophyll a & b, which have slightly different absorption spectra

  11. IB Test Question: Explain the light dependent reactions of photosynthesis

  12. Great overview. Can you narrate it? That’s the real test! http://www.stolaf.edu/people/giannini/flashanimat/metabolism/photosynthesis.swf

  13. http://www.sumanasinc.com/webcontent/animations/content/harvestinglight.htmlhttp://www.sumanasinc.com/webcontent/animations/content/harvestinglight.html http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120072/bio13.swf::Photosynthetic%20Electron%20Transport%20and%20ATP%20Synthesis

  14. Compare the light dependent reactions of photosynthesis with the electron transport chain and oxidative phosphorylation of respiration. • Similarities: • Pump H+ ions into inter-membrane space to generate proton concentration gradient • Use electron transport to activate proton channels • Use ATP synthase to generate ATP • Use chemiosmosis of H+ ions to power ATP synthase • Use electron carriers • Differences: • Cell respiration • Electron carriers (NADH & FADH2) provide protons • Oxygen is terminal electron (and H+) acceptor, producing water as a waste product. • Does not use light • Uses cytochromes • Photosynthesis • Photolysis of water provides protons • NADP+ is terminal electron (and H+) acceptor, producing NADPH to be used in the Calvin cycle • Uses light • Uses photosystems http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120072/bio13.swf::Photosynthetic%20Electron%20Transport%20and%20ATP%20Synthesis http://highered.mcgraw-hill.com/olc/dl/120071/bio11.swf