Photosynthesis Part Duex


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Photosynthesis Part Duex

  1. 1. Photosynthesis Part Duex
  2. 2. Believe it or not, we did the first three sections of chapter 7 already <ul><li>7.1 Autotrophs are the producers of the biosphere </li></ul><ul><li>7.2 Photosynthesis occurs in chloroplasts </li></ul><ul><li>7.3 Plants produce O 2 gas by splitting water </li></ul>
  3. 4. 7.4 Photosynthesis is a redox process <ul><li>What’s a redox process? </li></ul><ul><li>Redox is short for “oxidation-reduction” </li></ul><ul><li>Oxidized = lose electrons </li></ul><ul><li>Reduced = gain electrons. </li></ul>Figure 7.4A Reduction Oxidation Figure 7.4B Oxidation Reduction
  4. 5. 7.4 Photosynthesis is a redox process <ul><li>Water molecules are split apart and electrons and H+ ions are removed, leaving O2 gas </li></ul><ul><li>These electrons and H+ ions are transferred to CO2, producing sugar </li></ul>Figure 7.4A Reduction Oxidation Figure 7.4B Oxidation Reduction
  5. 6. <ul><li>Adenosine Triphosphate </li></ul><ul><li>Nicotinamide adenine dinucleotide phosphate </li></ul><ul><li>NADPH is an electron carrier (it can donate or accept electrons). </li></ul>7.5 Overview: Photosynthesis occurs in two stages linked by ATP and NADPH
  6. 7. <ul><li>The complete process of photosynthesis consists of two linked sets of reactions: </li></ul><ul><ul><li>the light reactions and the Calvin cycle </li></ul></ul><ul><li>The light reactions convert light energy to chemical energy and produce O 2 </li></ul><ul><li>The Calvin cycle assembles sugar molecules from CO 2 using the energy-carrying products of the light reactions </li></ul>7.5 Overview: Photosynthesis occurs in two stages linked by ATP and NADPH
  7. 8. <ul><li>An overview of photosynthesis </li></ul>Figure 7.5 Light Chloroplast LIGHT REACTIONS (in grana) CALVIN CYCLE (in stroma) Electrons H 2 O O 2 CO 2 NADP + ADP + P Sugar ATP NADPH
  8. 9. <ul><li>Certain wavelengths of visible light drive the light reactions of photosynthesis </li></ul>7.6 Visible radiation drives the light reactions THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY Visible light Wavelength (nm) Figure 7.6A Gamma rays X-rays UV Infrared Micro- waves Radio waves Chlorophyll a participates directly in light reactions Chlorophyll b does NOT participate in the light reactions
  9. 10. To Recap Pigments: <ul><li>Chlorophyll a : directly involved in light reactions </li></ul><ul><li>Chlorophyll b : NOT directly involved in light reactions, but broadents the range of light a plant can absorb </li></ul>Carotenoids: pass energy to Chlorophyll a, can absorb and dissipate excessive light that would damage chlorophyll.
  10. 11. Figure 7.6B Light Chloroplast Reflected light Absorbed light Transmitted light
  11. 12. 7.7 Photosystems capture solar power <ul><li>Photons are fixed quantities of light </li></ul><ul><li>Shorter the wavelength the greater the energy </li></ul><ul><li>Pigment molecules absorb photons of light. </li></ul>Figure 7.7B Primary electron acceptor Other compounds Chlorophyll molecule Photon
  12. 13. What’s in a photosystem? Figure 7.7C Primary electron acceptor Photon Reaction center PHOTOSYSTEM Pigment molecules of antenna
  13. 14. What’s in a photosystem? <ul><li>Each of the many light-harvesting photosystems consists of: </li></ul><ul><ul><li>an “antenna” of chlorophyll and other pigment molecules that absorb light </li></ul></ul><ul><ul><li>a primary electron acceptor that receives excited electrons from the reaction-center chlorophyll </li></ul></ul>
  14. 15. <ul><li>How could you tell if the electrons in a photosystem are excited? </li></ul>Figure 7.7A Heat Photon (fluorescence) Photon Chlorophyll molecule <ul><li>Fluorescence of isolated chlorophyll in solution </li></ul>