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Photosynthesis Part Duex Photosynthesis Part Duex Presentation Transcript

  • Photosynthesis Part Duex
  • Believe it or not, we did the first three sections of chapter 7 already
    • 7.1 Autotrophs are the producers of the biosphere
    • 7.2 Photosynthesis occurs in chloroplasts
    • 7.3 Plants produce O 2 gas by splitting water
  •  
  • 7.4 Photosynthesis is a redox process
    • What’s a redox process?
    • Redox is short for “oxidation-reduction”
    • Oxidized = lose electrons
    • Reduced = gain electrons.
    Figure 7.4A Reduction Oxidation Figure 7.4B Oxidation Reduction
  • 7.4 Photosynthesis is a redox process
    • Water molecules are split apart and electrons and H+ ions are removed, leaving O2 gas
    • These electrons and H+ ions are transferred to CO2, producing sugar
    Figure 7.4A Reduction Oxidation Figure 7.4B Oxidation Reduction
    • Adenosine Triphosphate
    • Nicotinamide adenine dinucleotide phosphate
    • NADPH is an electron carrier (it can donate or accept electrons).
    7.5 Overview: Photosynthesis occurs in two stages linked by ATP and NADPH
    • The complete process of photosynthesis consists of two linked sets of reactions:
      • the light reactions and the Calvin cycle
    • The light reactions convert light energy to chemical energy and produce O 2
    • The Calvin cycle assembles sugar molecules from CO 2 using the energy-carrying products of the light reactions
    7.5 Overview: Photosynthesis occurs in two stages linked by ATP and NADPH
    • An overview of photosynthesis
    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
    • Certain wavelengths of visible light drive the light reactions of photosynthesis
    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
  • To Recap Pigments:
    • Chlorophyll a : directly involved in light reactions
    • Chlorophyll b : NOT directly involved in light reactions, but broadents the range of light a plant can absorb
    Carotenoids: pass energy to Chlorophyll a, can absorb and dissipate excessive light that would damage chlorophyll.
  • Figure 7.6B Light Chloroplast Reflected light Absorbed light Transmitted light
  • 7.7 Photosystems capture solar power
    • Photons are fixed quantities of light
    • Shorter the wavelength the greater the energy
    • Pigment molecules absorb photons of light.
    Figure 7.7B Primary electron acceptor Other compounds Chlorophyll molecule Photon
  • What’s in a photosystem? Figure 7.7C Primary electron acceptor Photon Reaction center PHOTOSYSTEM Pigment molecules of antenna
  • What’s in a photosystem?
    • Each of the many light-harvesting photosystems consists of:
      • an “antenna” of chlorophyll and other pigment molecules that absorb light
      • a primary electron acceptor that receives excited electrons from the reaction-center chlorophyll
    • How could you tell if the electrons in a photosystem are excited?
    Figure 7.7A Heat Photon (fluorescence) Photon Chlorophyll molecule
    • Fluorescence of isolated chlorophyll in solution