Photosynthesis

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  • Created by: hsmith08
  • Created on: 21-04-15 18:43
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  • Photosynthesis
    • leaf is main photosynthetic structure
      • chloroplast is the cellular organelle
        • grana- stacks of 100 discs called thlakoids
        • thylakoids have chlorophyll
        • stroma- fluid filled matrix containing starch grains
      • large surface area to absorb lots of sunlight
      • arrangement of leaves minimises overlap
      • thin to keep diffusion distance short
      • transparent cuticle to let light through
      • packed with chloroplasts
      • numerous stomata for gas exchange
        • open and close in response to light
      • many air spaces for diffusion of gas
      • phloem and xylem
    • 6CO2+6H2O->C6H12O6+ 6O2
    • Light-dependent reaction
      • Oxidation-loss of electrons
        • Reduction- gain of electrons
      • Reduction- gain of electrons
      • chlorophyll molecule absorbs light energy which excites a pair of electrons
        • electrons leave chlorophyll and are taken up by a carrier
          • electrons passed a long carrier, losing energy at each stage
            • energy used to make ATP
      • chlorophyll replaces electrons by photolysis of water using light energy
        • produces protons taken up by NADP
      • thylakoids have a large surface area, proteins allow absorption of light, contains enzymes, DNA and ribosomes
    • Light-independent reaction
      • 1. carbon dioxide combines with RuBP using an enzyme
        • 2.2 molecules of glycerate-3-phosphate are produced
          • 3.ATP and NADPH are used to reduce GP to triose phosphate
            • 4. NADP re-formed and some glucose is made
              • 5. most RuBP is regenerated
        • diffuses from atmosphere and dissolves in water around walls of cells
      • stroma contains lots of enzymes, products from dependent can diffuse into gana, contains DNA and proteins
    • Limiting Factors
      • at any given moment, the rate of a reaction is limited by the factor that is at the least favourable value
      • increase in light intensity increases rate
        • compensation point-no net movement of gas
      • increase in CO2 increases rate
      • increase in temperature increases rate
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