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  • Photosynthesis and Limiting Factors
    • Chloroplasts
      • Have  a thylakoid membrane folded into vesicles (thylakoids)
        • Stacked to form Grana
        • ContainsATP synthesis particals
      • Store products of photosynthesis as starch grains & Lipid droplets
    • Chlorophyll
      • Contain chlorophyll   a, b & other accessory pigments, absorb light at different wavelengths
        • Low absorption - cant be used.
        • Measure rate of photosynthesis using wavelengths gives action spectrum
      • arranged in photosystems
        • In the Thylakoid membranes
    • Light dependant stage
      • Thylakoid membrane
      • 1. Light energy splits water. H+ reduces NADP. e- excite electrons in PII, they go to electron carrier.
        • 2. Electrons down e.c.s where e- are lost to convert ADP+P -> ATP
          • 3. Light energy excites e- at PI, up to e.c. Some are recycled for more ATP
            • 4. Excited electrons down e.c.s to form NADP. Combine with H+ to create Reduced NADP
    • Light independent stage
      • Stroma
      • 1. CO2 binds to 5carbon RUBP to form 2 molecules of GP using rubisco
        • 2. GP is an acid, reduced & activated using ATP & R.NADP to form TP
          • 3. most TP  regenerates to RUBP using ATP. The rest leaves the cycle to form glucose
    • Factors affecting rate of photosynthesis
      • Measured by O2 released or uptake of CO2
        • Affected by respiration. Compensation point - photosynthesis & respiration are equal
      • Temperature
        • Most effects photosynthesis. above compensation point, plant loses mass - R greater than P
      • CO2 concentration
        • Substrate for rubisco. R not affected, P speeds up. Compensation level is low
      • Light intensity
        • Source of energy for P1. R not affected. P speeds up. Compensation point is low.
      • Time of day
        • Affects R & P by light & temp. Night - R exceeds P. Day - P exceeds R. 2 compensation points each 24hrs. Overall, P is greater than R so plant gains mass.
      • Limiting factors
        • Only 1 factor controlling rate, the furthest from optimum.
      • Uses for farmers and commercial growers
        • Can change conditions and consentrations to prevent/reduce limiting factors.


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