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Photosynthesis
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Photosynthesis

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  • 1. PHOTOSYNTHESIS and its relationship to cellular respiration
  • 2.
    • Process by which plants and other autotrophs convert the energy of sunlight into sugars.
    • Requires sunlight, water, and carbon dioxide.
    • Overall equation:
    • 6 CO 2 + 6 H 2 0  C 6 H 12 O 6 + 6 O 2
    • Occurs in the leaves of plants in organelles called chloroplasts.
    PHOTOSYNTHESIS IN OVERVIEW
  • 3. LEAF STRUCTURE
    • Most photosynthesis occurs in the palisade layer.
    • Gas exchange of CO 2 and O 2 occurs at openings called stomata surrounded by guard cells on the lower leaf surface.
    Palisade Spongy
  • 4. PHOTOSYNTHETIC ORGANISMS
    • Photosynthesis transforms solar energy
    • Organic molecules built by photosynthesis provide both the building blocks and energy for cells.
    • Plants use the raw materials: carbon dioxide and water
    • photosynthesis occurs in choloroplasts
  • 5. CHLOROPLASTS
  • 6. CHLOROPLAST STRUCTURE
    • Inner membrane called the thylakoid membrane .
    • Thickened regions called thylakoids . A stack of thylakoids is called a granum . (Plural – grana)
    • Stroma is a liquid surrounding the thylakoids.
  • 7. CHLOROPLASTS
    • Chlorophylls and other pigments involved in absorption of solar energy reside within thylakoid membranes of chloroplasts
  • 8. PIGMENTS
    • Chlorophyll A is the most important photosynthetic pigment.
    • Other pigments called antenna or accessory pigments are also present in the leaf.
      • Chlorophyll B
      • Carotenoids (orange / red)
      • Xanthophylls (yellow / brown)
    • These pigments are embedded in the membranes of the chloroplast in groups called photosystems .
  • 9. IT ALL STARTS WITH SUNLIGHT
    • This shows the visible light spectrum
    • Notice that different colors have different light wavelengths.
    • Pigments found in chlorophyll absorb various portions of visible light as seen in this absorption spectrum.
  • 10. IT ALL STARTS WITH SUNLIGHT
    • Two major photosynthetic pigments are
      • chlorophyll a
      • chlorophyll b.
    • Both chlorophylls absorb violet, blue, and red wavelengths best.
    • Very little green light is absorbed; most is reflected back; this is why leaves appear green.
  • 11. AUTUMN COLORS
    • Carotenoids are yellow-orange pigments which absorb light in violet, blue, and green regions.
    • When chlorophyll breaks down in fall, the yellow-orange pigments in leaves show through.
  • 12. TWO SETS OF REACTIONS
    • Occurs in two main phases.
      • Light reactions
      • Dark reactions (aka – the Calvin Cycle)
    • Light reactions are the “photo” part of photosynthesis. Light is absorbed by pigments.
    • Dark reactions are the “synthesis” part of photosynthesis. Trapped energy from the sun is converted to the chemical energy of sugars.
  • 13. TWO SETS OF REACTIONS
    • Light reactions cannot take place unless light is present. They are the energy-capturing reactions.
  • 14. LIGHT REACTIONS
    • Light-dependent reactions occur on the thylakoid membranes.
      • Light and water are required for this process.
      • Energy storage molecules are formed. (ATP and NADPH)
      • Oxygen gas is made as a waste product.
  • 15. DARK REACTIONS
    • Dark reactions (light-independent; Calvin cycle) occur in the stroma.
      • Carbon dioxide is “fixed” into the sugar glucose.
      • the ATP and NADPH molecules created during the light reactions power the production of this glucose.
  • 16.  
  • 17. THIS IS PRETTY HARD TO VISUALIZE, BUT THROUGH THE MAGIC OF TECHNOLOGY, WE CAN WATCH THESE PROCESSES AS ANIMATIONS
    • YouTube: The process of photosynthesis.
    • Forest biology – the overall process
    • McGraw Hill Animation

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