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