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Photosynthesis: Alternative Pathways Photorespiration Occurs

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Photosynthesis: Alternative Pathways Photorespiration Occurs when Rubisco binds with O2 instead of CO2 RuBP + O2 Phosphoglycolate + 3-phosphoglycerate Decreases ... – PowerPoint PPT presentation

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Title: Photosynthesis: Alternative Pathways Photorespiration Occurs


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Compare and Contrast
Versus
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Photosynthesis Alternative Pathways
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C3 Plants
  • Cool, moist environments

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C3 Plants
  • Called C3 because the 1st organic product of
    the Calvin Cycle is a 3-C molecule
    (3-phosphoglycerate)
  • Rubisco catalyzes 2 reactions RuBP with CO2 or
    RuBP with O2

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Photorespiration
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Photorespiration
  • Occurs when Rubisco binds with O2 instead of CO2
  • RuBP O2 ? Phosphoglycolate 3-phosphoglycerate
  • Decreases production of sugars

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C4 Plants
  • Hot, dry environments

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C4 Plants
  • Spatial separation
  • Enzyme PEP carboxylase fixes CO2 into a 4-C
    compound oxaloacetate
  • Unique leaf anatomy Mesophyll cells surround
    Bundle Sheath cells
  • Mesophyll cells take in CO2
  • Calvin Cycle occurs within Bundle Sheath only

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C4 Plants
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CAM Plants
  • Hot, dry, arid environments

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CAM Plants
  • Crassulacean Acid Metabolism
  • Temporal separation
  • Night stomata open to allow in CO2
  • CO2 incorporated into organic acids and stored in
    vacuoles of mesophyll cells
  • Day stomata closed ? conserve H2O
  • Organic acids release CO2 for Calvin cycle

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C4 versus CAM
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Homework
  • Read pg 168-171
  • Questions p172 2,4,6
  • Cheat sheet for C4 and CAM plants only

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Venn Diagram
  • Read pg 179-180
  • Draw a Venn Diagram comparing the similarities
    and differences between cellular respiration and
    photosynthesis.
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