Photosynthesis

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Photosynthesis
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Photosynthesis in nature

• Autotrophs biotic producers make their own food
  photoautotrophs chemoautotrophs
• Heterotrophs biotic consumers obtain organic
  food by eating other organisms or their
  by-products (includes decomposers)

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Overview of Photosynthesis
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The chloroplast

• Sites of photosynthesis
• Double membrane
• Pigment chlorophyll (located in the thylakoid)
• Light dependent reactions occur in the thylakoid
• Light independent reactions occur in the stroma

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Pigments

• Chlorophyll pigments absorb blue and red but
  reflect green.
• Carotenoid pigments absorb violet and blue but
  reflect yellow, orange, and red.

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The Chloroplast
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Photosynthesis an overview

• The light-dependent reactions convert light
  energy into chemical energy (ATP).
• The molecules of ATP produced in the
  light-dependent reactions are then used to fuel
  the light-independent reactions that produce
  simple sugars.
• 6CO2 6H2O ? C6H12O6 6O2

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Light Dependent Reactions
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Light Dependent Reactions

• Located in the thylakoid membrane
• Pigment molecules are struck by light and give
  off an electron
• Excited e- is trapped by a primary e- acceptor
  and sent through the electron transport chain
• Electron transport produces ATP
• e- is replaced by splitting water (releases O2)

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Light Independent Reactions

• Also called the Calvin Cycle
• Occurs in the stroma of the chloroplast
• 3 molecules of CO2 are converted into
  glyceraldehyde 3-phosphate (G3P)
• G3P can then be used by the plant to make glucose
  and other organic compounds

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Calvin cycle
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How Autotrophs Use Intermediates and Products of
Photosynthesis

• Sugar phosphates are used as cellular fuel and as
  building blocks in synthesis of carbohydrates
• Sucrose is transported from leaves to all parts
  of the plant
• Starch is the main storage form of carbohydrate
  in plants

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A review of photosynthesis