Cyclic Photosynthesis

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Cyclic Photosynthesis

• By Greg Adams, Mo , Dorothy, Krysten

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What is Photosynthesis?

• Photosynthesis - The process in green plants and
  certain other organisms by which carbohydrates
  are synthesized from carbon dioxide and water
  using light as an energy source
• 6H2O 6CO2 ----------gt C6H12O6 6O2

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The Process

• First a photon of light is captured by a pigment.
  The result of this primary photoevent is the
  excitation of an electron within the pigment.
• The excited electron energy is transferred to the
  reaction center which transfers an enegetic
  electron to an acceptor module, initiating
  electron transport
• The excited electrons are shuttled along a series
  of electron carrier modules embedded within the
  Photosynthetic membrane.

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The Process con't

• Several of them react by transporting protons
  across the membrane, generating a proton
  gradient, Eventually the electrons are used to
  reduce final acceptor, NADPH
• Finally the protons that accumulate on one side
  of the membrane now flow back across the membrane
  through ATP synthase where chemiosmotric
  synthesis of ATP takes place.

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The Process Pictures

• http//highered.mcgraw-hill.com/olcweb/cgi/pluginp
  op.cgi?itswf535535/sites/dl/free/0072437316
  /120072/bio12.swfCyclic20and20Noncyclic20Phot
  ophosphorylation

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Light Reactions

• Light strikes chlorophyll a in such a way as to
  excite electrons to a higher energy state
• Photophosphorylation refers to the use of light
  energy from photosynthesis to ultimately provide
  the energy to convert ADP
• The energy created is converted into adenosine
  triphosphate (ATP) and nicotine adenine
  dinucleotide phosphate (NADPH).
• This is done along an along an electron transport
  process

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Electron Transport Chain

• The excited electrons are shuttled along a series
  of electron carries molecules embedded within the
  photosynthetic membrane. Several of them react
  by transporting protons across the membrane,
  generating a proton gradient. Eventually the
  electrons are used to reduce a final acceptor,
  NADPH.

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Photosystem I

• Light absorbed by clusters of chlorophyll and
  other pigments
• They are made of 2 major components
• Reaction center- where chlorophyll takes the
  electron and than passes the excited electron to
  an acceptor
• Antenna Complex - The capture of light energy
  for photosynthesis is enhanced by networks of
  pigments in the chloroplasts arranged in
  aggregates on the thylakoids

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Pictures

• Antenna complex
• Photosystem I

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Pictures