8-2 Photosynthesis: An overview

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8-2 PhotosynthesisAn overview
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Photosynthesis

• When plants use energy from the sun to convert
  water and carbon dioxide into oxygen and
  high-energy carbs

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Van Helmonts Experiment

• In the 1600s, he designed an experiment to see
  if plants took material out of the soil to grow.
  
• Over 5 years, the mass of soil in a potted tree
  stayed the same.
• Concluded that the plant gained its mass from
  water only. (hydration)

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Priestleys Experiment

• In the 1700s Joseph Priestley Experimented with
  a light candle
• Covered a burning candle with a jarflame burns
  out.
• Candles need oxygen to burn!
• A mint sprig was placed under the jar with the
  candle and it remained burning.
• The plant produced oxygen for the flame!

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Jan Ingenhousz

• Proved that Priestleys results only occurred if
  a plant was exposed to light.
• In the presence of light, plants transform carbon
  dioxide and water into carbs and oxygen.

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Equation of Photosynthesis

• 6H2O 6CO2 ----------gt C6H12O6 6O2
• Water carbon dioxide (and light) ? sugar and
  oxygen
• six molecules of water plus six molecules of
  carbon dioxide produce one molecule of sugar plus
  six molecules of oxygen

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Light and Pigments

• Photosyntheis can only occur with the help of
  light and chlorophyll.
• Pigments are light absorbing molecules which
  gather the suns energy
• In plants, the pigment is called chlorophyll

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Chlorophyll a and b

• Chlorophyll a absorbs light from the violet and
  red regions of the visible spectrum
• Chlorophyll b absorbs light from the blue and red
  regions
• It does not absorb greenthis is why chlorophyll
  has a green color!