Chloroplasts, Pigments and Photosynthesis

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Chloroplasts, Pigments and Photosynthesis
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What role do chloroplasts have in photosynthesis?

• Chloroplasts are the site where chemical
  reactions that make up the process of
  photosynthesis occur

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• Chloroplasts are the plant cell organelle that
  contain chlorophylls and other pigments
• Chlorophyll a is the primary photosynthetic
  pigment
• Chlorophyll b is an accessory pigment
• Both chlorophylls absorb red and blue light
  reflect green light

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• Other accessory pigments include
• Carotenoids reflect red and orange light
• Xanthophylls reflect yellow light

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Pigments and Light

• When wavelengths of visible light (white light)
  strikes a pigment, various wavelengths can be
  reflected, transmitted, or absorbed by the
  pigment

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• Reflected the light energy bounces back away
  from the pigment and can be seen (plants appear
  green to us)
• Transmitted the light passes through the pigment
  and its energy is not used
• Absorbed the pigment captures a specific
  wavelength of light energy

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What happens when light energy is absorbed by
pigments?

• Light energy absorbed by a pigment excites
  electrons in the thylakoid membrane of the
  chloroplasts

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Electromagnetic Spectrum
Chlorophyll a has an absorption peak of 665 Nm
and 465 Nm
Chlorophyll b has an absorption peak of 640 Nm
and 450 Nm
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Pigments and absorption