Light and Pigments

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Light and Pigments
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Properties of Light

• Part of the electromagnetic spectrum
• Travels as waves
• Light is composed of photons
• Particles of energy
• Energy is inversely proportional to wavelength

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Electromagnetic Spectrum
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Chloroplasts

• Found mainly in cells of mesophyll
• Double membrane
• Inner membrane surrounds fluid-filled stroma
  contains enzymes for carb production
• Within stroma is 3rd system of membranes forms
  thylakoids

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• Thylakoid membrane encloses thylakoid lumen
• Thylakoids may be arranged in stacks called grana
• Thylakoid membrane involved in ATP synthesis

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Pigments

• Substances that absorb visible light
• Different pigments absorb different wavelengths
• Wavelengths not absorbed are reflected or
  scattered thats the color you see

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• When photon strikes an atom/molecule, electron
  may move to a higher energy level
• http//earthguide.ucsd.edu/earthguide/diagrams/abs
  orption/absorption.html
• Electron can either
• Return to ground state
• Leave atom and transfer to carrier molecule

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Chlorophyll is main pigment of photosynthesis

• 2 main parts
• Ring
• H-C tail
• Several kinds
• Chlorophyll a main one
• Absorbs light in red and blue regions of spectrum

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Absorption of chlorophyll
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Accessory pigments

• Chlorophyll a (bright green) initiates
  light-dependent reactions of photosynthesis,
  other pigments participate as well
• Accessory pigments
• Chlorophyll b (yellow-green)
• Carotenoids yellow and orange

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Action spectrum

• Graph of effectiveness of different wavelengths
  of light