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f) define the term photosynthetic pigment;
- Photosynthetic pigments are molecules that absorb light energy.
- Each pigment absorbs a specific wavelength of light in the visible light region
- Each pigment also has specific peak of absorption
- Wavelengths outside the range a reflected
- This reflected light is the colour which they appear to us as
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g) explain the importance of photosynthetic pigments in photosynthesis;
- Photosynthetic Pigments are held in place by proteins in the thylakoid membranes
- They are arranged in a funnel shape structure called a photosystem
- There are two type of pigments:
- Primary Pigments
- Structure:
- Consist of a long phytol chain and porphyrin group
- The porphrin group is similar to the haem group but contains Magnesium instead of Iron
- Consist of a long phytol chain and porphyrin group
- Light hitting the chlorophyll causes a pair of electrons belonging to Magnesium to become excited
- Primary pigments are Chlorophyll a and Chlorophyll b
- Chlorophyll a has two forms - P680 and P700
- They both appear yellow-green
- Each absorb red light at slightly different wavelengths
- Both also absorb blue light around the wavelength of 450 nm
- Both are found in the Primary Pigment Reaction Centre
- P680 is found in photosystem I
- P700 is found in photosystem II
- Chlorophyll b absorbs light around wavelength of 500 nm and 640 nm
- it appears blue-green
- Chlorophyll a has two forms - P680 and P700
- Structure:
- Accessory Pigments
- They absorb wavelengths that chlorophyll doesn't absorb well and pass the energy down to chlorophyll
- Carotenoid absorb blue light and reflect yellow and orange light
- Not directly involved in the light dependent reaction
- Do not contain the porphyrin (magnesium) group
- Carotene (orange) and xanthophyll (yellow) are the main carotenoid pigments
- Primary Pigments
Last active
August 29, 2015 14:01
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4.3.1 Photosynthesis Pigment
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