How light arrives at the plant
- As sunlight falls on the plant, some wavelengths are absorbed. The others are reflected/transmitted.
- Pattern of absorption/reflection: dependent on the pigments.
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Chlorophyll and other photosynthetic pigments.
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How chlorophyll harnesses energy from sunlight
- Light harnessed by a photosynthetic pigment behaves as PHOTON PARTICLES.
- A QUANTUM is the fixed amount of energy that a photon contains.
- The shorter the wavelength the larger the photon.
- When a photon is absorbed the pigment's electrons gain energy, and are raised to a higher energy level. This makes the molecule very unstable.
- In a chloroplast the energy is passed to a PRIMARY ACCEPTOR MOLECULE.
- Molecule: reduced. Chlorophyll: oxidised.
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Arrangement of pigments in the chloroplast.
- Pigments clustered in the thykaloid membranes.
- Cluster called an ANTENNA COMPLEX.
- Light energy is channeled to just one molecule of chlorophyll a.
- Chlorophyll a and primary acceptor molecule: REACTION CENTRE.
- Reaction centre + light gathering molecules = photosystem.
- Photosystem 1 = P700. Chlorophyll a's maximum absorption.
- Photosystem 2 = P680.
- LIGHT DEPENDENT stage.
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