| Thylakoid |
Articles about Thylakoid |
Information AboutThylakoid |
| CATEGORIES ABOUT THYLAKOID | |
| membrane biology | |
| organelles | |
| photosynthesis | |
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Thylakoids contain many Integral Membrane Protein s that are important for photosynthesis. This includes two different Photosystem s with chlorophyll and accessory pigments to harvest light. Electron Transport Chains that function to generate a Chemiosmotic Potential across the membrane and NADPH , a product of the terminal Redox reaction. In addition, the ATP Synthase enzymes use the chemiosmotic potential to make ATP during Photophosphorylation . PHOTOSYSTEMS These photosystems are light-driven molecular units, each consisting of many Chlorophyll molecules and Accessory Pigment s bound to proteins in ''separate'' energy-absorbing Antenna Complex es. Each antenna complex has between 250 and 400 pigment molecules and the energy they absorb is shuttled by resonance energy transfer to a specialized chlorophyll ''a'' at the reaction center of each Photosystem . When either of the two chorophyll ''a'' molecules at the reaction center absorb energy an electron is excited and transferred to an electron-acceptor molecule. Photosystem I contains a pair of chlorophyll ''a'' molecules, designated P700, at its reaction center that maximally absorbs 700 nm light. '''Photosystem II''' contains P680 chlorophyll that absorbs 680 nm light best (note that these wavelengths correspond to deep red - see the Visible Spectrum ). The P is short for pigment and the number is the specific absorption peak in nanometers for the chlorophyll molecules in each reaction center. ELECTRON TRANSPORT CHAINS Two different variation of electron transport are used during Photosynthesis :
The noncyclic variety involves the participation of two different Photosystem s, while the cyclic is dependent on only one.
ATP SYNTHASE The molecular mechanism of ATP generation in chloroplasts is similar to that in , ADP + Pi is combined into ATP. SEE ALSO REFERENCES 1 |
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