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Fotositema II
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Fotolisis del agua
Photosynthesis is vital to life on Earth.
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Photosynthesis occurs in all green plants and some algae.
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One of the first stages of photosynthesis involves Photosystem II.
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The oxygen we breathe is a product of the Photosystem II reaction.
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This animation will describe the processes that take place within this important complex.
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Photosystem II involves several key components, including
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photons, light-harvesting chlorophyll-binding proteins,
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a pair of chlorophyll molecules known as the P680 reaction center,
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pheophyton molecules, and plastiquinones,
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along with water and oxygen.
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The reaction center of Photosystem II consists of multiple proteins and pigment molecules.
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At the heart of the reaction center is a special pair of chlorophyll molecules, P680,
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which donate an electron to the electron transport system.
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In photosystem II, the electron is then passed to a pheophyton molecule.
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The electron is then passed to plastaquinone QA and then to plastaquinone QB.
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These plastaquinone molecules are embedded in the D2 and D1 proteins.
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Once QB has accepted two electrons, it then acts as a mobile carrier to the next component of the photosynthetic electron transport system.
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Electrons from water are then transferred to the P680 molecules that have lost their electrons in the process.
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Additional proteins are involved in splitting the electrons from water.
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And still other proteins are necessary to build the complete photosystem reaction center.
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Surrounding the reaction center are light-harvesting chlorophyll-binding proteins.
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These proteins provide a way to harness the unique energy contained in light.
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When one of the many photons of light flooding a leaf hits a chlorophyll molecule surrounding the reaction center,
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it creates resonance energy.
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You can think of this as vibrational energy.
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Here you can see the chlorophyll vibrating.
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That resonance, or vibrational energy, is then passed to a neighboring chlorophyll molecule.
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It is then passed through several chlorophyll molecules until it reaches the P680 reaction
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center.
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It is that energy that results in the loss of an electron from the P680 molecule.
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Now we can see how these processes work as a whole.
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First, a photon of light activates a chlorophyll molecule.
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The resonance, or vibrational, energy is transferred to the P680 molecules.
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An electron is lost from P680.
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It is then donated to QA, then to QB.
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The P680 molecules are then reduced by the addition of an electron generated by the splitting
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of water molecules at the oxygen-evolving complex.
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Since QB needs two electrons to become mobile, a second photon of light is required.
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The resonance energy is again transferred to the reaction center.
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An electron is lost from P680 and transferred via QA to the QB, which already contains one
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electron.
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The fully reduced QB is then transferred to the cytochrome B6F complex.
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The P680 molecules are again reduced by the oxygen-evolving complex.
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Here you can see water being split at the oxygen-evolving complex.
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Two water molecules must be split to provide electrons to reduce P680.
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The oxygen we breathe is a product of this water splitting process.
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- Idioma/s:
- Autor/es:
- Virtual Cell
- Subido por:
- Benito H.
- Licencia:
- Reconocimiento - No comercial - Compartir igual
- Visualizaciones:
- 384
- Fecha:
- 10 de septiembre de 2010 - 12:43
- Visibilidad:
- Público
- Enlace Relacionado:
- Benito Hernández Giménez
- Centro:
- IES MORATALAZ
- Descripción ampliada:
- El fotosistema I (PSI) y el fotosistema II (PSII) son los encargados de captar la luz y de emplear su energía para impulsar el transporte de electrones a través de una cadena de aceptores. El complejo antena de dichos fotosistemas atrapa fotones de la luz, elevando los electrones a niveles más altos que su estado cuántico fundamental, y esta energía se va transportando entre diferentes moléculas de clorofila por resonancia, hasta que en el centro del fotosistema II se produce la fotólisis del agua, rompiéndola en medio, originando O, 2 protones (H+) y dos electrones. El oxígeno se unirá con el sobrante de otra molécula de agua, para crear oxígeno atmosférico (O2); los protones translocados al interior del tilacoide contribuyen a crear un gradiente electroquímico, que será utilizado por la ATPasa, y los electrones repondrán la carencia electrónica de la clorofila original.
- Duración:
- 04′ 32″
- Relación de aspecto:
- 1.31:1
- Resolución:
- 1024x780 píxeles
- Tamaño:
- 22.83 MBytes