Name: photosystem ii and water splitting
Uploaded: 2019-03-11T09:21:12.000Z
Duration: 1 min 22 s
Channel: JoVE

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Photosystem II

В фотосистеме II, мультибелковом комплексе, фотоны поглощаются, и их энергия проводится через светособирающую часть многими связанными пигментными молекулами, такими как хлорофилл a b, и каротиноиды. Активное поглощение вырабатывает энергию, которая перенесена на пару молекул хлорофилла А, известного как P68o в центре реакции. Здесь два хлорофилла специализируются чтобы пройти окисление, где они отдают возбуждённый электрон первичной молекуле-акцептору электронов, в процессе, называемом фотоактом.Отсутствующий электрон затем заменяется разделением воды на два иона водорода и один атом кислорода, высвобождая два электрона, которые поставляются один за другим к центру реакции. Теперь электроны готовы к путешествию в цепи электронного транспорта к фотосистеме I.Кислород может сочетаться с ещё одним кислородом из воды, чтобы сформировать газ, который уходит в атмосферу, и накапливание ионов водорода внутри тилакоида создаёт градиент концентрации, где то, что находятся в зоне высокой концентрации, протекает через специализированный полупроницаемый белковый канал, который называется ATФ синтаза, в область низкой концентрации. в строме.Этот процесс называется хемиосмос, и создаёт энергию, позволяя ATФ синтазе прикрепить третью фосфатную группу в АДФ для создания энергетического продукта, ATФ.

<ol>
	<li>Саси, Шина, Джелли Венкатеш, Равья Фатолла Данеши и Майанк Ананд Гурурани. «Внешние белки фотосистемы II и их предполагаемая роль в устойчивости к абиотическому стрессу у высших растений». Растения 7, No 4 (декабрь 2018 г.): 100.</li>
	<li>Ямамото, Ясуси. "Контроль качества фотосистемы II: механизмы предотвращения и толерантности к световым и тепловым стрессам тесно связаны с текучестью мембраны тилакоидов." Frontiers in Plant Science 7 (2016).</li>
</ol>

Фотосистема ii

<h4>Обзор</h4>

Фотосистема II – это мультибелковый комплекс, встроенный в тилакоидную мембрану, где он собирает световую энергию. Молекулы хлорофилла передают энергию определенной паре молекул хлорофилла в центре реакции Фотосистемы II. Здесь молекулы хлорофилла теряют электрон (окисление), передавая его первичному электронному акцептору. Пожертвованные электроны проходят через электронную транспортную цепочку в Фотосистему I. Разделение молекулы воды высвобождает один атом кислорода, двапротона(H ) и два электрона. Электроны заменяют пожертвованные электроны у двух хлорофилловых молекулами в центре реакции. Атом кислорода немедленно реагирует с другим атомом кислорода, производя O2, который высвобождается в атмосферу. Протоны накапливаются и создают градиент концентрации через тилакоидную мембрану, которая управляет синтезом АТФ в процессе, называемом хемиосмозом.

<h4>Поглощение света в фотосистеме II</h4>

Мульти белковый комплекс Фотосистема II собирает фотоны и передает энергию через связанные с ней пигменты хлорофилл a и b, а также каротиноиды. Каротиноиды имеют защитную функцию, поскольку они помогают рассеять огромное количество энергии, взятой в том, что в противном случае может повредить ткани растения.

Энергия перемещается от молекулы хлорофилла к молекуле хлорофилла, пока не достигнет пары специализированных хлорофилла молекулы в регионе, называемом центром реакции. Центр реакции также известен как P680, так как он поглощает свет на длине волны 680 нм. Энергия достаточно сильна, чтобы сломать электрон из хлорофилла молекулы (окисления). Свободный электрон переходит к основной молекуле-приемнику электронов, в процессе, называемом фотоактом. Электрон хлорофилла а в центре реакции заменяется одним из двух электронов, которые высвобождаются при расщеплении молекулы воды.

<h4>Протонный градиент и генерация АТФ</h4>

Расщепление воды в Фотосистеме II также генерирует атом кислорода, который сочетается со вторым атомом кислорода. В результате O2 ускользает в атмосферу. Реакция также делает два протона (H) , которые создают и создают градиент концентрации для питания специализированных, полупроницаемых белковый канал называется АТФ синтазы. Процесс перехода протонов от высокой концентрации в тилакоидом, через канал к нижней области концентрации в строме называют хемиосмозом. Хемиосмоз создает энергию, которая позволяет синтазе АТФ прикрепить третью фосфатную группу к ADP, чтобы сформировать молекулу энергии АТФ.

Фотосистема II

Многобелковая комплексная фотосистема II (PS II) собирает фотоны и передает их энергию через связанные пигменты к своему реакционному центру, а также ...

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photosystem ii and water splitting

Photosystem II is a multi-protein complex that captures light energy and begins the flow of electrons in photosynthesis. It uses bound pigments to harvest photons and send that energy to its reaction center. From there, the energy continues through the electron transport chain and on to photosystem I.

The pigments in photosystem II include chlorophyll a, chlorophyll b, and carotenoids. They are arranged in two parts of the photosystem: the antenna complex and the reaction center. The antenna complex absorbs light and funnels that energy to the special chlorophyll pair in the reaction center.

Carotenoids also have a protective role. They help dissipate excess absorbed energy and reduce damage to plant tissue. In the reaction center, also called P680, a photon excites an electron in chlorophyll. The high-energy electron is released and passed to the primary electron acceptor.

P680 then replaces the lost electron by taking low-energy electrons from water splitting. Splitting one H2O molecule releases two electrons, two hydrogen atoms, and one oxygen atom. Two oxygen atoms from two H2O molecules join to form oxygen gas, which is released into the environment. The hydrogen ions also help build the proton gradient across the thylakoid membrane. That gradient is essential for ATP synthesis in the chloroplast.

Photosystem II and Water Splitting

what is photosynthesis?

Photosynthesis in Chloroplasts and Leaves

Photosynthesis happens in plants and in some bacteria. It is the process that captures carbon dioxide and solar energy to make glucose. Glucose stores chemical energy as carbohydrates. The overall biochemical equation is 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2. Photosynthesis also releases oxygen into the atmosphere and helps maintain Earth’s atmospheric oxygen content. Photosynthetic reactions take place in chloroplasts, which are specialized membrane-enclosed parts of the plant cell.

light as energy

How Plant Pigments Capture Light

Photosynthesis uses light energy from the sun, which is a form of electromagnetic radiation. The full range of possible wavelengths is called the electromagnetic spectrum. Light is made of photons, which are small packets of energy. Photons act like waves and are described by frequency, wavelength, and amplitude. Waves with higher frequencies carry more energy and have shorter wavelengths. Waves with lower frequencies carry less energy and have longer wavelengths. For most organisms,...

anatomy of chloroplasts

Chloroplasts and Photosynthesis in Plant Cells

Chloroplasts are the organelles where photosynthesis takes place in green algae and plants. They are also found in green stems and unripe fruit. In plants, mesophyll cells in the leaf contain the highest density of chloroplasts. Each chloroplast has a double membrane. The outer membrane faces the plant cell cytoplasm on one side and the chloroplast intermembrane space on the other. The inner membrane separates that narrow space from the stroma, which is the watery interior of the chloroplast.

photosystem ii

Photosystem II is a multi-protein complex that captures light energy and begins the flow of electrons in photosynthesis. It uses bound pigments to harvest photons and send that energy to its reaction center. From there, the energy continues through the electron transport chain and on to photosystem I. The pigments in photosystem II include chlorophyll a, chlorophyll b, and carotenoids. They are arranged in two parts of the photosystem: the antenna complex and the reaction center. The antenna...

photosystem i

Photosystem I and NADPH Formation

Photosystem I helps convert light energy into NADPH during photosynthesis. It works with photosystem II in the thylakoid membrane of the chloroplast, but it uses a different electron supplier and a different electron acceptor. Electrons excited in photosystem II move to photosystem I through an electron transport chain. That chain includes plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As the electrons travel between the two photosystems, they lose energy and must be...

the calvin cycle

Carbon Fixation in Photosynthesis

Photosynthesis uses light energy to turn carbon dioxide into carbohydrates. It also releases oxygen as a by-product. These products help support most food webs and make aerobic life possible. Photosynthesis has two main stages, and they happen in different parts of the chloroplast. The light-dependent reactions take place in the thylakoid membranes. Chlorophyll absorbs light energy there and helps split water molecules. This releases O2 and makes ATP and NADPH. The light-independent reactions...

c4 pathway and cam

Plant Carbon Fixation in Hot Climates

Plant carbon fixation in hot climates can follow the C4 pathway or the CAM pathway. These alternative pathways help some plants reduce energy loss from photorespiration. Photorespiration happens when oxygen levels are high and rubisco, the enzyme in the Calvin cycle, binds O2 instead of CO2. When that happens, photosynthesis slows and energy is used up. The C4 pathway is used by plants such as corn and sugarcane. In mesophyll cells, CO2 first joins with PEP, or phosphoenolpyruvate, through the...

key terms and concepts

Learn how photosystem II captures light, excites P680, splits water, releases oxygen, and helps build the proton gradient needed for ATP synthesis.

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Photosystem II and Water Splitting

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