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

K12 Standards

Louisiana Student Standards for Science

High School

Environmental Science

Earth’s Systems

HS-ESS2-6

Photosystem II

- En el fotosistema II,
un complejo proteico,

los fotones son absorbidos
y su energía pasa

a través de la porción
del complejo recolector

por varias moléculas de pigmentos

como la clorofila a y
b y los carotenoides.

Esta absorción activa genera
energía que es transferida

a un par de moléculas de
clorofila a llamadas P680

en el centro de reacción.

Aquí las dos clorofilas se especializan

para someterse a la oxidación,

donde dan un electrón excitado

al electrón primario de
la molécula receptora

en un proceso llamado fotoacto.

Este electrón perdido es remplazado

al separa agua en dos iones de hidrógeno

y un átomo de oxigeno,
liberando dos electrones

que son suministrados uno por
uno al centro de reacción.

Ahora los electrones
están listos para viajar

a través de la cadena
transportadora de electrones

a el fotosistema I.

El oxigeno se puede combinar
con otro oxigeno de agua

para formar un gas que
escapa hacia la atmósfera

y la acumulación de iones de
hidrógeno dentro del tilacoide

crea una gradiente de concentración

por el cual aquellos en el área
de alta concentración fluyen

a través de un canal proteico
semipermeable especializado

llamado ATP sintasa, a un
área de baja concentración

en el estroma.

Este proceso se conoce como quimiosmosis

y crea energía, permitiendo
que la ATP sintasa

anexe un tercer grupo fosfato

al ADP para formar el
producto de energía ATP.

<ol>
	<li>Sasi, Shina, Jelli Venkatesh, Rawya Fatohllah Daneshi y Mayank Anand Gururani. "Proteínas extrínsecas del fotosistema II y su papel putativo en la tolerancia al estrés abiótico en plantas superiores". Plantas 7, no. 4 (diciembre de 2018): 100.</li>
	<li>"Control de calidad del fotosistema II: los mecanismos para evitar y tolerar el estrés lumínico y térmico están estrechamente relacionados con la fluidez de la membrana de los tilacoides". Frontiers in Plant Science 7 (2016).</li>
</ol>

fotosistema ii

El fotosistema II (PS II), complejo multiproteíco, recolecta fotones y transfiere su energía a través de sus pigmentos unidos a su centro de reacción y, en última instancia, al fotosistema I (PSI) a través de la cadena de transporte de electrones. Los pigmentos responsables de capturar la energía luminosa en los fotosistemas incluyen la clorofila a, la clorofila b, y los carotenoides. Las moléculas de pigmento están dispuestas en dos dominios del fotosistema, el complejo de antena y el centro de reacción. El objetivo principal de las moléculas de pigmento distribuidas en el complejo de antena es absorber la luz en forma de fotones y canalizarla hacia el par especial de clorofila del centro de reacción. Sin embargo, los carotenoides también cumplen una función protectora. Ayudan a disipar la gran cantidad de energía absorbida para evitar daños al tejido vegetal. El centro de reacción PSII, también conocido como P680, absorbe un fotón que excita un electrón en la clorofila. Los electrones de alta energía se liberan y pasan al aceptor de electrones primario. Los electrones faltantes del P680 oxidado se reemplazan extrayendo electrones de baja energía de la división de moléculas de agua. La división de una molécula de H2O libera dos electrones, dos átomos de hidrógeno y un átomo de oxígeno. Dos átomos de oxígeno de dos moléculas de H2O se combinan para formar una molécula de oxígeno que se libera al medioambiente. Por el contrario, los iones de hidrógeno liberados desempeñan un papel fundamental en el establecimiento de un gradiente de protones a través de la membrana tilacoide que es esencial para la síntesis de ATP en el cloroplasto.

Fotosistema II

El complejo multiproteico fotosistema II (PS II) recolecta fotones y transfiere su energía a través de sus pigmentos unidos a su centro de reacción, y ...

Education

Educación

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Biology

Biología

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Procesos celulares

Photosynthesis

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KEY TERMS AND CONCEPTS

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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

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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,...

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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

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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.

Photosystem II and Water Splitting | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

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JoVE Core Biología da vida a la biología a través de una serie con más de 300 lecciones de vídeo animadas, concisas y fáciles de entender, que explican conceptos clave de la biología, incluyendo también más de 150 vídeos de científicos en acción, que muestran experimentos reales realizados en laboratorios actuales de investigación.

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LS.4

LS.4.a

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From Molecules to Organisms: Structures and Processes

HS-LS1-5

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BIO.11

BIO.11.A

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ecosystems-interactions-energy-and-dynamics

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Photosystem II and Water Splitting

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