Photosystems - 680 Photosystem I evolved very early...

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Photosystems The closely packed pigment molecules and the reaction center form a unit referred to as an antenna complex . Photons of light that are picked up by any of the pigment molecules in the antenna pass their energy to nearby pigment molecules until it is eventually passed to a special molecule of chlorophyll a called the reaction center . The reaction center molecule becomes ionized and it loses its electron to an electron acceptor. This electron will need to be replaced. The antenna, the reaction center, and the electron transport molecules make up a photosystem. There are two kinds of photosystems in eucaryotes. The reaction center chlorophyll molecule of photosystem I absorbs 700 nm light best and is therefore called P 700 . The reaction center of photosystem II absorbs 680 nm light best and is called P
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Unformatted text preview: 680 . Photosystem I evolved very early; photosystem II evolved later. Details of the Light-Dependent Reactions Photosystem II The diagrams that follow are less magnified views of the chloroplast and thylakoid shown in the diagram above. The antenna shown above is represented by a single green circle below. Notice that there are two photosystems and therefore two antennas. The blue circles represent the electron transport system (discussed later). During the light reactions, pigment molecules within the P 680 antenna absorb a photon of light energy. The energy from that molecule is passed to neighboring molecules and eventually makes its way to the reaction center molecule as previously described. When the reaction center molecule becomes excited, it loses its electron to an electron acceptor....
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This note was uploaded on 12/15/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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Photosystems - 680 Photosystem I evolved very early...

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