Details of the Light

Details of the Light - electrons from one carrier to...

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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. Photophosphorylation The electron transport system is found embedded within the thylakoid membrane and functions in the production of ATP. The system contains membrane-bound electron carriers that pass
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Unformatted text preview: electrons from one carrier to another. As a result of gaining an electron (reduction), the first carrier of the electron transport system gains energy. It uses some of the energy to pump H + into the thylakoid. The carrier then passes the electron to the next carrier. Because it used some energy to pump H + , it has less energy (reducing capability) to pass to the next H + pump. This carrier uses some of the remainder of the energy to pump more H + into the thylakoid. The electron is passed to the next carrier which also pumps H + . The electron transport system functions to create a concentration gradient of H + inside the thylakoid. The concentration gradient of H + is used to synthesize ATP. ATP is produced from ADP and P i when hydrogen ions pass out of the thylakoid through ATP synthase . This method of synthesizing ATP by using a H+ gradient in the thylakoid is called photophosphorylation ....
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Details of the Light - electrons from one carrier to...

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