Daily Newsletter March 6, 2012

Daily Newsletter March 6, 2012

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Today's Topic: Photosynthetic Energy Harvesting

The chloroplast of the the plant has two know Photosystems: P680 (Photosystem II) and P700 (Photosystem I).

• Photosystem II
• Used to Generate ATP (chemiosmosis)
• Water is split to recharge the P680 reaction center with electrons and hydrogens.
• Donates electrons to Photosystem I
• Photosystem I
• Can operate either Cyclic or Non-Cyclic
• Non-Cyclic
• Excited electrons are given to NADP⁺
• Electrons accepted from Photosystem I to recharge the P700 reaction center. 
• Cyclic
• Excited electrons are used to make ATP (chemiosmosis)
•  Electrons are returned to Photosystem I (recycled) to recharge P700 reaction center.

Remember:  The photosystems are complex arrangements of chlorophyll pigments found in the thylakoid membrane.  When electrons are used to make ATP, the electrons will be passed between electron carriers that act as proton pumps.  The electrons are used to build and maintain a proton motive force, which will directly be used to make ATP.  So all electron movement is occurring due to electron carriers in the membrane.

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Daily Challenge:
Describe how the photosystems work to produce ATP and NADPH + H⁺. Remember with Photosystem I, you have both cyclic and non-cyclic operation.