5.2 Photosynthesis

Light Dependent Reactions

• Plants use PS 1 and PS 2 to produce ATP and NADH
• This is a 2-part process called non-cyclic phosphorylation

Non-Cyclic Phosphorylation

Photo-system II

• light energy hits P680 and excites an electron of reaction center chlorophyll a
• the e- is captured by primary electron accept-or which initiates ETC
• the e- lost by the chlorophyll a molecule in P680 are replenished by coupling the photooxidation of chlorophyll a to the photolysis of water
• a water-splitting complex in the thylakoid lumen splits water into oxygen, hydrogen ions (protons, H+), and electrons
• the oxygen is released into the atmosphere as a waste product. The electrons are used to replace the es lost by the P680 chlorophyll a
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Photo-system I