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# Light Reaction (Photochemical Phase) The image describes the light-dependent reactions of photosynthesis. It explains how light energy is converted into chemical energy in the form of ATP and NADPH. ## Light Reactions Include: * Light absorption * Water splitting * Oxygen release * Form...

# Light Reaction (Photochemical Phase) The image describes the light-dependent reactions of photosynthesis. It explains how light energy is converted into chemical energy in the form of ATP and NADPH. ## Light Reactions Include: * Light absorption * Water splitting * Oxygen release * Formation of ATP & NADPH ## The Electron Transport * When PS II absorbs red light of 680 nm wavelength, electrons are excited and transferred to an electron acceptor. * The electron acceptor passes the electrons to a chain of electron transport system consisting of cytochromes. * This movement of electrons is downhill in terms of redox potential. * The electrons are transferred to the pigments of PS I. * Simultaneously, electrons in PS I are also excited when they receive red light of 700 nm and are transferred to another acceptor molecule with a greater redox potential. * These electrons are moved to a molecule of NADP+, reducing it to NADPH + H+. * Transfer of electrons from PS II to PS I, and finally downhill to NADP+ is called the Z scheme, due to its zigzag shape. This shape is formed when all the carriers are placed in a sequence on a redox potential scale. ## Splitting of Water (Photolysis) * The water splitting complex in PS II is located on the inner side of the thylakoid membrane. * Water is split into H+, [O], and electrons. * 2H2O → 4H+ + O2 + 4e- * So PS II can continuously supply electrons by replacing electrons from water splitting. * Thus, PS II provides the electrons needed to replace those removed from PS I. * The protons (H+) are used to reduce NADP to NADPH. * O2 is liberated as a byproduct of photosynthesis. **Z scheme of light reaction:** A diagram illustrating the transfer of electrons in the light-dependent reactions. The diagram shows the path of electrons flowing through photosystem II (PS II), electron transport system, photosystem I (PS I), and ending in the reduction of NADP+ to NADPH. **Diagram Details:** The diagrams show the flow of electrons and the movement of protons (H+) between photosystems and an electron transport chain. Different components like photosystem II, photosystem I, electron transport system, and photosystem II are labeled. The diagram shows the inputs and products involved in the process. **Note:** Some components were incomplete in the image. The OCR was able to transcribe the information necessary to form complete sentences and tables.