Why non cyclic photophosphorylation does not take place in grana?
Non-cyclic phosphorylation takes place in lamella of grana.
Here is the detail.
Non-cyclic photophosphorylation take place in the grana lamellae or on the thylakoid membrane of choloroplasts.
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PSII absorbs 680 nm wavelength of red light, causing electrons to become excited and jump into an orbit farther from the nucleus.
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These electrons are then accepted by an electron acceptor, which sends them to an electron transport system. Here ADP is converted into ATP by the help of ATP synthetase enzyme.
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Electron transport system transfers the electrons to PSI.
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Electrons in PSI are simultaneously excited on receiving a wavelength of 700 nm. These electrons are again transferred to another electron acceptor having a greater redox potential.
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From the electron acceptor, electrons are transferred to the molecule of NADP+.
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Addition of these electrons reduces the NADP+ to NADPH+ H+.
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During this process, electrons move downhill, i.e., towards the systems at greater redox potential.
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The flow of electrons assumes the shape of the letter ‘Z’ when all carriers are placed according to their redox potential. Hence, the process is called Z scheme.
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Since the electrons lost by PSII do not come back to it, this process of formation of ATP is called non-cyclic photo-phosphorylation.
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