Cyclic And Non-Cyclic Photophosphorylation MCQ - Practice Questions with Answers
Edited By admin | Updated on Sep 18, 2023 18:34 AM | #NEET
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34 Questions around this concept.
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EASYIn light reactions, plastoquinone facilitates the transfer of electrons from:
Which light range is least effective in photosynthesis?
Concepts Covered - 2
Light Reaction: Non-Cyclic Photophosphorylation
- It was discovered by Hill and Bandel.
- It is carried out by both PS-I and PS-II photosystems and the reaction centre is P700 and P680.
- As the name says, the electrons that are passed from the reaction centre are not returned to the same reaction centre after passing through various intermediates.
- The replacement of electrons that move from PS-II takes place due to the splitting of water molecules.
- The electrons that are needed to replace those that are removed from PS-I are provided by PS-II.
- The light energy of a specific wavelength is absorbed by the chlorophyll molecule and the accessory pigments.
- The pigments transfer their absorbed energy to the reaction centre of PS-II.
- PS-II gets photoexcited and these electrons are further accepted by Pheophytin (Chlorophyll without Mg).
- The electron passes through a series of electron carriers PQ, cytochrome b6f complex and plastocyanin.
- Plastocyanin is water-soluble, Cu containing protein that is present in the thylakoid lumen. It connects PS-II with PS-I.
- P700 extrudes the electron after absorbing light energy.
- The electron passes through a series of carriers.
- Ferredoxin and NADP-Reductase finally combine with NADP+ and is reduced to NADPH.H+ using H+ obtained from the stroma.
Light Reaction: Cyclic Photophosphorylation
- In cyclic electron flow, only Photosystem 1 is used in order to produce ATP as a product but does not create any NADPH or O2 as a byproduct.
- Only occurs when plant cells are in need of ATP.
- It was discovered by Frankel in Purple-Sulphur bacteria.
- As the light rays fall on the reaction centre, the chl a molecule gets excited and passes these electrons to the molecule that has the ability to get reduced i.e. molecule with greater redox potential.
- After losing the electron the photo centre becomes oxidized. The expelled electron passes through a series of carriers.
- The electrons are returned by plastocyanin (Pc) to the P700 pigment in the reaction centre to complete the cycle.
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Light Reaction: Non-Cyclic Photophosphorylation
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