Question

Where does non cyclic photophosphorylation take place? Describe this process. Why is the process preferd to as non cyclic?​

Answer 1

Non-cyclic photophosphorylation takes place in the grans of chloroplasts.

1. *Photosystem II gets excited during absorption of light and transfers electrons to electron acceptor molecule. P680 becomes oxidising agent which splits one molecule of water to release oxygen. This light dependent splitting of water molecule is called as photolysis.  
2. *As the water molecule is broken, electrons are generated which are accpeted by P680 molecule to restore its electrons. Now primary electron acceptor is reduced after accepting electrons from P680.
3. *This reduced acceptor donates electrons to the other components of ETS.releasing energy in the form of ATP from ADP.
4. *Photosystem I is excited by absorbing light and gets oxidised. It transfers its electrons to primary electron acceptor which gets reduced. Oxidised P700 obtains electrons from photosystem II, reduced electron acceptor of photosystem I transfer electrons to ferredoxin and ferredoxin-NADP reductase to reduce NADP to NADPH2
5. There is a continuous flow of electrons from water to photosystem II to photosystem I and then to NADP. As these electrons are transferred, there is the formation of ATP from ADP.

The process of non-cyclic photophosphorylation occurs as follows: It begins with the absorption of light by P680 in PS II. The molecule gets excited and gives out an energy-rich electron which jumps into an orbit farther away from the atomic nucleus.

Answer 2

Explanation:

NADPH is formed on the stromal side of the thylakoid membrane, so it is released into the stroma. In a process called non-cyclic photophosphorylation (the "standard" form of the light-dependent reactions), electrons are removed from water and passed through PSII and PSI before ending up in NADPH.