Explain in detail How does the system regulate where the ele

Explain in detail How does the system regulate where the electrons go for cyclic vs. noncyclic electron transportation? In a dim light, which would be more predominant and why? (The answer must be in long paragraph form)

Solution

The photosystem II absorbs light, an electron excited to a higher energy level in the reaction center (P680) is captured by the primary electron acceptor. An enzyme extracts electrons from water and supplies them to P680, replacing the electrons that the chlorophyll molecule lost when it absorbs light energy. This reaction splits a water molecule into two hydrogen ions and an oxygen atom, which immediately combines with another oxygen atom to form O2. Each photoexcited electron passes from the primary electron acceptor in photosystem II to photosystem I via an electron transport chain. As the electrons move down the chain, their exergonic fall to a lower energy level is harnessed by the thylakoid membrane to produce ATP. The production of ATP in the chloroplast is called photophosphorylation because the energy harnessed in the process originally came from light. This process of ATP production is called non cyclic photophosphorylation.

Under certain conditions, the photoexcited electrons take an alternative path called cyclic electron flow which used photosystem I (P700) but not through P680. This process produces no NADPH and no O2 but it does make ATP. This is called cyclic photophosphorylation.