Is cyclic electron flow Photoprotective?

Is cyclic electron flow Photoprotective?

Cyclic electron flow (CEF) has been documented as a crucial mechanism for photoprotection in Arabidopsis and tobacco. We hypothesized that CEF plays an important role in protecting photosystem I (PSI) and photosystem II (PSII) against drought stress for resurrection plants.

What is a cyclic electron flow?

In cyclic electron flow (CEF), electrons are recycled around photosystem I. As a result, a transthylakoid proton gradient (ΔpH) is generated, leading to the production of ATP without concomitant production of NADPH, thus increasing the ATP/NADPH ratio within the chloroplast.

What uses cyclic electron flow?

In higher plants, the generation of proton gradient across the thylakoid membrane (ΔpH) through cyclic electron flow (CEF) has mainly two functions: (1) to generate ATP and balance the ATP/NADPH energy budget, and (2) to protect photosystems I and II against photoinhibition.

What are the products of cyclic electron flow?

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

Where does cyclic electron flow occurs?

The reactions involve two types of electron flow in the thylakoid membrane. While linear electron transport generates both ATP and NADPH, cyclic electron transport around photosystem I (PS I) is exclusively involved in ATP synthesis without the accumulation of NADPH.

What’s the difference between cyclic and noncyclic electron flow?

Cyclic photo-phosphorylation in photosynthesis light dependent reaction leads to the formation of ATP and NADPH, and the electrons go from water to PSII to PSI and eventually to NADPH. In non-cyclic photo-phosphorylation only some ATP is produced and the electrons go from PSII to PSI and back again.

How are cyclic and noncyclic electron flow different?

So in non-cyclic photophosphorylation, you make oxygen, from splitting the water molecule, you make ATP using the H+ ions and you make NADPH. In cyclic photophosphorylation, you only use photosystem I. There is no splitting of water – the electrons only come from the light harvesting complex.

How important is the cyclic electron flow to the process of photosynthesis?

The light reactions in photosynthesis convert light energy into chemical energy in the forms of ATP and NADPH. The role of cyclic electron transport around PS I is proposed to be essential for balancing the ATP/NADPH production ratio and/or for protecting both photosystems from the damage via stromal over-reduction1.

What is cyclic electron flow used for during the light reactions of photosynthesis?

What are the products of the cyclic electron flow during the light reactions of photosynthesis?

~ATP, oxygen, and NADPH are the products of the light-dependent reactions. ATP is made from the ATP synthase complex as protons flow down a concentration gradient. Oxygen is made from the photolysis of water. NADPH is made when the electrons reduce NADP.

Why is the cyclic pathway so important?

With the cyclic pathway, plants can save some time and energy. Since photosystem I is accepting electrons that are returned to it, it is not accepting electrons from the previous electron transport chain. Therefore, the first electron transport chain will be backed up, which means that photolysis will not occur.

What are two differences between cyclic and linear electron flow in photosynthesis?

In linear electron flow (unbroken arrows) energy from absorbed photons is used to oxidise water on the luminal face of photosystem II (PS II). In cyclic electron flow, energy from absorbed photons causes the oxidation of the reaction centre (P700) in PS I.