What does photosystem I generate during cyclic electron flow?
In cyclic electron flow, light energy harvested at photosystem I is used for ATP synthesis rather than NADPH synthesis (Figure 10.23). Electron transfer from photosystem I can thus generate either ATP or NADPH, depending on the metabolic needs of the cell.
What does cyclic electron transport result in?
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 does cyclic electron flow generate?
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 does non cyclic electron flow produce?
This cooperative process of energy production is called non-cyclic photophosphorylation and the transfer of electrons from water to NADPH, known as the Hill Reaction, is noncyclic electron flow. Light is absorbed at PS II, causing the photosystem to grab electrons from water and excite them to a primary acceptor.
What is the difference between cyclic and noncyclic electron flow?
Differentiate Between Cyclic and Noncyclic Photophosphorylation. In the cyclic photophosphorylation, only ATP is produced, whereas, in the non-cyclic photophosphorylation both NADPH and ATP are produced. In cyclic photophosphorylation, the electrons get expelled by photosystem I and they return to the system.
Which photosystem is used for cyclic 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.
What is the difference between linear and cyclic electron flow?
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.
Does cyclic photophosphorylation occur in low light intensity?
It takes place under the condition of low light intensity and light of wavelength lower than 680 nm and when CO2 fixation is inhibited. Plants are capable of producing energy by utilizing photons from sunlight through photophosphorylation.
Why is non-cyclic electron flow important?
Photophosphorylation refers to the use of light energy to ultimately provide the energy to convert ADP to ATP, thus replenishing the universal energy currency in living things.
Does cyclic Photophosphorylation occur in low light intensity?
Why is it called cyclic Photophosphorylation?
The photophosphorylation process which results in the movement of the electrons in a cyclic manner for synthesizing ATP molecules is called cyclic photophosphorylation. During cyclic photophosphorylation, the electrons are transferred back to P700 instead of moving into the NADP from the electron acceptor.
What is required for cyclic electron flow?
Cyclic electron transfer involves only PSI and cyt bf and was first described by Arnon (1). It involves electron flow to generate an electrochemical proton gradient across the thylakoid membrane without net production of reducing equivalents.
Where does chlororespiration take place in a plant?
Chlororespiration is a respiratory process that takes place within plants. Inside plant cells there is an organelle called the chloroplast which is surrounded by the thylakoid membrane. This membrane contains an enzyme called NAD (P)H dehydrogenase which transfers electrons in a linear chain to oxygen molecules.
How does chlororespiration take place in a lichen?
Gasulla, Casano and Guéra, concluded that the longer the lichen are subjected to darkness, the quicker the chlororespiratory pathways can begin. This is due to the fast depletion of PTOX molecules which reduce the PQ pool. These events then stimulate chlororespiratory ETCs into an ongoing loop until the lichen are placed in a luminous environment.
Where are the metabolic pathways found in chloroplasts?
Metabolic pathways responsible for photosynthesis are present in chloroplasts, whereas respiratory metabolic pathways are present in mitochondria. In these pathways, metabolic carriers (like phosphate) exchange NAD (P)H molecules between photosynthetic and respiratory ETCs.
