can cyclic electron transport support photosynthesis alone

In plants, photosynthesis results in the production of ATP and NADPH by a two-step process known as noncyclic photophosphorylation. This problem has been solved! PGR5 is necessary to induce a ΔpH-dependent component of nonphotochemical quenching (NPQ) of chlorophyll fluorescence at a high light intensity and this qE mechanism dissipates excessively absorbed light energy safely as heat from photosystem II antennae. 1963, Munekage et al. sphaeroides. Chlorophylls alone do not account for the action spectrum of photosynthesis! See Answer. The main pathway depends on the PROTON GRADIENT REGULATION 5 (PGR5) protein, whereas the minor pathway is mediated by the chloroplast NADH dehydrogenase-like (NDH) complex. Cyclic electron flow (CEF) is a crucial component of photosynthesis in both plants and cyanobacteria. A) using mutated organisms that can grow but that cannot carry out cyclic flow of electrons and compare their abilities to photosynthesize in different light intensities B) using plants that can carry out both linear and cyclic electron flow, or only one or another of thee processes, and measuring their light absorbance Hydrogen sulfide (H 2 S) or thiosulfate (S2O2−3)(S2O32−) can serve as the electron donor, generating elemental sulfur and sulfate (SO2−4)(SO42−)ions, respectively, as a result. By continuing you agree to the use of cookies. The electron then passes to plastocyanin before returning to chlorophyll. Cyclic Electron Transport in Photosystem I. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Light adaptation of cyclic electron transport through Photosystem I in the cyanobacterium Synechococcus sp. Explain your answer. Likewise, cyclic electron transport is zero when its components are completely oxidized, since there are no electrons to cycle. The latter is essential for protecting PSI and the pgr5 mutant cannot survive the fluctuating light intensity. While the nature of the coupling and the structures of key components are now known, there has long been disagreement over pathways of electron transport. Want to see the step-by-step answer? This entire pathway is known as cyclic photophosphorylation. We propose that the cyclic … Explain your answer. Alternative photosynthetic electron transport pathways during anaerobiosis in the green alga, nicotinamide adenine dinucleotide (phosphate), Ribulose-1,5-bisphosphate carboxylase oxygenase. Introduction The photosynthetic reduction of 1 mol COZ requires that coupled electron transport … However, up to now, it was not clear how it differs … This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts. This process produces no NADPH and no O 2, but it does make ATP. When Photosystem (PS) II is inhibited, a cyclic electron flow around PSI operates transiently at a rate close to the maximum turnover of photosynthesis. If the answer is cyclic electron transport and cyclic electron transport pumps two protons for each electron (through the Q cycle operating alone), photosystem I must recycle one electron in five . ► The recently discovered monomeric plastidic NADPH-dehydrogenase Nda2 of Chlamydomonas is involved in non-photochemical PQ-reduction during photosynthetic hydrogen evolution. Cyclic phosphorylation takes place when there is a high … Can cyclic electron transport alone support photosynthesis? ► Research on photosynthetic hydrogen production by Chlamydomonas reinhardtii provided new insights into photosynthetic electron transport pathways. The lower anaerobic rates are accelerated by antimycin A … In intact spinach chloroplasts, aerobic rates of HCO/sub 3//sup -/ supported oxygen evolution in saturating light are several-fold higher than rates observed under near anaerobic conditions. Expert Answer . Biochimica et Biophysica Acta (BBA) - Bioenergetics, ; Cyclic photophosphorylation follows anoxygenic photosynthesis that predominantly occurs in photosynthetic bacteria like green sulfur and … The specific electron donors used by a given organism or photosystem can vary and will be discussed further below for photosystems I and II in plants. PGR5 has been reported as an important factor for the activity of the ferredoxin-dependent cyclic electron transport around PSI. Ion channels and transporters localized to the thylakoid membrane involve the regulation and form a regulatory network of photosynthesis with the CET machinery. Fig. Cyclic Electron Transport in Photosynthesis 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. PSI cyclic electron transport was first discovered in the 1950s, before the concept of linear electron transport was established (Arnon et al. Can cyclic electron transport alone support photosynthesis? The photoexcitation of the PSII reaction center leads to the charge separation of the reaction center Chl P680, with both product… Photosynthetic H 2-generation, which is carried out by some species of unicellular green algae, is another intriguing variation of photosynthesis, and research on this metabolism has contributed to the understanding of non-linear photosynthetic electron transport pathways like chlororespiration and cyclic electron flow. There is, theoretically, no net loss of electrons; they stay in the system. The reactions involve two types of electron flow in the chloroplast. Copyright © 2011 Elsevier B.V. All rights reserved. 2002).As previously reported (Munekage et al. Copyright © 2021 Elsevier B.V. or its licensors or contributors. While SHAM alone caused only a small inhibition ... Espie GS (2002. b) Mitochondrial-driven bicarbonate transport supports photosynthesis in a marine microalga. Cyclic electron transport will normally generate an electrochemical potential (typically pH) gradient across a membrane but does not result in the net production of reductant. In the simplest systems in prokaryotes, photosynthesis is used just for the production of energy, and not for the building of any biological molecules. 1 (A) Diagram of linear photosynthesis (solid arrows), respiration (dashed and dotted arrows), and cyclic electron transfer (dashed arrow) in cyanobacteria showing where DCMU and DBMIB block electron flow.In the thylakoid membrane of cyanobacteria photosynthesis and respiration are intermingled, while in the cytoplasmic membrane, only a respiratory pathway is present. Although the contribution of the NDH complex to the pmf formation is much smaller than that of the PGR5-dependent CET during steady-state photosynthesis, the NDH complex efficiently pumps protons probably in the absence of large pmf. Alternate cyclic electron transfer pathways involved in type I qE modulation Various light-driven cyclic electron transfer pathways have been mitochondria and bacteria [31,56– 67]. Ongoing research on plant and algal photosynthesis, supported … During photosynthesis of plants, sunlight causes many kinds of electron transport. In these systems there is a process called cyclic photophosphorylation, … The lumenal acidification also downregulates the electron transport at the cytochrome b6f complex. Its energy is absorbed by the light-harvesting Chl molecules in both PSI and PSII, and is then used for the excitation of both the reaction center Chls. Generalized model of electron transport-limited C 3 photosynthesis X. Yin et al. ► Starch is the major electron source for hydrogen production by sulfur deprived wild type Chlamydomonas cells, while in starchless mutants, photosystem 2 provides most of the electrons. Although it is still a topic of debate, as to whether PGR5 is really involved in CET, the Arabidopsis pgr5 mutant is severely defective in the ΔpH-dependent regulation of photosynthetic electron transport. Thus in order to keep generating NADPH there's needs to be a source of electrons … Volume 87, number 1 FEBS LETTERS March 1978 THE FUNCTION OF CYCLIC ELECTRON TRANSPORT IN PHOTOSYNTHESIS R. E. SLOVACEK, J. D. MILLS and G. HIND Biology Department, Brookhaven National Laboratory, Upton NY, USA Received 20 December 1977 1. Upon linear electron transport, electrons extracted from water are used to reduce NADP+ to NADPH. The products of non-cyclic photophosphorylation are ATP (generated by a build up of H+ inside the lumen of the thylakoids, which then drive ATP synthase) and NADPH (generated using the protein NADPH reductase at the end of the electron transport chain, where an e- reduces … The light energy of the sun is converted to electron flows in the photosynthetic electron transport system in chloroplasts. Median response time is 34 minutes and may be longer for new subjects. This NADPH will be used for carbon fixation. check_circle Expert Answer. Clearly, other pigments absorbing elsewhere in the visible spectrum also support photosynthesis. If the answer is pseudocyclic electron transport, 14% of electrons must end up on oxygen and not on NADP +. In addition to the size of pmf, it is also necessary to regulate the partitioning pmf components, ΔpH, and membrane potential (ΔΨ) across the thylakoid membrane. We use cookies to help provide and enhance our service and tailor content and ads. The high efficiency of the cyclic pathway implies that the cyclic and the linear transfer chains are structurally isolated one from the other. Photosynthesis Research 1995 , 46 (1-2) , 277-285. Can cyclic electron transport alone support photosynthesis? 2002), addition of 10 µM antimycin A to ruptured chloroplasts isolated from the wild type lowered PQ reduction activity, although the level was higher than in pgr5, probably because of incomplete inhibition (). Question: Can Cyclic Electron Transport Alone Support Photosynthesis? See the answer. The physiological … By continuing you agree to the use of cookies. While … *Response times vary by subject and question complexity. of cyclic electron transport in photosynthesis of Rb. In the unicellular green alga Chlamydomonas reinhardtii, this condition is induced by sulfur deficiency, and it results in the production of molecular hydrogen. Explain Your Answer. While linear electron transport generates both ATP and NADPH, photosystem I cyclic electron transport is exclusively involved in ATP synthesis. Median response time is 34 minutes and may be longer for new subjects. If the answer is cyclic electron transport and cyclic electron transport pumps two protons for each electron (through the Q cycle operating alone), photosystem I must recycle one electron in five . PCC 6803 mutants deficient in respiratory dehydrogenases. In non-cyclic photophosphorylation electrons are removed from the photosystem, as they end up in NADPH after moving through an electron transport chain (which does not pump protons- there's only so much you can ask from the energy of a single photon). When PSII is active, the cyclic flow operates with a similar rate during the first seconds of illumination. The oxygen molecule has been integrated into the cellular metabolism, both as the most efficient electron acceptor during respiratory electron transport and as oxidant and/or “substrate” in a number of biosynthetic pathways. Biochemistry (Moscow) 2011 , … Under certain conditions, the photoexcited electrons take an alternative path called cyclic electron flow, which uses photosystem I (P700) but not photosystem II (P680). Correspondence: Dr Xinyou Yin. Research on this biotechnologically relevant phenomenon has contributed largely to new insights into additional pathways of photosynthetic electron transport, which extend the former concept of linear electron flow by far. Check out a sample Q&A here. A study with barley … *Response times vary by subject and question complexity. Plant Physiol 130 284–291 [PMC free article] Igamberdiev AU, Hurry V, Kromer S, Gardestrom P (1998) The role of mitochondrial electron transport during photosynthetic induction. Photosynthesis: Plants can synthesize their food using light as the energy source, water as the electron donor, and carbon dioxide as the carbon source. A proton-motive force is produced throughout this electron transport chain which pumps H+ ions across the membrane and produces a concentration gradient that can be used to power ATP synthase during chemiosmosis. A proton-motive force is produced throughout this electron transport chain which pumps H+ ions across the membrane and produces a concentration gradient that can be used to power ATP synthase during chemiosmosis. Light-driven electron transport is coupled to ATP synthesis in chloroplasts. Cyclic photophosphorylation can define as the light reaction of the photosynthetic process, where the ATP produced couples with the electrons.

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