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Cyclic Electron Flow in Cyanobacteria and Eukaryotic …

Johnson GN (2005) Cyclic electron transport in C‐3 plants: fact or artefact? Journal of Experimental Botany 56: 407–416.

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The Response of Cyclic Electron Flow around Photosystem …

During this conversion, the chlorophyll's electron flow can either be cyclic or non-cyclic.

The cyclic electron flow also called the , involves an electron transfer chain that starts from a pigment complex called in the chlorophyll.

In cyclic electron flow, the electron begins in a pigment complex called photosystem I, ..

Pathways of higher plant photosynthetic electron transport. Higher plant photosynthetic electron transport takes place in the chloroplast in the thylakoid membrane. Linear electron transport starts with the light‐driven splitting of water by photosystem II (PSII), producing oxygen and electrons. These are transferred via plastoquinone (PQ) the cytochrome b/f complex (cyt ) and plastocyanin (PC) to photosystem I (PSI). PSI then reduces ferredoxin (Fd) in a second light‐driven reaction. Ferredoxin may reduce NADP to NADPH, catalysed by ferredoxin NADP oxidoreductase (FNR) or pass electrons back to PQ, probably via the cyt b/f complex. NADPH may be used to produce carbohydrate in the Benson–Calvin cycle or may reduce PQ, via an NADP–PQ oxidoreductase complex (ndh). Electron transport is coupled to the transfer of protons from the chloroplast stroma to the thylakoid lumen. These return to the stroma via ATP synthase, a process coupled to the synthesis of ATP. The pH gradient produced may also lead to downregulation of light harvesting by PSII – a process termed qE.

This balancing may occur via cyclic electron flow around ..

Golding AJ and Johnson GN (2003) Down‐regulation of linear and activation of cyclic electron transport during drought. Planta 218: 107–114.

Harbinson J and Foyer CH (1991) Relationships between the efficiencies of photosystem‐I and photosystem‐II and stromal redox state in carbon dioxide‐free air – evidence for cyclic electron flow in vivo. Plant Physiology 97: 41–49.

Breyton C, Nandha B, Johnson GN, Joliot P and Finazzi G (2006) Redox modulation of cyclic electron flow around photosystem I in C3 plants. Biochemistry 45: 13465–13475.

Cyclic Electron Transport - eLS: Essential for Life Science

Munekage Y, Hashimoto M, Miyake C et al. (2004) Cyclic electron flow around photosystem I is essential for photosynthesis. Nature 429: 579–582.

Cyclic electron transport is a light‐driven flow of electrons through a photosynthetic reaction centre with the electrons returning to the reaction centre via an electron transport pathway. 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. The pH gradient generated may drive the production of adenosine triphosphate (ATP) (cyclic photophosphorylation) or may regulate photosynthesis.

The light-dependent reactions starts within Photosystem II. When the excited electron reaches the special chlorophyll molecule at the reaction centre of Photosystem II it is passed on to the chain of electron carriers. This chain of electron carriers is found within the thylakoid membrane. As this excited electron passes from one carrier to the next it releases energy. This energy is used to pump protons (hydrogen ions) across the thylakoid membrane and into the space within the thylakoids. This forms a proton gradient. The protons can travel back across the membrane, down the concentration gradient, however to do so they must pass through ATP synthase. ATP synthase is located in the thylakoid membrane and it uses the energy released from the movement of protons down their concentration gradient to synthesise ATP from ADP and inorganic phosphate. The synthesis of ATP in this manner is called non-cyclic photophosphorylation (uses the energy of excited electrons from photosystem II) .

Bendall DS and Manasse RS (1995) Cyclic photophosphorylation and electron‐transport. Biochimica et Biophysica Acta 1229: 23–38.
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  • Quantification of cyclic electron flow ..

    Cyclic Electron Flow in Anoxygenic Photosynthesis Cyclic Electron Flow in from BIO 2900 at Cornell

  • can go back to cytochrome bf in cyclic electron flow.

    19/03/2009 · Best Answer: To understand this you first must understand what cyclic electron flow is

  • Cyclic Electron Flow, C4 Plants, and CAM Plants

    flow along one of two pathways giving cyclic electron flow or noncyclic ..

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Activation of cyclic electron flow by hydrogen peroxide …

Munekage Y, Hojo M, Meurer J et al. (2002) PGR5 is involved in cyclic electron flow around photosystem I and is essential for photoprotection in Arabidopsis. Cell 110: 361–371.

LabBench Activity Plant Pigments and Photosynthesis

Moss DA and Bendall DS (1984) Cyclic electron transport in chloroplasts. The Q‐cycle and the site of action of antimycin. Biochimica et Biophysica Acta 767: 389–395.

IB Biology Notes - 8.2 Photosynthesis

Miyake C, Horiguchi S, Makino A et al. (2005) Effects of light intensity on cyclic electron flow around PSI and its relationship to non‐photochemical quenching of Chl fluorescence in tobacco leaves. Plant and Cell Physiology 46: 1819–1830.

Plant Energy Transformations-Photosynthesis - …

Laisk A, Eichelmann H, Oja V, Rasulov B and Ramma H (2006) Photosystem II cycle and alternative electron flow in leaves. Plant and Cell Physiology 47: 972–983.

Mono-cell Organisms - A Review of the Universe

Joët T, Cournac L, Peltier G and Havaux M (2002a) Cyclic electron flow around photosystem I in C‐3 plants. In vivo control by the redox state of chloroplasts and involvement of the NADH‐dehydrogenase complex. Plant Physiology 128: 760–769.

Photophosphorylation - Wikipedia

If the light intensity is not a limiting factor, there will usually be a shortage of NADP+ as NADPH accumulates within the stroma (see light independent reaction). NADP+ is needed for the normal flow of electrons in the thylakoid membranes as it is the final electron acceptor. If NADP+ is not available then the normal flow of electrons is inhibited. However, there is an alternative pathway for ATP production in this case and it is called cyclic photophosphorylation. It begins with Photosystem I absorbing light and becoming photoactivated. The excited electrons from Photosystem I are then passed on to a chain of electron carriers between Photosystem I and II. These electrons travel along the chain of carriers back to Photosystem I and as they do so they cause the pumping of protons across the thylakoid membrane and therefore create a proton gradient. As explained previously, the protons move back across the thylakoid membrane through ATP synthase and as they do so, ATP is produced. Therefore, ATP can be produced even when there is a shortage of NADP+.

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