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Light-harvesting complexes of green plants


The light-harvesting complex or antenna complex is an array of protein and chlorophyll molecules embedded in the thylakoid membrane of plants, which transfer light energy to one chlorophyll a molecule at the reaction center of a photosystem

The antenna pigments are predominantly chlorophyll b, xanthophylls, and carotenes Chlorophyll a is known as the core pigment Their absorption spectra are non-overlapping and broaden the range of light that can be absorbed in photosynthesis The carotenoids have another role as an antioxidant to prevent photo-oxidative damage of chlorophyll molecules Each antenna complex has between 250 and 400 pigment molecules and the energy they absorb is shuttled by resonance energy transfer to a specialized chlorophyll-protein complex known as the reaction center of each photosystem[1] The reaction center initiates a complex series of chemical reactions that capture energy in the form of chemical bonds

For photosystem II, when either of the two chlorophyll a molecules at the reaction center absorb energy, an electron is excited and transferred to an electron acceptor molecule, pheophytin, leaving the chlorophyll a in an oxidized state The oxidised chlorophyll a replaces the electrons by photolysis that involves the oxidation of water molecules to oxygen, protons and electrons

Under changing light conditions, the reversible phosphorylation of light harvesting chlorophyll a/b binding proteins LHCII represents a system for balancing the excitation energy between the two photosystems[2]

The N-terminus of the chlorophyll A-B binding protein extends into the stroma where it is involved with adhesion of granal membranes and photo-regulated by reversible phosphorylation of its threonine residues[3] Both these processes are believed to mediate the distribution of excitation energy between photosystems I and II

This family also includes the photosystem II protein PsbS, which plays a role in energy-dependent quenching that increases thermal dissipation of excess absorbed light energy in the photosystem[4]

References

  1. ^ Voet and Voet, Donald and Judith G 2011 Biochemistry 4th Ed USA: Wiley p 906 ISBN 978-0470-57095-1 
  2. ^ Liu XD, Shen YG 2004 "NaCl-induced phosphorylation of light harvesting chlorophyll a/b proteins in thylakoid membranes from the halotolerant green alga, Dunaliella salina" FEBS Lett 569 1–3: 337–340 doi:101016/jfebslet200405065 PMID 15225658 
  3. ^ Andersson B, Yang DH, Paulsen H 2000 "The N-terminal domain of the light-harvesting chlorophyll a/b-binding protein complex LHCII is essential for its acclimative proteolysis" FEBS Lett 466 2–3: 385–388 doi:101016/S0014-57930001107-8 PMID 10682866 
  4. ^ Kramer D, Bassi R, Li XP, Gilmore AM, Caffarri S, Golan T, Niyogi KK 2004 "Regulation of photosynthetic light harvesting involves intrathylakoid lumen pH sensing by the PsbS protein" J Biol Chem 279 22: 22866–22874 doi:101074/jbcM402461200 PMID 15033974 

See also

  • Light-harvesting complexes


Light-harvesting complexes of green plants Information about

Light-harvesting complexes of green plants


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    Light-harvesting complexes of green plants beatiful post thanks!

    29.10.2014


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