ATP synthesis is driven by H+ gradient H+ gradient formation H+ H+ H+

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Presentation transcript:

Similarities between photophosphorylation and oxidative phosphorylation ATP synthesis is driven by H+ gradient H+ gradient formation H+ H+ H+ H+ H+ e- Proton pump e- e- ATP synthase Energy from electrons is used for H+ translocation ATP H+ ADP+Pi

Differences between photophosphorylation and oxidative phosphorylation Energy source: electrons NADH FADH2 Energy source: light H+ H+ H+ H+ H+ e- Proton pump NADP+ NADPH O2 H2O ATP synthase ATP H+ H+ By-product: water ADP+Pi By-product: electrons

(photophosphorylation) Photosynthesis: The light reactions (photophosphorylation)

Chlorophyll (or other pigments) absorbs light energy and conserve it as ATP and NADPH. Not all photosynthetic organisms use H2O as electron donor in photosynthesis; thus not all of them produce O2 while they produce ATP and NADPH. There are two types of photosynthesis: oxygenic (producing oxygen) photosynthesis and anoxygenic (not producing oxygen) photosynthesis. Only organisms with two photosystems can do oxygenic photosynthesis. At lease half of the photosynthsis in this world is done by microorganisms (algae, photosynthetic eukaryotes and photosynthetic bacteria).

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Outer membrane Thylakoid membrane (lamellae) Inner membrane grana lumen stroma

Chloroplast has photosystems with closely arranged chlorophyll

Cyanobacteria & red algae also contain similar structures called phycobilisome to facilitate light absorption p727

The major light absorbing pigment in higher plants Alternating single and double bonds give strong absorption in the visible light p726

The accessory pigment in bacteria and algae

What wavelength of light chlorophyll absorbs?

Chlorophylls can cover part of the spectrum – blue and red

The part of spectrum covered by chlorophylls coincides with the action spectrum of photosynthesis

Accessory pigment: the red-orange -carotene

Accessory pigment: lutein (the red-orange isoprenoid)

b-carotene and lutein can help plant absorb more light

Phycoerythrin and phycocyanin can absorb light that other pigments cannot absorb

Anoxygenic photosynthesis (ferredoxin) (pheophytin) (restore RC to original state) (restore RC to original state) (PSII) (PSI) p731

The Z scheme of oxygenic photosynthesis (special form of chlorophyll) (phylloquinone) (pheophytin) (plastoquinone) Green bacteria type Purple bacteria type p733

(A1)

PSI and PSII on thylakoid membrane are separated to prevent Excition Larceny LHCII holds grana together p736

Granal stacking by LHCII is regulated by light intensity High light [PQH2] [PQ] Low light [PQH2] [PQ] ATP Protein PPase Protein kinase LHCII -Thr-OH -Thr- P ADP Pi nonappressed appressed

Cytochrome b6f complex p737

Oxidative phosphorylation and photophosphorylation has something in common in cyanobacteria

Oxygen-evolving complex (water-splitting complex) D2 D1 QA QB Fe Pheo Pheo P680 e e e e Tyr e e e e Mn e e Mn 4H+ O2 e e e e e Mn e Mn 2H2O Oxygen-evolving complex (water-splitting complex) p739

N P p741

N N N p742

bacteriorhodopsin p744

All-trans-retinal 13-cis-retinol Proton transport

Chloroplast from higher plants is probably evolved from endosymbiotic bacteria (prochlorophytes) Chloroplast from red algae is probably evolved from cyanobacteria p1062

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