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Phototrophs

Phototrophs. Photophosphorylation for ATP generation: still requires a PMF and ATP synthase, light as an energy input instead of NADH (or reduced inorganic compound) oxidation. Photosynthesis (photoautotrophs): Light Reactions Cyclic Photophosphorylation (Photosystem I = PSI)

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Phototrophs

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  1. Phototrophs • Photophosphorylation for ATP generation: • still requires a PMF and ATP synthase, • light as an energy input instead of NADH (or reduced inorganic compound) oxidation. • Photosynthesis (photoautotrophs): • Light Reactions • Cyclic Photophosphorylation (Photosystem I = PSI) • Non-Cyclic Photophosphorylation (Photosystem II = PSII) • Dark Reactions (Calvin Cycle) • Photopigments: • Chlorophylls; carotenoids; phycobiliproteins • Antenna (hundreds of pigment molecules to capture light) • Reaction-center chlorophyll (the link to electron transport)

  2. Chlorophylls Cyanobacteria and Eukaryotes have Chlorophyll a Green and Purple Bacteria have Bacteriochlorophylls The core is a tetrapyrole ring with a magnesium molecule.

  3. Prochloron and eukaryotes Accessory Pigments Eukaryotes alone Bind with proteins; cyanobacteria & red algae

  4. Different phototrophs have different pigments. • Pigments absorb light at unique wavelengths. • Wavelengths of light reaching an environment can be different. • Phototrophs best equipped to absorb available wavelengths in a given environment yield more energy.

  5. Cyclic Photophosphorylation(PS I) Absorbs wavelengths ≥680 nm (P700)

  6. Non-Cyclic Phosphorylation(PSII) Absorbs wavelengths ≤680 nm (P680)

  7. Z-scheme NADP+

  8. Green Sulfur Bacteria, Chlorobium Live in anoxic sulfide rich habitats. Sº accumulates outside the cell. Cyclic for ATP or non-cyclic to reduce NAD+.

  9. Green Non-Sulfur BacteriaThermophilic using organic matter for electron donor in photoheterotrphy; H2 for photoautotrophy (e.g. Chloroflexus).

  10. Purple Sulfur Bacteria • Live in sulfide rich and anoxic habitats. • Anoxygenic photoautotroph. • So accumulates intracellularly as inclusion bodies.

  11. Winogradsky column Purple Non-Sulfur, Rhodobacter Need a supply of organics or H2. Tolerates O2 or S-2. Some photoautotrophs.

  12. Phototrophy Overview Purple and Purple Non-Sulfur Bacteria require means of producing reduced electron carriers; done by reverse electron flow, as with chemolithoautotrophs. (or PMF)

  13. Carboxylation Phase Calvin Cycle Ribulose 1,5-bisphosphate Fixation of 3 Carbon Dioxide molecules to one molecule of Glyceraldehyde 3-Phosphate (G3P) via carboxylation & reduction requires 3 cycles. Each cycle requires regeneration of Ribulose 1,5-bisphosphate (RuBP) to fix the next CO2 via the enzyme RuBP Carboxylase. Regeneration of RuBP from 5 G3Ps follows a reversal of the PPP. 6 cycles will yield 2 G3Ps, which can form a hexose via Gluconeogenesis. Regeneration Phase Reduction Phase

  14. Anabolism

  15. Nutritional Types Revisited

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