task In relation to Phototrophic metabolism, Anoxygenic photosynthesis -What is
ID: 268099 • Letter: T
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In relation to Phototrophic metabolism, Anoxygenic photosynthesis
-What is the purpose of anoxygenic photosynthesis from the point of view of the organism? What is the major difference between chemotrophic metabolism and photosynthesis in general?
-Give examples of prokaryotes that performs anoxygenic photosynthesis and classify these in the following scheme:
Energy source
Electron source
Carbon source
Chemo
Litho
Heterotroph
Photo
Organo
Autotroph
-Describe in details how light energy is used to drive ATP synthesis and generation of reducing power in a) Purple bacteria b) Green sulfur bacteria. Compare here briefly the differences/similarities in composition of the photosynthetic apparatus, mode of production of ATP and reduced electron carriers, electron donors and oxidation products.
-Describe how prokaryotes performing anoxygenic photosynthesis produce carbon based cell material and how this mechanism is coupled to the light reactions described in your answer to the question above.
-Discuss the eco-physiological advance/disadvance of the photosynthetic machinery in green sulfur bacteria vs. that in purple bacteria: Do you think that Purple bacteria are superior or inferior competitors for resources, such as light nutrients and carbon as compared to green sulfur bacteria?
Energy source
Electron source
Carbon source
Chemo
Litho
Heterotroph
Photo
Organo
Autotroph
Explanation / Answer
Anoxygenic photosynthesis is the process which doesn’t produce oxygen as final product, where it produces ATP from light energy hence it does not uses water as electron donor.
By chemotrophic metabolism cells catabolises nutrients nd conserve ATPand some of the free energy will be released as by product wherein in photosynthesis, it utilises water and carbon dioxide and in turn produces ATP which releases oxygen as by product.
Prokaryotes that perform anoxygenic photosynthesis are green sulphur bacteria, red and green filamentous prototrophs, archea bacteria, acidobacteria and helicobacteria.
Prokaryotes perform anoxygenic photosynthesis by using two reaction centres, In center one, when the light is obsorbed, p840 enters an excited state with large negative reduction potential so it donates electron to bacteriochlorophyll 663 which passes to the electron is chain. P840 regeneration is done by oxidation of sulphide ion from hydrogen sulphide. In center two, where reaction center bactetiochlorophyll 870 will b excited from the obsorption of light. Excited p870 donates electron to bacteriopheophytin. This creates electro chemical gradient and hence it generates ATP.
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