MICRB 265 (10/07/13) BIOENERGETICS - Part III - Metabolic Diversity (con't and end)

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Microbiology (Biological Sciences)
Brian Lanoil

MICRB 265 (October 7, 2013) BIOENERGETICS: Part III – Metabolic Diversity  Sulfur granules in sulfur bacteria act as e- storage Cyclic Phosphorylation  ATP is still synthesized via ATPase in the cytoplasmic membrane just like other bacteria  However, electrons are not sent to a terminal oxidase/reductase o They get recycled and their reduction potential is boosted in a reaction center by certain wavelengths of light o Electrons move within a closed loop and only leave to reduce NAD+ to NADH Cyclic Electron Flow: Anoxygenic Photosynthesis  Both purple nonsulfur and green sulfur bacteria implement cyclic electron flow o Electrons leave cycle to produce NADH  Purple nonsulfur have to do reverse electron flow in order to do this  In green sulfur bacteria, the electrons are boosted to a higher reduction potential (excited by a shorter wavelength) which will allow them to reduce NAD+ directly and without the need for reverse electron flow  Photosynthesis in plants is essentially a combination of purple non-sulfur bacteria and green sulfur bacteria’s reaction centers o Equivalent to the two photosystems found in photosynthesizing plant cells Oxygenic Photosynthesis  Creates O 2 electrons are from lysed water  Essentially two anoxygenic pathways put together  Water is so readily available that usually, cyclic e- flow is not necessary. o If water levels are low, then the plant cells will have to resort to cyclic e- flow since water is the electron donor  No oxygen is produced as a waste product in this type of photosynthesis Green Sulfur Bacteria  There are light AND dark reactions in this bacteria just like in photosynthesis  Analogous to aerobic photosynthesis o In green sulfur bacteria: H 2 oxidized to S by light o Aerobic photosynthesis: H O 2xidized to O by2light Organotrophic Photosynthesis: Purple Bacteria  Has light and dark reactions too  Non-sulfur bacteria o Organic carbon is e- donor  Electrons used for biosynthetic re
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