chapters_13_14_15_outline2_spr09

chapters_13_14_15_outline2_spr09 - Aerobic respiration In...

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Aerobic respiration In aerobic respiration, the pair of electrons from NADH is passed through a series of intermediates to oxygen NADH is oxidized back to NAD+, oxygen is reduced to water Oxygen is the terminal electron acceptor. There are several types of intermediates that pass electrons from NADH to oxygen: flavoproteins cytochromes quinones iron-sulfur proteins These components make up an electron transport chain In prokaryotes, the ETC is in the in the cytoplasmic membrane In eukaryotes, the ETC is in the mitochondria. Electron transport chain- series of membrane associated electron carriers that carry electrons from the the primary electron donor to the terminal electron acceptor. During electron transfer, electron transport systems conserve some of the released energy for the synthesis of ATP. Electron transport chain Different organisms have different ETC Some have more than one for different growth conditions Electrons are passed from one compound to the next At each step, some energy from the electrons is used to push hydrogen ions across the cytoplasmic membrane into the periplasm or to the outside of the cytoplasmic membrane Hydrogen ion gradient/proton motive force/chemiosmosis This creates a hydrogen ion gradient across the cytoplasmic membrane Outside of CM is now more acidic and more positive than the cytoplasm This gradient is a source of potential energy ATPase (ATP synthase) ATPase- enzyme which adds a phosphate group to ADP to make ATP ATPase does this by allowing protons to cross back into the cytoplasm Energy is released by reducing the hydrogen ion gradient, this energy is used to make the high energy bond of ATP. Oxidative phosphorylation - process of using the hydrogen ion gradient to make ATP cytoplasm cytoplasmic membrane periplasm NADH + H + NAD + 2e - 2e - 2H + 2e - 2e - 1/2 O 2 H 2 O iron- sulfur protein quinone Cyt b Cyt o H + 2H + flavoprotein cytoplasm periplasm H + H + H + H + H + H + H + H + ATPase ADP + P i ATP H +
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Substrate-level vs. Oxidative Phosphorylation Substrate-level phosphorylation ATP is made by transferring a high energy phosphate group to ADP No proton motive force , no ATPase necessary Oxidative phosphorylation Energy from a hydrogen gradient is used to make ATP When does each one occur? Substrate level phosphorylation occurs during glycolysis and Oxidative phosphorylation occurs during the electron transport chain. So if an organism is growing by anaerobic respiration it can only make ATP by substrate level phosphorylation; whereas if it grows by respiration it makes ATP by both substrate level phosphorylation and oxidative phosphorylation. Anaerobic respiration: makes ATP by
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chapters_13_14_15_outline2_spr09 - Aerobic respiration In...

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