o Photosynthesis generates O2 and organic molecules used in cellular

O photosynthesis generates o2 and organic molecules

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o Photosynthesis generates O2 and organic molecules (used in cellular respiration) o Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work. Catabolic processes yield energy by oxidizing organic fuels. Breakdown of organic molecules is exergonic Glycolysis (occurs with or w/o presence of O2) and fermentation (not O2 dependent) a partial degradation of sugars that occurs without O2 Cellular respiration (depends on presence of O2)- includes bother aerobic and anaerobic respiration but is often used to refer to aerobic respiration Aerobic respiration - consumes organic molecules and O2 yields most energy (ATP) o Aanaerobic respiration is similar to aerobic respiration but consumes compounds other than O2. Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with sugar glucose (oxidized) o Process includes a series of controlled steps which release energy as small portions for performing various types of cellular work. The energy stored in organic molecules is released by transfer of electrons (from high to low energy) during chemical reactions.
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Redox reactions - chemical reactions that transfer electrons between reactants Principle of redox 1) oxidation (reducing agent)- loses electrons 2) reduction (oxidizing agent)- gains electrons Oxidation of organic fuel molecules and stepwise energy harvest via NAH+ o During cellular respiration, fuel (such as glucose) is oxidized, and O2 is reduced o Electrons from organic compounds are first transferred to NAD+ (coenzyme) o As an electron acceptor, NAD+ functions as an oxidizing agent (reduced) during cellular respiration. o Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATP Ho NAD+ traps high energy electrons from glucose o Dehydrogenase (enzyme) removes two hydrogens from glucose (oxidizing it) o The enzyme delivers two electrons and one proton to its coenzyme, NAD+, reducing it to NADH => one proton released into environment o Electrons lose very little energy when transferred to NAD+ o NADH passes the electrons to the electron transport chain (ETC) o ETC passes electrons in a series of steps instead of one explosive reaction o O2 pulls electrons down chain in energy-yielding tumble => generates ATP Stages of Cellular Respiration (harvesting energy from glucose) o Glycolysis (breaks down glucose into two molecules of pyruvate o Pyruvate oxidation and the citric acid cycle (completes breakdown of glucose) o Oxidative phosphorylation: electron transport and chemiosmosis (accounts for most of the ATP synthesis) Glycolysis takes place is CTYOSOL Pyruvate oxidation and citric acid cycle occur in mitochondrial matrix.
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