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Download RESPIRATION Production of ATP and CO2 by O2 and organic
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RESPIRATION Production of ATP and CO2 by O2 and organic molecules delivered through bloodstream Living is work E = capacity to do work Two characteristics of living things: - Use of E - Organization E required for these 2 characteristics comes from sun E captured in Photosynthesis Autotrophs (Gr. Self feed) perform Photosynthesis Heterotrophs (Gr. Other feed) rely on Autotrophic production Metabolism: sum of reactions taking place in cells Anabolism: building of larger molecules using E Catabolism: breaking down larger molecules and releasing E Aerobic: in the presence of O2, ½ O2 is final e- acceptor Anaerobic: in the absence of O2 Oxidation: removal of eReduction: addition of eC6H12O6 +6O2 6CO2 + 6H2O + E (ATP + Heat) This is typically how Respiration (and Photosynthesis) is represented Oxidation of sugar, Reduction of molecular oxygen But is a much simplified representation “The process is complex and challenging to learn.” The objective is an understanding of how cells use E stored in food to make ATP ATP is a loaded spring (potential chemical E) Release of this spring often results in Phosphorylation of compounds ATP is generated in Respiration Through a series of Oxidation – Reduction Reactions of large Organic Molecules Aka redox Occurs as organized Covalent C – H bonds are oxidized and their E captured These bonds represent the “hilltop” as Respiration proceeds “downhill” Toward very electronegative ½ O2 Respiration takes the E out of storage in these Covalent Bonds In sugar, starch, glycogen, fat, protein NAD+ is Respiratory Electron Carrier Reduced NADH results from addition of 2 e- and 1 H+ Contains nearly all the energy from the original organic molecule bond Key: Ea keeps us from burning up Without it, all these reactions would occur spontaneously Exergonic, releases E, negative delta G Consider burning a tank of gas all at once e- carriers and stepwise oxidation capture this E in an organized fashion Remember organization requires E Respiration has Three Major Steps 1) Glycolysis In cytoplasm Breaking Organic Molecule into 2 3-Carbon Pyruvate molecules Produces 2 NADH and 2 ATP This is NET; Remember Ea, Costs 2 ATP to overcome and 4 ATP formed NO CO2 released 2a) Prep Reaction carries Pyruvate into Mitochondrion, oxidized to Acetyl CoA ACoA is an Unstable Two Carbon Compound CO2 is released Happens Twice because Two Pyruvates produced 2) Krebs Cycle (Hans Krebs, 1930’s) Occurs in Mitochondrial Matrix Aka TCA Cycle, Citric Acid Cycle Occurs Twice, Once for each AcoA produced above Produces 2 CO2, 3 NADH, 1 FADH2, 1 ATP PER CYCLE Substrate Level Phosphorylation Direct formation of ATP by transfer of P group from intermediate substrat 3) Electron Transport Chain Occurs on Cristae Pair of High E e- from NADH are carried “downhill” through path in Redox Produces 5 ATP 3 from NADH 2 from FADH2 Because it enters chain “lower” Oxidative Phosphorylation: ATP production in presence of O2 O2 as terminal e- acceptor: e- from 2 NADH reduce 1 O2 to 2H2O Chemiosmosis Production of Steep Electrochemical Gradient with Proton Pump H+ produced during e- Transport are moved from inner membrane of cristae To intermembrane space, creating gradient Produces bulk of Aerobic Respiration ATP So, anaerobic respiration not nearly as efficient ATP Bookkeeping: bear in mind that these are rounded figures 39% efficiency yea! That’s Aerobic Respiration Fermentation Anaerobic respiration Pyruvate from Glycolysis Oxygen debt, can’t remove lactate as fast as it’s produced, delta pH 2% efficiency Other Respiratory Substrates Glucose was our example Fat Glycerol + 3 Fatty Acids Glycerol (3 C cmpd) can enter Glycolysis FA can be broken down into ACoA and enter Krebs Cycle Proteins can be catabolized and enter Respiration at various points Must be broken down into AA, and then deaminated Amine (N) group removed Anabolism Respiratory substrates and products can be used to form Macromolecules Glycerol fat Amino acids protein (Essential AA cannot be produced by humans)