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Chapter 6

BIOL 1000 Chapter 6 - Cellular Respiration.docx

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BIOL 1000
Jennifer Steeves

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6.1 – The Chemical Basis of Cellular Respiration • Glucose, like gasoline, is a good fuel because of the presence of C–H bonds  Contains electrons that can be easily removed and used to do the work • Redox Reactions – Partially transfer electrons from donor to acceptor electrons  OIL RIG – donor is oxidised and acceptor is reduced • Cellular Respiration – The process of transferring electrons from donor organic molecules to a final acceptor molecule such as oxygen; redox reaction  The energy that is released drives ATP synthesis  Almost all organisms obtain energy for cellular activities; plants undergo it as well.  C H 6 1266  6CO2+ H O 2 ATP2+ Heat 6.2 – Cellular Respiration: An Overview 1. Glycolysis  Glucose is converted into two molecules of pyruvate 2. Pyruvate Oxidation & The Citric Acid Cycle  Pyruvate is converted into an acetyl compound that is oxidized completely to CO 2 3. Oxidative Phosphorylation (OP)  High-energy electrons produced form the first two stages pass along an ETC, with the energy released being used to establish a proton gradient across the membrane.  This gradient is used to synthesize ATP; ADP + inorganic phosphate by ATP synthase • Both Eukaryotes and Prokaryotes may undergo cellular respiration • In Eukaryotes most of cellular respiration occur in mitochondria • Series of Chemical Reactions and electron exchanges that convert glucose into ATP  Can transfer more of the energy stored in glucose into ATP if done in a series 6.3 – Glycolysis: The Splitting of Glucose • Occurs in the cytosol • Glucose (6 Carbons) is oxidised into two molecules of Pyruvate (3 Carbons each) • Electrons removed in the oxidation are delivered to NAD , producing NADH • Net Gain: 2 ATP + 2 NADH + 2 Pyruvate molecules for each molecule of Glucose oxidised • ATP molecules produced in energy-releasing steps of glycolysis result from substrate- level phosphorylation – an enzyme-catalyzed reaction transfers a phosphate group from a high-energy substrate to ADP 6.4 – Pyruvate Oxidation and the Citric Acid Cycle Pyruvate Oxidation • Pyruvate moves out of the cytosol into the Matrix; occurs inside mitochondrial matrix • One Pyruvate (3 Carbons) is oxidised to one acetyl group (2 Carbons) and 1 CO 2  Decarboxylation removes the Carbon, and it is released as carbon dioxide + • Electrons removed in the oxidation are accepted by 1 NAD to make 1 NADH; dehydrogenation • The acetyl group is transferred to coenzyme A, which carries it to the citric acid cycle 1. Decarboxylation of Pyruvate 2. Dehydrogenation of Acetate 3. Addition of Coenzyme A Citric Acid Cycle • Occurs in the mitochondrial matrix • 8 enzyme catalysed reactions 1. Acetyl group (2 Carbons) added to Oxaloacetate (4 Carbons) to create citrate (6 Carbons) 2. Citrate (6C) molecule rearranged to isocitrate (6C) by isomerase 3. 2 Electrons and protons transferred to NAD to create NADH + H by dehydrogenase  1 Carbon is released and added to O to pr2duce CO which i2 released 4. CoA-SH (cleaved from acetyl CoA) added creating a high energy bond 5. CoA-SH is released and a phosphate added (P) to tie carbon molecule (not shown)  Creating a high-energy phosphate bond 6. 2 electrons and 2 protons transferred to FAD to produce FADH by d2hydrogenase 7. Water added, we have 4 carbons, just a rearrangement of bonds 8. 2 electrons and hydrogen transferred to NAD to produce NADH + H by + dehydrogenase  Oxaloacetate reproduced • Acetyl groups are completely oxidised to CO 2 • Electrons removed in the oxidation are accepted by NAD or FAD • Substrate-level phosphorylation produces ATP • 2 CO 2 1 ATP, 3 NADH, and 1 FADH are 2roduced for each acetyl group oxidised 6.5 – Oxidative Phosphorylation: Electron Transport and Chemiosmosis • Series of integral proteins that, located in the inner membrane of the mitochondrion • Involved in transferring protons from the matrix to the inter membrane space; proton gradient • Electrons are passed from NADH and FADH to th2 ETC  Consists of 4 major protein complexes and 2 small shuttle carriers  Complexes – 1. NADH Dehydrogenase 2. Succina
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