Cellular Respiration.Chapter 9
Cellular Respiration.Chapter 9 BIOl 1020-003
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This 6 page Class Notes was uploaded by Crystal Boutwell on Friday October 2, 2015. The Class Notes belongs to BIOl 1020-003 at Auburn University taught by Dr. Zhong in Fall 2015. Since its upload, it has received 38 views. For similar materials see Principles of Biology in Biology at Auburn University.
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Date Created: 10/02/15
CHAPTER 92 CELLULAR RESPIRATION AND FERMENTATION Compiled by Crystal Boutwell The energy stored in the organic molecules of food comes from the sun and exits as heat Photosynthesis generates oxygen and organic molecules that are used by the mitochondria as fuel for cellular respiration Respiration breaks fuel down generating ATP Light X Energy Absorbed by Photosynthesis plants in plants C02 H20 which enters the ecosystem Cellular Respiration in mitochondria of animals ATP Heat Energy Catabolic pathways oxidize organic fuels in order to produce energy A Catabolic pathways stored energy by complex molecules B Compounds that can participate in exergonic reactions can act as fuels i Fermentation breaking down sugars or other fuels without using oxygen ii Aerobic respiration breaking down and consumption of an organic fuel This is the most effective catabolic pathway C Cellular Respiration organic compounds oxygen 9 carbon dioxide water energy i Carbohydrates fats and protein molecules from food can all be processed and consumed as a fat However in the book we look at the example of glucose a sugar ii Cellular Respiration by breaking down glucose Organic Molecules 02 ATP 2 Exergonic 3 Spontaneous D OxidationReduction electron transfers i Oxidation loss of electrons ii Reduction addition of electrons 1 Adding electrons reduces the charge ofthe atom iii Na Cl 9 Na Cl39 Na becomes oxidized and Cl becomes reduced iv C6H1206 602 9 6C02 6HzO ENERGY Glucose becomes oxidized and Oxygen becomes reduced v Electrons lose potential energy as molecules get less complex Hence carbon dioxide has less potential energy than glucose Glucose is broken down in a series of steps i Hydrogen atoms are passed from glucose to oxygen through an electron carrier a coenzyme called NAD ii Dehydrogenase enzymes remove a pair of H atoms 2 electrons and 2 protons from glucose thereby oxidizing it It delivers 2 electrons and 1 proton to NAD making NADH The other proton is released into the solution iii NADH represents stored energy It is used to make ATP Electron Transport Chain ETC a number of mostly protein molecules built into the inner membrane of the mitochondria of Eukaryotic cells Electrons from glucose are transported here by NADH to one end of the chain Oxygen picks them up and forms water i Movement of electrons glucose 9 NADH 9 ETC 9 oxygen Steps of cellular respiration i Glycolysis Occurs in the cytosol It breaks glucose into two pyruvates which will enter the mitochondria and be oxidized to form Acetyl CoA ii Citric Acid Krebs cycle releases C02 and finishes the breakdown of the 6C glucose molecule iii Oxidative Phosphorylation the ETC accepts electrons from NADH to form water and ATP Glycolysis the Oxidation of glucose to pyruvate A B C D E F G 3 Kill 3 Glycolysis means quotsugar splitting Glucose is a 6Carbon sugar 6C which through glycolysis splits into 2 3C sugars The 2 3C sugars are oxidized and their remaining atoms are rearranged to form 2 molecules of pyruvate Pyruvate is an ionized form of pyruvic acid Net Energy yield 2 ATP and 2 NADH ATP 3 phosphate groups ADP 2 phosphate groups No carbon released as Carbon Dioxide Occurs whether or not there is Oxygen present P XZ 4ADP 4ATP 39 gtX OP 2 NAD 2 NADH Pyruvate must be oxidized into Acetyl CoA and then it goes through the Citric Acid Cyle Krebs cycle to complete the degredation of the organic molecule A Pyruvate enters the mitochondria B There it is converted into Acetyl CoA iThis is carried out by a multienzyme complex that catalyzes 3 Goo ych 3m reactions AD 1 Pyruvate s carboxyl group is removed and given off as C02 1 239 The remaining 2C fragment is oxidized forming Acetate q 3 Coenzyme A CoA A sulfur containing compound AC39Nl39l39CC39A from Vitamin B attaches to acetate to form Acetyl CoA Smnun A C Citric Acid Cycle Krebs cycle This is a metabolic furnace that oxidizes organic fuel from MD pyruvate 1 Produces 2 C02 molecules per turn 1 2 1 ATP generated per turn 3 3quot 3 Electrons are transferred to NAD and FAD 50 d 4 There are two pyruvates so there are two turns Everything doubles 000 ii Process Giffz39jj l 06009 1 2 Cs enter as Acetyl CoA 9 produces citrate 2 Electron loss to NAD Loses C02 3 C02 lost NADH produced mp L 4 CoA kicked out Generation of ATP 5 Two H go to FAD 9 FADH2 NAD39 CC 6 NADH produced IV Oxidative Phosphorylation involves chemiosmosis and electron transport to produce ATP A Electron Transport Chain ETP a collection of molecules embedded in the inner membrane of the mitochondria mostly proteins i Electrons acquired from glucose by NAD during glycolysis and the krebs cycle are transferred from NADH to the 1St molecule of the ETC in complex I ii FADH2 adds electrons B ATP synthase the enzyme that makes ATP from ADP and inorganic phosphates C Chemiosmosis the process in which energy is stored in the form of Hydrogen ion gradient across a membrane and is used to drive cellular work such as ATP synthesis D H moves into one part of ATPS and causes the rotor to spin catalyzing ATP from ADP Kind of like a water wheel 65 ATP synthase complex electron transport system V Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen A Most of the ATP generated by cellular respiration is due to oxidative phosphorylation Without Oxygen oxidative phosphorylation ceases B Anearobic respiration uses and ETC i Takes place in certain prokaryotic organisms that live without oxygen ii Other less electronegative substances serve as final electron acceptors of the ETC C Fermentation does not use ETC i Harvests chemical energy without oxygen or ETC ii Glycolysis oxidizes without oxygen iii Fermentation is an extension of glycolysis 1 Recycles NAD iv Types of Fermentation 1 Alcohol Fermentation pyruvate 9 ethanol a Release C02 from pyruvate which converts to 2C acetaldehyde b Acetaldehyde reduced by NADH to ethanol 2 Lactic Acid Fermentation pyruvate 9 lactate a No COZ b Occurs in human muscle cells during strenuous exercise c Excess lactate is carried by blood to liver where it is converted back to pyruvate by liver cells v Fermentation vs Anaerobic vs Aerobic 1 Similarities a All 3 use glycolysis b Nad is the oxidizing agent 2 Differences a How they oxidize NADH back to NAD i Fermentation the final electron acceptor is an organic molecule ii Cellular respiration electron is carried by NADH transferred to ETC b Amount of ATP produced i Fermentation 2 ii Cellular respiration 3032 vi Obligate anaerobes organisms which carry out only fermentation or anaerobic respiration They cannot survive in the presence of oxygen vii Facultative anaerobic yeasts and bacteria can make enough ATP to survive using either fermentation or respiration Muscle cells in humans 1 Pyruvate is a fork in the road 2 To make the same amount of ATP a facultative anaerobe has to consumer sugar at a much faster rate when fermenting than when respiring VI Glycolysis and the Citric Acid Cycle connect to many other metabolic Pathways A Free glucose molecules are not common in the diets of most animals and humans We obtain most of our calories in the form of fats proteins sucrose and starch B Glycolysis can accept a wide range of carbohydrates C Deamination a process of removing amino groups from amino acids before they can feed into glycolysis The nitrogenous refuse is excreted from animals as ammonia urea D Beta oxidation breaks fatty acids down to 2C fragments which enter the citric acid cycle as acetyl CoA They make excellent fuels Proteins Carbohydrates Amino Acids Fatty Acids Suga r5 Glycerol GLYCOLYSIS Glucose Glyceraldehyde 3P Pyruvate Acetyl CoA Krebs cycle Oxidative Phosphorylation E Biosynthesis anabolic i Not all organic molecules of food are destined to be oxidized as fuel to make ATP 1 Amino acids make proteins 2 Intermediate compounds formed can be diverted into anabolic pathways VII Feedback mechanisms regulate cellular Respiration A Think supply and demand B If there is excess of a product the pathway shuts off anabolic C Feeback inhibition the end product of the anabolic pathway inhibits the enzyme that catalyzes an early step of the pathway Prevents the needless diversion of key metabolic intermediates from uses that are more urgent D When there is plenty of ATP respiration slows down When there is a demand of ATP respiration speeds up E Phosphofructokinase an important switch The enzyme that catalyzes step 3 of glycolysis Commits the substrate irreversibly to the glycolytic pathway i Inhibited by ATP and stimulated by AMP remember ATP has 3 phosphate groups and the most energy AMP has only one phosphate group So the more ATP the slower the reaction but the more you need ATP the faster the reaction ii Also sensitive to citrate the first part of the Citric Acid Cycle As citrate accumulates input of acetyl decreases If citrate consumption increases glycolysis accelerates F Metabolic balance is augmented by the control of enzymes that catalyze other key steps of Inhibits glycolysis and Citric Acid Cycle Glucose G LYCOLYSIS Stimulates Fructose 6Phosphate Phosphofructokinase Fructose 1 6biphosphate Pyruvate Acetyl CoA Citrate Inhibits Oxidative Phosphorylation
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