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Essential Idea • Cell respiration supplies energy for the functions of life. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Understanding • Cell respiration is the controlled release of energy from organic compounds to produce ATP. • ATP from cell respiration is immediately available as a source of energy in the cell. • Anaerobic cell respiration gives a small yield of ATP from glucose. • Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB Assessment Statement • Define cell respiration. • http://www.youtube.com/watch?v=00jbG_cf GuQ Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Define Respiration • Cell respiration is the controlled release of energy from organic compounds in cells to form ATP. • ATP or Adenosine triphosphates is the molecule which directly fuels the majority of biological reactions. – Everyday each person will hydrolyse (reduce) 1025 ATP molecules to ADP. – The ADP is reduced back to ATP using the free energy from the oxidation of organic molecules. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ATP = Life’s energy currency $$$$ • ATP (adenosine triphosphate) is the cell’s energy shuttle • ATP provides energy for cellular functions Chemical Energy and ATP ATP consists of: – adenine – ribose (a 5-carbon sugar) – 3 phosphate groups Adenine Ribose ATP Copyright Pearson Prentice Hall 3 Phosphate groups Chemical Energy and ATP Storing Energy ADP has two phosphate groups instead of three. A cell can store small amounts of energy by adding a phosphate group to ADP. ATP ADP + Adenosine Diphosphate (ADP) + Phosphate Partially charged battery Energy Energy Fully charged battery Copyright Pearson Prentice Hall Adenosine Triphosphate (ATP) Chemical Energy and ATP Releasing Energy Energy stored in ATP is released by breaking the chemical bond between the second and third phosphates. 2 Phosphate groups P ADP Copyright Pearson Prentice Hall • The bonds between the phosphate groups of ATP’s tail can be broken by hydrolysis • Energy is released from ATP when the terminal phosphate bond is broken P P P Adenosine triphosphate (ATP) H2O Pi + Inorganic phosphate P P + Adenosine diphosphate (ADP) Energy The Regeneration of ATP • ATP is a renewable resource that is regenerated by addition of a phosphate group to ADP • The energy to phosphorylate ADP comes from catabolic reactions in the cell • The chemical potential energy temporarily stored in ATP drives most cellular work ATP Energy from catabolism (energonic, energyyielding processes) ADP + P Energy for cellular work (endergonic, energyconsuming processes) i Chemical Energy Transfer Food to ATP • http://www.biologyinmotion.com/atp/index.html Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Pathways of cellular respiration and Production of ATP • There are several steps to the process of cellular respiration but the overall chemical equation is below: • C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy (ATP + heat) • Overall this equation states that glucose reacts with oxygen to form/ produce carbon dioxide and water • Note: Cellular respiration releases energy. It is therefore a exothermic (exergonic) reaction. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB Assesment Statement • State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Stages of Cellular Respiration: A Preview • Cellular respiration has three stages: 1. Glycolysis (breaks down glucose into two molecules of pyruvate) 2. The citric acid cycle/ Krebs Cycle (completes the breakdown of glucose) 3. Oxidative phosphorylation (accounts for most of the ATP synthesis) • The latter process generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions Glycolysis harvests energy by oxidizing glucose to pyruvate • Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate • Glycolysis occurs in the cytoplasm • Requires NO oxygen and so is considered an Anaerobic Reaction • The overall reaction for glycolysis is for every one molecule of glucose used: – 2 molecules of Pyruvate are formed – 2 net molecules of ATP are formed – 2 molecules of NADH are formed Glycolysis • Location: Cytoplasm • Process: Glycolysis • Substrate: Glucose • Products: 2 Pyruvate and a small amount of ATP • Glycolysis does not use oxygen. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis Animation • Watch Animation for more details: • http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapt er25/animation__how_glycolysis_works.html?is bn=0072507470&firstName=&MI=&lastName= &myEmail=&myStyle=&profEmail=&profStyle= &taEmail=&taStyle=&otherEmail=&otherStyle= Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB Assessment Statement • Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fermentation allows glycolysis to continue. Fermentation allows glycolysis to continue making ATP when oxygen is unavailable. • Fermentation is an anaerobic process. – occurs when oxygen is not available for cellular respiration – does not produce ATP There are two types of Fermentation/ anaerobic respiration 1. Lactic Acid Fermentation Glucose CYTOPLASM Pyruvate No O2 present Fermentation O2 present Cellular respiration MITOCHONDRION 2. Alcoholic Fermentation Ethanol or lactate Acetyl CoA Citric acid cycle Anaerobic Respiration • Anaerobic respiration is the oxidation of organic compounds without oxygen. • It is less efficient than aerobic respiration (with oxygen). • There are different types of anaerobic respiration. Here we will compare anaerobic respiration in yeast and humans. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Humans anaerobic respiration • Location: cytoplasm • Substrate: Glucose • Product: lactic acid (lactate) + ATP • Note: lactic anaerobic respiration supplements aerobic respiration in the production of ATP. Both aerobic and anaerobic respiration can take place in the human cell at the same time Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Humans anaerobic respiration Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings • Exercise and anaerobic respiration : • Human lactic anaerobic respiration is a process that supplements the production of ATP. • The lactic pathway is so inefficient that under normal circumstances it cannot produce enough energy to support human systems. • In describing the lactic pathway it is often suggested that sprinters 'do not breath during the 100m sprint' (they do, just watch any video) and they only produce ATP for running from the lactic pathway. • This is a mis-representation of a complex response to the demand for ATP. It is far better to consider that anaerobic respiration in humans supplements (adds to) the aerobic production of ATP. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Yeast anaerobic respiration: • Location: cytoplasm • Substrate: Glucose • Product: Ethanol + carbon dioxide + ATP • This is the end point for this fermentation reaction. Ethanol and CO2are both excreted with no further metabolism of the energy stored in the ethanol (very inefficient) • Note: The glucose molecule has been hydrolysed further than in human respiration. Some organisms are totally anaerobic others can switch between anaerobic and aerobic. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Yeast anaerobic respiration: Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Anaerobic respiration: • Fermentation respiration in yeast yields two useful products from a human perspective. • The carbon dioxide can be used in a variety industrial processes the best known of which is to raise bread. • Many Brewers of alcohol will bottle the CO2 for use in the 'carbonation' of other drink products. • The alcohol itself is of course the basis of many industries such as beer brewing. • In more recent time the use of fermentation products is being used as an alternative source of fuel such as is the case in fuel for automobiles. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings IB Assessment Statement • Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Aerobic Respiration • Location: Mitochondria • Substrate: Pyruvate • Products: ATP, Carbon dioxide, water and heat. • The production of ATP in the aerobic pathway is much greater than in either glycolysis or the anaerobic alternatives. The oxygen breathed in during ventilation is sent form the lung into the blood and then transported to the cell. The oxygen diffuses into the cell and then into the mitochondria for aerobic respiration Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Aerobic Respiration • This diagram is a summary of the complete aerobic pathway. • The by-product carbon dioxide is excreted and of course the heat produced is important in thermoregulation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Aerobic Respiration • (a) Glucose transported to the cell diffuses into the cytoplasm. Glucose is the initial substrate for respiration. • (b) Glycolysis in which glucose with six carbons is broken down into two Pyruvate each with 3 carbons. This yields a small amount of ATP. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Aerobic Respiration • (c) Anaerobic respiration in which lactic acid is produced, oxidation from glucose yields a small amount of ATP. • Remember that anaerobic respiration will occur at the same time as aerobic respiration to provided more energy. • (d) Aerobic respiration in which pyruvate is broken down, oxidised, further in the mitochondria where a lot of ATP is produced. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Aerobic Respiration (e) Oxygen is required for step (d)to be completed. This is transported to the cell on the haemoglobin found inside red blood cells. • (f) carbon dioxide is produced as waste from aerobic respiration it diffuses into the blood and is transported to the lungs where it is excreted in exhaled air. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings LE 9-6_1 Glycolysis Pyruvate Glucose Cytosol Mitochondrion ATP Substrate-level phosphorylation LE 9-6_2 Glycolysis Pyruvate Glucose Cytoplasm Krebs cycle Mitochondrion ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation LE 9-10 MITOCHONDRION CYTOPLASM NAD+ NADH + H+ Acetyl Co A Pyruvate Transport protein CO2 Coenzyme A LE 9-6_3 Electrons carried via NADH and FADH2 Electrons carried via NADH Glycolysis Pyruvate Glucose Cytosol Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Mitochondrion ATP ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation This is all occur in the folds of the inner membrane of the mitochondria 1 mitochondrion ATP matrix (area enclosed by inner membrane) and 6CO 2 energy 2 3 energy from glycolysis 6O and 2 inner membrane ATP and 6H O2 4 LE 9-16 Electron shuttles span membrane CYTOSOL 2 NADH Glycolysis Glucose 2 Pyruvate MITOCHONDRION 2 NADH or 2 FADH2 2 NADH 2 Acetyl CoA 6 NADH Citric acid cycle + 2 ATP + 2 ATP by substrate-level phosphorylation by substrate-level phosphorylation Maximum per glucose: About 36 or 38 ATP 2 FADH2 Oxidative phosphorylation: electron transport and chemiosmosis + about 32 or 34 ATP by oxidation phosphorylation, depending on which shuttle transports electrons form NADH in cytosol LE 9-18 Glucose CYTOSOL Pyruvate No O2 present Fermentation O2 present Cellular respiration MITOCHONDRION Ethanol or lactate Acetyl CoA Citric acid cycle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Practice Questions • Compare anaerobic and aerobic respiration Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Skills and Applications • Application: Use of anaerobic cell respiration in yeasts to produce ethanol and carbon dioxide in baking. • Application: Lactate production in humans when anaerobic respiration is used to maximize the power of muscle contractions. • Skill: Analysis of results from experiments involving measurement of respiration rates in germinating seeds or invertebrates using a respirometer. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings