Cellular Respiration How We Obtain Chemical Energy from Food. Learner Outcomes: 1. I can explain the relationship between cellular respiration and photosynthesis. 2. I can write the overall equation for cellular respiration and identify the products and reactants. 3. I can describe the three stages of cellular respiration. Energy Flow and Chemical Cycling in the Biosphere Fuel molecules in food represent solar energy. Energy stored in food can be traced back to the sun. Animals depend on plants to convert solar energy to chemical energy. This chemical energy is in the form of sugars and other organic molecules. Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings Chemical Cycling between Photosynthesis and Cellular Respiration The ingredients for photosynthesis are carbon dioxide and water. CO2 is obtained from the air by a plant’s leaves. H2O is obtained from the damp soil by a plant’s roots. Chloroplasts rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules. Oxygen gas is a by-product of photosynthesis. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings Chemical Cycling between Photosynthesis and Cellular Respiration Both plants and animals perform cellular respiration. Cellular respiration harvests energy from organic molecules. Occurs in mitochondria. The waste products of cellular respiration, CO2 and H2O, are used in photosynthesis. Cellular Respiration ATP-producing process in which the ultimate electron acceptor is Oxygen Is an exergonic process (releases energy) The Relationship between Cellular Respiration and Breathing Cellular respiration requires a cell to exchange gases with its surroundings. Breathing exchanges these gases between the blood and outside air. Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings Cellular Respiration Carbohydrates, Proteins, and fats can all be broken as fuel, but cellular respiration most often described as: C6H12O6 + 6O2 6CO2 + 6H2O + Energy (ATP + Heat) Process transfers energy stored in food molecules to ATP The Process of Cellular Respiration: Process that releases energy by breaking down food in presence of oxygen. three main metabolic stages: 1. Glycolysis 2. Krebs Cycle 3. Electron Transport Chain and Oxidative Phosphorylation Overview continued Takes place in the cytoplasm of the cell and the mitochondria. Equation: 6O2 + C6H12O6 6CO2 + 6H20 + energy How is this equation related to the photosynthesis equation? Glycolysis The process in which one molecule of glucose is broken down in half. Takes place in cytoplasm. This produces two molecules of pyruvic acid, a 3-carbon compound. Glycolysis continued The cell has to contribute 2 ATP molecules at the beginning of glycolysis to get things going. 4 ATP molecules have been produced at the end of glycolysis for a net gain of 2 ATP. Although the energy yield is small, the process is so fast that cells can produce thousands of ATP molecules in milliseconds. Does not require oxygen. Aerobic respiration At the end of glycolysis, about 90 percent of the chemical energy that was available in glucose is still unused (pyruvic acid) Cell turns to oxygen for final steps of cellular respiration. Krebs Cycle Electron Transport Chain Krebs Cycle Named after Hans Krebs During this cycle, pyruvic acid is broken down into carbon dioxide in a series of energyextracting reactions. Takes place in mitochondria. Electron Transport Chain The Krebs Cycle spins round and round to produce high-energy electrons, which are then passed to the electron transport chain. The ETC uses these high-energy electrons to convert ADP into ATP. Takes place in cristae: folds in mitochondria. The Totals: How much energy does cellular respiration yield from a single molecule of glucose? 2 molecules of ATP from glycolysis 34 molecules of ATP from Krebs Cycle and Electron transport chain. Total ATP from one molecule of glucose: 36 ATP. Totals Continued 18 times as much ATP can be generated from glucose in the presence of oxygen then without. How efficient is cellular respiration? 36 ATP represent about 38 % of the total energy of glucose. What happened to other 62%? Review of Cellular Respiration Process that releases energy by breaking down food in presence of oxygen. Three processes make up cellular respriation: Glycolysis Krebs Cycle Electron Transport Chain Anaerobic respiration: No Oxygen Fermentation: releases energy from food molecules in the absence of oxygen. Two main types: Alcoholic fermentation Lactic acid fermentation Fermentation Alcoholic Fermentation Occurs in plant cells and some microorganisms. Alcohol is produced as a by-product of ATP production. Important in bread, cheese, wine industry. Lactic Acid Fermentation Occurs in animal cells when oxygen is not present. Lactic acid is produced as a byproduct of producing ATP without oxygen. Energy and Exercise To obtain energy during exercise, the body uses ATP already in muscles and new ATP made by lactic acid fermentation and cellular respiration. The Effect of Exercise on Physical Activity As the activity level increases, so does the rate of cellular respiration (and thus your breathing rate). Your body must take in more oxygen to supply enough ATP to cells for activity. Quick energy: What happens when your body needs energy quickly? Cells can provide enough energy from ATP for a few seconds. After this, ATP is produced by lactic acid fermentation; enough for about 90 seconds. Lactic acid builds up in you and this is why muscles get sore!! Long-Term Energy: Sustained energy over a long period of time. For exercise over 90 seconds, cellular respiration is the only way to generate a continuing supply of ATP. This is why our breathing rate increases during exercise! Energy is stored in the body as the carbohydrate glycogen: 15-20 minutes. After that, body begins to break down other molecules, such as fat.