Chapter 23 Metabolism and Nutrition Introduction Energy content in the human diet is measured in terms of heat calorie Measure of heat 1 calorie is the amount of heat required to raise temperature of one gram of water by one degree Celsius Kilocalorie Calorie actual unit of calorie used to measure human diet 1 kilocalorie is the amount of heat required to raise the temperature of one kilogram of water by one degree Celsius Overview of Metabolism and Nutrition Expected Learning Outcomes Define the terms metabolism catabolism and anabolism Identify the nutrients the body is able to use for fuel Compare and contrast endergonic and exergonic reactions Describe the process of phosphorylation Describe the hydrolysis of ATP and explain why this reaction in exergonic Explain what happens in an oxidation reduction reaction and how electrons are transferred between reactants including NADH and FADH2 Phases of Metabolism Metabolism sum of the body s chemical reactions that consists of a series of enzyme catalyzed reactions called metabolic pathways Harnessing energy in chemical bonds of molecules obtain from diet to make adenosine triphosphate ATP Converting one type of molecule into another Synthesizing macromolecules proteins lipids nucleic acids and polysaccharides Breaking down macromolecules into their monomers Metabolism is generally considered to consist of two phases Catabolism Breakdown of a large molecule into a smaller one Releases energy that can be harnessed Anabolism Synthesis of large molecules by combining smaller monomers Requires energy to proceed Nutrients That Undergo Catabolism Glucose Dietary carbohydrates and those stored by the body are typically degraded to the monosaccharide glucose Carried out by every cell in the body Preferred fuel for many cells brain and liver especially Fatty Acids Lipids mainly triglycerides are broken down into free fatty acids and glycerol Amino Acids Proteins are degraded to separate out the individual amino acids which can be converted to fuel or used to build new proteins Energy Requirements of Metabolic Reactions Chemical reactions are usually paired so that energy released from exergonic reactions can be harnessed to drive endergonic reactions Law of Conservation of Energy Energy cannot be created or destroyed it can only change forms Energy present before reaction in reactants must equal energy present after reaction in products or released as heat Energy Requirements of Metabolic Reactions Exergonic Reactions Release energy resulting in products with less energy than the original reactants possessed Most catabolic reactions Endergonic Reactions Require input of energy to proceed Products possess more energy than the reactants Most anabolic reactions ATP The Currency of Energy Adenosine Triphosphate ATP and Phosphorylation ATP Main form of energy currency in cells ATP is an inherently unstable molecule Phosphate groups repel one another strongly and this places strain on the molecule resulting in unstable bonds Bond between the 2nd and 3rd phosphate group is extremely unstable and releases a great deal of energy when broken Adenosine Triphosphate ATP and Phosphorylation Cells harness ATP energy by removing the 3rd phosphate group in a hydrolysis reaction ATP hydrolysis is highly exergonic but cell is only able to harness about 40 of the released energy to perform work The other 60 is lost as heat Most processes that burn fuel lose about 70 90 of their energy as heat Adenosine Triphosphate ATP and Phosphorylation Energy harnessed from ATP drives cellular processes in two ways Released energy can be used by the cell to directly fuel certain reactions such as muscle contractions Released energy can be used by the cell in a process called phosphorylation Phosphorylation Process where ATP donates a phosphate group to a reactant under direction of an enzyme Reactant becomes more reactive and favors the conversion of the reactant into the desired product Nutrients and ATP Generation Capability to use chemical energy in nutrients to drive synthesis of ATP is a result of the ability to transfer electrons from one reactant to another Oxidation Reduction Reactions When fuel is burned its electrons are transferred from one molecule to another Exergonic reaction that releases energy and heat Substance that loses electrons is oxidized Substance that gains electrons is reduced Flow of electrons from one molecule to another is then used to perform cellular work ATP synthesis Harnessing Electron Flow to Do Work Nutrients and ATP Generation Electron carriers molecules with high electron affinity Accept electrons that are removed from oxidation of nutrient molecules Many are peripheral and integral proteins found in mitochondrial membranes Nicotinamide adenine dinucleotide NAD and Flavin adenine dinucleotide FAD are found in the cytosol and mitochondrial matrix First electron carriers to accept electrons from nutrient molecules Nutrients and ATP Generation Reduced NAD and FAD eventually transfer their electrons to other electron carriers Generates an electromotive force linked to ATP synthesis Glucose Catabolism and ATP Synthesis Expected Learning Outcomes Explain the overall reaction for glucose catabolism Describe the processes of glycolysis formation of acetyl CoA and the citric acid cycle Discuss the process of the electron transport chain Discuss the process of chemiosmosis and its role in ATP production Give the energy yield of glucose catabolism Introduction to Glucose Catabolism Glucose catabolism Reactions that involve the breakdown of carbohydrates into the monosaccharide glucose Use the chemical energy in glucose s bonds to drive ATP synthesis glucose Two main components both generate ATP Glycolysis series of reactions that occur in cytosol to split Citric Acid Cycle Series of reactions that occur in the mitochondrial matrix that continues glucose s breakdown Introduction to Glucose Catabolism Oxidative phosphorylation series of oxidation reduction reactions that take place in the inner mitochondrial membrane Allows cells to use energy liberated by glucose catabolism Electron transport chain ETC involves the transfer of electrons during oxidative phosphorylation process Leads to ATP synthesis Introduction to Glucose Catabolism Figure 23 3 Overview of glucose catabolism and oxidative phosphorylation Overview of Glucose Catabolism ATP Synthesis A great deal of energy is contained within the bonds of a glucose molecule ATP can be synthesized