Chapter 6 An Introduction To Metabolism

Chapter 6 An Introduction To Metabolism - Chapter 6 An...

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Chapter 6 An Introduction To Metabolism I. Metabolism, Energy and Life A. The chemistry of life is organized into metabolic pathways Metabolism = Totality of an organism's chemical processes - Property emerging from specific molecular interactions within the cell. - Concerned with managing cellular resources: material and energy. Metabolic reactions are organized into pathways that are orderly series of enzymatically controlled reactions. Metabolic pathways are generally of two types: Catabolic pathways = Metabolic pathways that release energy by breaking down complex molecules to simpler compounds (e.g., cellular respiration which degrades glucose to carbon dioxide and water; provides energy for cellular work). Anabolic pathways = Metabolic pathways that consume energy to build complicated molecules from simpler ones (e.g., photosynthesis which synthesizes glucose from CO 2 and H 2 O; any synthesis of a macromolecule from its monomers). Metabolic reactions may be coupled, so that energy released from a catabolic reaction can be used to drive an anabolic one. B. Organisms transform energy Energy = Capacity to do work Kinetic energy = Energy in the process of doing work (energy of motion). For example: - Heat (thermal energy) is kinetic energy expressed in random movement of molecules. - Light energy from the sun is kinetic energy which powers photosynthesis. Potential energy = Energy that matter possesses because of its location or arrangement (energy of position). For example: - In the earth's gravitational field, an object on a hill or water behind a dam have potential energy. - Chemical energy is potential energy stored in molecules because of the arrangement of nuclei and electrons in its atoms. Energy can be transformed from one form to another. For example: - Kinetic energy of sunlight can be transformed into the potential energy of chemical bonds during photosynthesis. - Potential energy in the chemical bonds of gasoline can be transformed into
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kinetic mechanical energy which pushes the pistons of an engine. C. The energy transformations of life are subject to two laws of thermodynamics Thermodynamics = Study of energy transformations First Law of Thermodynamics = Energy can be transferred and transformed, but it cannot be created or destroyed (energy of the universe is constant). Second Law of Thermodynamics = Every energy transfer or transformation makes the universe more disordered (every process increases the entropy of the universe). Entropy = Quantitative measure of disorder that is proportional to randomness (designated by the letter S). Closed system = Collection of matter under study which is isolated from its surroundings. Open system = System in which energy can be transferred between the system and its surroundings. The entropy of a system may decrease, but the entropy of the system plus its
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Chapter 6 An Introduction To Metabolism - Chapter 6 An...

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