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CH8_outline - 1 2 3 CHAPTER 8 Overview The Energy of Life...

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1 CHAPTER 8 Overview: The Energy of Life • The living cell is a miniature chemical factory where thousands of reactions occur • The cell extracts energy and applies energy to perform work • Some organisms even convert energy to light, as in bioluminescence An organism’s metabolism: subject to the laws of thermodynamics • Metabolism is the totality of an organism’s chemical reactions • Metabolism is an emergent property of life that arises from interactions between molecules within the cell Organization of the Chemistry of Life into Metabolic Pathways • A metabolic pathway begins with a specific molecule and ends with a product • Each step is catalyzed by a specific enzyme • Catabolic pathways release energy by breaking down complex molecules into simpler compounds • Cellular respiration, the breakdown of glucose in the presence of oxygen, is an example of a pathway of catabolism • Anabolic pathways consume energy to build complex molecules from simpler ones • The synthesis of protein from amino acids is an example of anabolism • Bioenergetics is the study of how organisms manage their energy resources Forms of Energy • Energy is the capacity to cause change • Energy exists in various forms, some of which can perform work Forms of Energy • Kinetic energy is energy associated with motion • Heat (thermal energy) is kinetic energy associated with 1 2 3 4 5 6 7 8
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2 • Heat (thermal energy) is kinetic energy associated with random movement of atoms or molecules • Potential energy is energy that matter possesses because of its location or structure • Chemical energy is potential energy available for release in a chemical reaction • Energy can be converted from one form to another The Laws of Energy Transformation THERMODYNAMICS • A closed system, such as that approximated by liquid in a thermos, is isolated from its surroundings • In an open system, energy and matter can be transferred between the system and its surroundings • Organisms are open systems The First Law of Thermodynamics • According to the first law of thermodynamics, the energy of the universe is constant: Energy can be transferred and transformed, but it cannot be created or destroyed • The first law is also called the principle of conservation of energy The Second Law of Thermodynamics • During every energy transfer or transformation, some energy is UNusable, and is often lost as heat • According to the second law of thermodynamics: Every energy transfer or transformation increases the entropy (disorder) of the universe • Living cells unavoidably convert organized forms of energy to heat • Spontaneous processes occur without energy input; they can happen quickly or slowly • For a process to occur without energy input, it must increase the entropy of the universe Biological Order and Disorder • Cells create ordered structures from less ordered materials 9 10 11 12 13
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3 • Cells create ordered structures from less ordered materials
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