Chapter 6 - CHAPTER 6 - AN INTRODUCTION TO METABOLISM A....

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CHAPTER 6 - AN INTRODUCTION TO METABOLISM A. Metabolism, Energy, and Life 1. The chemistry of life is organized into metabolic pathways The totality of an organism’s chemical reactions is called metabolism . A cell’s metabolism is an elaborate road map of the chemical reactions in that cell. Metabolic pathways alter molecules in a series of steps. Enzymes selectively accelerate each step. The activity of enzymes is regulated to maintain an appropriate balance of supply and demand. Catabolic pathways release energy by breaking down complex molecules to simpler compounds. This energy is stored in organic molecules until it needs to do work in the cell. Anabolic pathways consume energy to build complicated molecules from simpler compounds. The energy released by catabolic pathways is used to drive anabolic pathways. Energy is fundamental to all metabolic processes, and therefore to understanding how the living cell works. The principles that govern energy resources in chemistry, physics, and engineering also apply to bioenergetics , the study of how organisms manage their energy resources. 2. Organisms transform energy Energy is the capacity to do work - to move matter against opposing forces. Energy is also used to rearrange matter. Kinetic energy is the energy of motion. Objects in motion, photons, and heat are examples. Potential energy is the energy that matter possesses because of its location or structure. Chemical energy is a form of potential energy in molecules because of the arrangement of atoms. Energy can be converted from one form to another. For example, as a boy climbs a ladder to the top of the slide he is converting his kinetic energy to potential energy. As he slides down, the potential energy is converted back to kinetic energy. It was the potential energy in the food he had eaten earlier that provided the energy that permitted him to climb up initially. Cellular respiration and other catabolic pathways unleash energy stored in sugar and other complex molecules.
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This energy is available for cellular work. The chemical energy stored on these organic molecules was derived primarily from light energy by plants during photosynthesis. A central property of living organisms is the ability to transform energy. 3. The energy transformations of life are subject to two laws of thermodynamics Thermodynamics is the study of energy transformations. In this field, the term system indicates the matter under study and the surroundings are everything outside the system. A closed system , like liquid in a thermos, is isolated from its surroundings. In an
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This note was uploaded on 12/14/2009 for the course BIOCHEM bIO taught by Professor Professor during the Spring '09 term at École Normale Supérieure.

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Chapter 6 - CHAPTER 6 - AN INTRODUCTION TO METABOLISM A....

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