Session 6 (Energy, Enzymes and Metabolism)

Session 6 (Energy, Enzymes and Metabolism) - MCB 181 Study...

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Unformatted text preview: MCB 181 Study Session 6 (Energy, Enzymes and Metabolism) Learning Goals for Study Session 6 (Energy, Enzymes and Metabolism) Define energy and briefly describe its role in living cells. Be able to describe the first two laws of thermodynamics and how they relate to life on Earth. Define the terms free energy, enthalpy, and entropy. Briefly describe an equation that relates these three terms. Be able to relate changes in free energy to endergonic and exergonic reactions in cells. Distinguish between energy requiring and energy yielding reactions in cells. Briefly describe the roles of NADPH, NADH, and ATP in meeting the energy needs of cells. Be able to define the term enzyme, describe why enzymes are needed and what they do in cells. Define the terms cofactor, prosthetic group, coenzyme, competitive and noncompetitive inhibitors and allosteric enzymes. Briefly describe what is meant by anabolic and catabolic metabolism, and regulation of a metabolic pathway. All living organisms, need a constant supply of energy to stay alive! In this study session we will consider: (1) what is meant by the term energy (2) the laws that govern energy transfers (3) the difference between energy requiring and energy yielding reactions (4) some molecules that cells employ to store and transfer energy (5) the function of enzymes in cell biochemistry, and (6) what is meant by the term metabolism What is energy? Energy is an elusive concept. It is defined by what it does rather than by what it is. Energy is the capacity to do work. Work is anything that requires energy. Work moves things in directions in which they would not move if left alone. In our physical world, work is lifting, moving, heating, cooling, studying, writing, and so forth. In living cells, work is: Synthesis of biochemicals like proteins and nucleic acids Active transport of molecules through cell membranes Moving chromosomes during cell division Growth, development, reproduction virtually everything a cell does requires energy! All energy exchanges are governed by laws of thermodynamics. First Law of Thermodynamics states that energy can be changed from one form to another, but cannot be created or destroyed. Forms of energy include thermal (heat energy), radiant (light), mechanical, electrical (flow of charged particles) and chemical (arrangement of covalent bonds), but all forms of energy fall into two broad categories. Kinetic energy is released by objects in motion and being used to do work. Potential energy is stored because of location (e.g. object on top of a hill) or arrangement of, for example, chemical bonds in molecules. The First Law of Thermodynamics is illustrated below. The water flowing down the river possesses kinetic energy that can be stored (potential energy) behind the dam and/or used to drive a turbine for the generation of electrical energy. In turn, the electrical energy can be stored in a battery for later use in, for example, a cell phone or used directly to heat a filament in a bulb to produce light. filament in a bulb to produce light....
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This note was uploaded on 03/24/2010 for the course MCB 181 taught by Professor Jorstad during the Spring '07 term at University of Arizona- Tucson.

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Session 6 (Energy, Enzymes and Metabolism) - MCB 181 Study...

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