Chapter 8 Outline - Summary Campbell Biology PDF

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Chapter 8: An Introduction to Metabolism 8.1 “An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics” Organization of the Chemistry of Life into Metabolic Pathways 

A metabolic process begins with a specific molecule, which then is altered in a series of defined steps, resulting in a certain product

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Each step of the pathway is catalyzed by a specific enzyme

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Mechanisms that regulate enzymes balance metabolic supply and demand, averting deficits or surpluses of important cellular molecules

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A major pathway of catabolism is cellular respiration, in which sugar glucose and other organic fuels are broken down in the presence of oxygen to carbon dioxide and water Forms of Energy

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Energy is the capacity to cause change

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Energy is important because some forms of energy can be used to do work—that is, to move matter against opposing forces, such as gravity and friction

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The forms of energy are kinetic, thermal (heat), potential, chemical energy The Laws of Energy Transformation

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The study of the energy transformations that occur in a collection of matter is called thermodynamics

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There are two laws of thermodynamics 8.2 “The free-energy change of a reactions tells us whether the reaction occurs spontaneously”

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The change in free energy can be calculated for any specific chemical reaction with the following formula: ∆G = ∆H - T∆S

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∆G = Change in free energy

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∆H= symbolizes the change in the system’s enthalpy

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∆S= the change in the system’s entropy

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T= the absolute temperature in Kelvin units (K) Free Energy and Metabolism

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Based on their free-energy changes, chemical reactions can be classified as exergonic (energy outward) or endergonic (energy inward)

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Exergonic reactions proceeds with a net release of free energy

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Endergonic reactions is one the absorbs free energy from its surroundings 8.3 “ATP powers cellular work by coupling exergonic reactions to endergonic reactions”

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A cell does three main kinds of work: o Mechanical work o Transport work o Chemical work

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A key feature in the way cells manage their energy resources to do this work is energy coupling

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ATP is responsible for mediating most energy coupling cells, and in most cases it acts as immediate source of energy that powers cellular work

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ATP+ H20 --> ADP + ℗1 How ATP Performs Work

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When ATP is hydrolyzed in a test tube, the release of free energy merely heats the surrounding water

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With the help of specific enzymes, the cell is able to couple the energy of ATP hydrolysis directly to endergonic processes by transferring a phosphate group from ATP to some other molecule The Regeneration of ATP

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ATP is a renewable resource that can be regenerated by the addition of phosphate to ADP

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The free energy required to phosphorylate ADP comes from exergonic breakdown reactions in the cell 8.4 “Enzymes speed up metabolic reactions by lowering energy barriers”

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A catalyst is a chemical agent that speeds up a reaction without being consumed by the reaction

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An enzyme is a catalytic protein

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Enzymes speed up metabolic processes by lowering activation energy Substrate Specificity of Enzymes

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The reactant an enzyme acts on is referred to as the enzyme’s substrate

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The enzyme binds to its substrate forming in enzyme-substrate complex Effects of Local Conditions on Enzyme Activity

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The activity of an enzyme—how efficiently it runs—is affected by general environmental factors, such as temperature and pH 8.5 “Regulation of enzyme activity helps control metabolism”

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Allosteric regulation is the term used to describe any case which a proteins functions at one site is affected by the binding of a regulatory molecule to a separate site Specific Localization of Enzymes Within the Cell

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Structures within the cell help bring order to a metabolic pathways...