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Chapter 6 notes

by: Megan Smith

Chapter 6 notes Biol 1103k

Megan Smith
GPA 3.6

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this is notes of chapter 6 from the biology text book
Introductory biology I
David blaustein
Class Notes
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This 5 page Class Notes was uploaded by Megan Smith on Sunday February 14, 2016. The Class Notes belongs to Biol 1103k at Georgia State University taught by David blaustein in Summer 2015. Since its upload, it has received 26 views. For similar materials see Introductory biology I in Biology at Georgia State University.


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Date Created: 02/14/16
Date CHAPTER 6 – ENERGY FLOW IN THE LIFE OF A CELL 1. WHAT IS ENERGY i. Energy • The capacity to do work ii. work • the transfer of energy to an object, causing the object to move iii. Chemical energy • Energy available in the bonds of molecules iv. There are two types of energy : a. potential energy i. Stored energy, includes the chemical energy available in biological molecules and other molecules b. kinetic energy i. the energy of movement • Under the right conditions, kinetic energy can be transformed into potential energy, and vice versa B. The laws of thermodynamics describe the basic properties of energy i. the law of thermodynamics • describes the quantity ( the total amount) and the quality ( the usefulness) of energy. ii. the first law of thermodynamics • States that energy can neither be cre ated nor destroyed by ordinary processes iii. (hypothetical) - Closed system • Energy can neither lea ve nor enter • the total amount of energy before and after any process will be unchanged iv. law of conservation of energy • often the name for the first law of thermodynamic v. Energy can be converted from one form to another vi. Second law of thermodynamic • When energy is converted from one form to another, the amount of useful energy decreases. • No energy conversion process is 100% efficient in using energy to achieve a specific outcome vii. Entropy • Tendency towards loss of complexity, orderliness, and useful energy • The concurrent increase in randomness, disorder, and less useful energy 2. HOW IS ENERGY TRANSFO RMED DURING CHEMICAL REACTIONS? i. Chemical reaction • A process that forms or breaks the chemical bonds that hold atoms together • Convert one set of chemical substances, the reactants, into another set, the products. ii. Exergonic • Energy out • The reaction releases energy; that is, if the starting reactants contai n more energy than the end products iii. Endergonic • Energy in • Requires a net input of energy; that is, if the products contain more en ergy than the reactants • Require a net influx of energy from an outside source B. Exergonic reactions release energy i. The total energy in the reactant molecules is much higher than in the product molecules C. Endergonic reactions require a new input of energy i. The reactants contain less energy than the products do D. All chemical reactions require activation energy to begin i. Activation energy • The energy “push” in a chemical reaction • Shells of negatively charged electrons surround all atom • Activation energy is the energy that is required to overcome the repulsive electrical forces between the electron shell so that they can move close enough together to react • Can be provided by the kinetic energy of moving molecules 2 3. HOW IS ENERGY TRANSP ROTED WITHIN A SHELL i. Energy carrier molecules • High-energy molecules that are synthesized at the site of an exergonic reaction, where they capture some of the released energy B. ATP and electron carriers transport energy within cells i. Adenosine triphosphate (ATP) • Many exergonic reactions in cells, such as breaking down sugars and fats , produce ATP • the most common energy carrier molecule in the body • a nucleotide composed of the nitrogen containing base , adenine, the sugar ribose, and three phosphate groups • sometimes call the “Energy currency” of cells • diffuses throughout the cell, carrying energy to sites where endergonic reactions occur • there is energy is liberated as it is broken down, regenerating ADP and Pi • not a long term energy -storage molecule ii. adenosine diphosphate (ADP) • inorganic phosphate • requires an input of energy, ATP synthesis is endergonic iii. electron carriers • captures energetic electrons, along with hydrogen ions • loaded electron carriers donate their high -energy electrons to other molecules which a re often involved in pathways that generate ATP C. Coupled reactions link exergonic with endergonic reactions i. Coupled reaction • An exergonic reaction provides the energy needed to drive an endergonic reaction using ATP or electron carriers as intermediaries • The energy released by exergonic reactions must always exceed the energy needed to drive the endergonic reaction • Energy is transferred from place to place by energy carrier molecules such as ATP 4. HOW DO ENZYMES PROMO STE BIOCHEMICAL REAC TONS i. Catalysts • Molecules that speed up the rate of reaction without themselve s being used up or permanently altered • All catalysts share three important properties 3 a. Speed up the r eactions by lowering the activation energy required for the reaction to begin b. Can speed up both exergonic and endergonic reaction, but they cannot make an endergonic reaction occur spontaneously c. Are not consumed or permanently changed by the reactions they promote B. Enzymes are biological catalysts i. Enzymes • Called employ highly specified biological catalysts called enzymes • Nearly all of which are proteins C. The structure of enzymes allows them to catalyze specific reactions i. The function of an enzyme is determined by its structure ii. Active site • Reactants molecules can enter this site iii. Substrates • Reactant molecules D. Enzymes, like all catalysts lower activation energy 5. HOW ARE NEZYMES REGULATE D i. Metabolism • The sum of all its chemical reactions ii. Metabolic pathway • Many chemical reactions, such as those that break down glucose into CO2 and water, are lined in sequences called metabolic pathways B. Cells regulate metabolic pathways by controlling enzyme synthesis and activity i. The rate of a reaction will depend on how many substrate molecules diffuse into the active sites of enzyme molecules in a given time period ii. Increasing the concentration of the substrate or enzyme (or both) will increase the reaction rate C. Genes that code the enzymes may be turned off or on D. Some enzymes are synthesized in inactive forms i. Some enzymes re synthesized in an inactive form that are activated under the conditions found where the enzyme is needed. E. Enzyme activity may be controlled by competitive or non competitive inhibition i. Competitive inhibition 4 • Substance that is not the enzyme’s normal substrate can also bind to the active site of the enzyme, competing with the substrate for the active site ii. Noncompetitive inhibition • A molecule binds to a site on the enzyme that is distinct fr om the active site F. Some enzymes are controlled by allosteric regulation i. Allosteric regulation • Activate or inhibit enzymes • The number of enzyme molecules being activated (or inhibited) is proportional to the numbers of activator (or inhibitor) molecules that are present at any given time ii. Feedback inhibition • Causes a metabolic pathway to stop producing tis end product when the product concentration reaches an optimal level G. Poisons, drugs and environmental conditions influence enzyme activity i. Poisons and drugs acting on enzymes usually inhibit them, either competitively or noncompetitively H. Some poisons and drugs are competitive or noncompetitive inhibitors of enzymes i. Competitive inhibitors of enzymes permanently block the active site of the enzyme acetylcholinesterase , which breaks down acetylcholine I. The activity of enzymes is influenced by their environment i. Denatured • The enzyme loses the exact three-dimensional structure required for it to function properly ii. Temperature effects the rate of enzyme-catalyzed reactions • Slowed by lower temperature • Accelerated by moderately higher temperatures 5


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