BIOL 201 Chapter 6 notes
BIOL 201 Chapter 6 notes BIOL 201-015
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This 4 page Class Notes was uploaded by Kayla Wisotzkey on Monday September 26, 2016. The Class Notes belongs to BIOL 201-015 at Towson University taught by Cheryl D. Warren in Fall 2016. Since its upload, it has received 31 views. For similar materials see Intro to Cell Biol & Genetics in Biology at Towson University.
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Date Created: 09/26/16
Kayla Wisotzkey Chapter 6 Thermodynamics: the branch of chemistry concerned with energy changes energy: the capacity to do work kinetic energy: the energy of motion… moving objects perform work by causing other matter to move potential energy: stored energy… the capacity to move the sun provides energy to all living things: a) energy absorbed from sunlight is used to combine small molecules into more complex ones b) the sun converts carbon from an inorganic to an organic form c) energy from sunlight is stored as potential energy oxidation: when a molecule or atom loses an electron reduction: when a molecule or atom gains an electron (higher level of energy) The Laws of Thermodynamics 1 Law of Thermodynamics: energy cannot be created or destroyed; it can only change from one form to another chemical potential energy that is stored in some molecules can be shifted to other molecules and stored in different chemical bonds… some of the energy dissipates into the environment as heat 2 Law of Thermodynamics: some energy is lost as disorder in the universe entropy: all of the disorder in the universe; constantly increasing Free energy: the energy available to do work in any system; the amount of energy available to break and form other chemical bonds the change in free energy allows us to predict whether a chemical reaction is spontaneous or not change in free energy=energy of productsreactants endergonic reaction: the products have more free energy than the reactants… the reaction is not spontaneous because they need an input of energy exergonic reaction: the products have less free energy than the reactants… the reaction is spontaneous an exergonic reaction has an equilibrium favoring the products, and an endergonic reaction has an equilibrium favoring the reactants chemical equilibrium: the forward and reverse reactions proceed at the same rate activation energy: the extra energy needed to destabilize existing chemical bonds and start a chemical reaction to increase the rate of reactions: a. Increase the energy of reacting molecules b. Lower activation energy catalysts: substances that influence chemical bonds to lower the activation needed to start a reaction ATP: the currency that cells use for energy transactions it powers almost every energy requiring process in cells… makes sugars, supplies energy for chemical reactions, transports substances across membranes it is not suitable for long term energy storage structure of ATP: 1. Ribose: 5 carbon sugar that serves as the framework to which the other two subunits are attached 2. Adenine: organic molecule composed of 2 carbonnitrogen rings… weak base 3. Three phosphates How ATP stores energy: the phosphate groups are highly negative charged and repel each other, making the covalent bonds connecting the phosphates unstable when a bond breaks, ATP becomes ADP and a phosphate, and 7.3 kcal/ mole of energy is released cells use ATP to drive endergonic reactions (which don’t proceed spontaneously because their products possess more free energy than their reactants) ATP can provide most of the energy a cell needs: helps generate force in muscles, creates concentration gradients of important ions ATP cycles continuously Enzymes: mostly proteins that act as catalysts to speed up chemical reactions enzymes lower the activation rate of reactions the shape of an enzyme allows it to stabilize an association between substrates (the molecules that will undergo a reaction) by bringing the two substrates together in the correct orientation, which lowers the activation energy required for new bonds to form The enzyme is not changed or consumed in the reaction, so it can be used over and over metabolism: the collection of all chemical reactions By facilitating particular chemical reactions, the enzymes in a cell determine the course of metabolism in that cell active sites: the pockets or clefts on the enzyme that the substrates bind to, forming an enzymesubstrate complex The binding of a substrate makes the enzyme adjust its shape so it fits better with that substrate… this may facilitate the binding of other substrates to the enzyme The steps of catalysis: 1) The substrate (sucrose) consists of glucose and fructose bonded together 2) The substrate binds to the active site of the enzyme, forming an enzymesubstrate complex 3) The binding of the substrate and enzyme places stress on the glucosefructose bond, and the bond breaks 4) Products are released; the enzyme can bond to other substrates Multienzyme complexes: the assemblies of several enzymes catalyzing different steps in a sequence of reactions… speeds the overall process up Advantages of multienzyme complexes: 1) The product of one reaction can be delivered to the next enzyme without releasing it to diffuse away 2) Unwanted side reactions are prevented because the reacting substrate doesn’t leave the complex while it goes through the series of reactions 3) All of the reactions that take place within the multienzyme complex can be controlled as a unit Nonprotein enzymes: enzymes that are not proteins RNA catalysts: “ribosomes,” accelerate the rate of biochemical reactions but aren’t proteins a) Intramolecular catalysis: when the ribosomes have a folded structure and catalyze reactions on themselves b) Intermolecular catalysis: when the ribosomes act on other molecules without being changed themselves Temperature, pH, and the binding of regulatory molecules affect the enzymes ability to catalyze a reaction Temperature: increasing the temp. of an uncatalyzed reaction increases its rate because heat increases molecular movement the rate of an enzymecatalyzed reaction increases with temperature up to the optimum temperature… at extremely high temperatures, the enzyme denatures pH: ionic interactions are sensitive to the H ion concentration of the fluid in which the enzyme is dissolved some enzymes can function in very low pH’s Inhibitors and Activators: enzyme activity is sensitive to the presence of substances that can bind to the enzyme and change its shape inhibitor: a substance that binds to an enzyme and decreases its activity a) competitive inhibitors: compete with the substrate for the same active site, occupying the same site and preventing the substance from binding b) noncompetitive inhibitors: bind to the enzyme in another location, changing the enzymes shape so the substrate can’t bind activator: a substance that binds to an enzyme that increases its activity allosteric site: other sites on an enzyme that inhibitors and activators can bind to cofactors: one or more nonprotein components required by enzymes in order to function, found in the active site of enzymes coenzyme: a nonprotein organic molecule that plays an accessory role in enzyme catalyzed processes by acting as a donor or accepter of electrons Metabolism: the total of all chemical reactions carried out by an organism anabolism: the chemical reactions that expand energy to build up molecules; needs an energy input catabolism: reactions that harvest energy by breaking down molecules; releases energy biochemical pathways: a sequence of chemical reactions in which the product of one reaction becomes the substrate of the next reaction feedback inhibition: control mechanism in which an increase in the concentration of some molecules inhibits the synthesis of the molecule