2008Chapter6post - Ground Rules of Metabolism Catalase =...

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Unformatted text preview: Ground Rules of Metabolism Catalase = enzyme that helps break down alcohol The Chapter 6 liver plays a central role in alcohol metabolism Some people have diseased livers and others have damaged their livers by drinking too much alcohol There are not enough liver donors for all the people who need a liver transplant. Should life-style be a factor in deciding who gets a liver transplant? Liver Enzymes (from video) _______ dehydrogenase (in cytosol) and catalase (in peroxisomes) Break ________ into acetaldehyde Acetaldehyde dehydrogenase Breaks acetaldehyde into _______ acid What Is Energy? Capacity to do work Forms of energy: Potential (________ or arrangement) Kinetic (________) Thermal (________) Chemical (_________, measured in kilocalories) Fig. 6-2, p.92 First Law of Thermodynamics The total amount of energy in the universe remains __________ Energy can undergo conversions from one form to another, but it cannot be _______ or destroyed What Can Cells Do with Energy? Energy inputs become coupled to energy-requiring processes Cells use energy for: C_________ work M_________ work E____________ work One-Way Flow of Energy Second Law of Thermodynamics No energy conversion is 100% ________ Total amount of energy is flowing from high-energy forms to forms ______ in energy *Life does NOT violate this law - earth is not a ________ system Entropy Measure of how much and how far a concentrated form of energy has been _________ after an energy change Life can resist the flow toward maximum entropy only because it is resupplied with energy from the _________ Free Energy Change: G Difference in free energy of final state and free energy of ______ state (G final - G initial) More ___ energy (higher G) Less _______ Greater work capacity Less free energy (lower G) More stable Less _____ capacity G is negative or _____ than zero Exergonic Reactions Energy is _______ Products have less energy than starting substance G is ________ Example: breakdown of ________ G = -686 kcal/mol glucose, a high energy starting substance + 6O2 ENERGY OUT low energy products 6 6 Endergonic Reactions Energy _____ required Product has ____ energy than starting substances Not spontaneous G is _______ 6 6 low energy starting substances ENERGY IN glucose, a high energy product + 6O2 6 6 Reactions Energy changes in chemical work. The Role of ATP Cells "earn" ATP in ____-gonic reactions Cells "spend" ATP in ____-gonic reactions Ca++ Ca++ Ca++ Ca++ Ca++ Ca++ Ca++ Ca++ ____ energy input Pi ATP Fig. 6-7b, p.95 Enzyme Structure and Function Enzymes are _________ molecules They ______ the rate at which reactions approach equilibrium Chemical Equilibrium At equilibrium, energy in the reactants _______ that in the products Product and reactant molecules differ in energy content At equilibrium, ______ of reactant almost never equals amount of product 1:___ ratio at equilibrium Four Features of Enzymes 1) Enzymes do not make anything happen that could not happen on its own. They just make it happen much _______. 2) Reactions do not alter or use up ________ molecules. 3) The same enzyme usually works for both the ________ and reverse reactions. 4) Each type of enzyme recognizes and binds to only _______ substrates. Activation Energy: Ea For a reaction to occur, an energy ______ must be surmounted Enzymes make the energy barrier ________ They do NOT affect the ___ starting substance activation energy without enzyme with enzyme energy released by the reaction G products Enzyme Example: Catalase catalyses reaction that breaks down hydrogen peroxide H2 O2 H2 O + ____ G = -103 kJ/mol Ea uncatalyzed = ____ kJ/mol Ea with catalase = 8 kJ/mol Helps identify Staphylococci sp. bacteria (a) Gram stain positive (b) Catalase postive Why the bubbles? Induced-Fit Model Substrate molecules are _______ together and are oriented in ways that favor reaction Enzyme may ______ the substrate to aid in breaking and forming bonds Enzymes provide a favorable ____environment (acid/base or shut out water) Enzymes may participate directly in reaction by briefly ______ with substrates Hexokinase (green) attaches phosphate group to glucose (red) http://www3.interscience.wiley.com:8100/legacy/college/boyer/0471661791/ structure/hexokinase/hexokinase_intro.htm Allosteric Activation Allosteric activator must bind and change shape of the active site so that substrate can bind Allosteric Inhibition When allosteric inhibitor is bound to enzyme it alters the active site and blocks substrate Feedback Inhibition Fig. 6.12 Example: Formation of tryptophan Factors Influencing Enzyme Activity 1. Temperature Increase in temperature increases molecular collisions, reaction ______ High temperatures ______ bonds and destroy the shape of active site Tyrosinase = heat-sensitive enzyme in _____ pathway -Enzyme is ____ active on warmer parts of cat which end up lighter Fig. 6-13, p.81 2. pH Fig. 6-14a, p.81 3. Salinity Too much or too little salt -interferes with _______ bonds -change ____ shapes of enzymes 4. Enzyme helpers Cofactors = any ___-protein molecule or ion required for proper enzyme function Coenzymes (_______ molecule) NAD+, NADP+, FAD Accept _________ and hydrogen ions; transfer them within cell Vitamins Metal ions (__________) Ferrous iron in cytochromes 5. Enzyme inhibitors Competitive bind to ___ active site Non-competitive binds to a ______ site - i.e. allosteric inhibitor Metabolic Pathways Enzyme-mediated sequences of reactions in cells Biosynthetic (__abolic) ex: photosynthesis Degradative (___abolic) ex: aerobic respiration ENERGY IN ENERGY IN photosynthesis carbon dioxide, water aerobic respiration organic compounds, oxygen ENERGY OUT Redox Reactions Cells release energy efficiently by electron transfers, or ________reduction reactions One molecule gives up _______ (is oxidized) and another gains them (is ________) Hydrogen atoms are commonly released at the same time, thus becoming H+ Electron Transfer Chains Arrangement of enzymes, coenzymes, at cell ____________ As one molecule is _______, next is reduced Function in aerobic respiration and photosynthesis Uncontrolled vs. Controlled Energy Release Bioluminescence Enzyme-mediated reactions that release energy as fluorescent light Luciferin + ____ + luciferase intermediate molecule Intermediate molecule + __________ luciferase + oxyluciferin + AMP + light Firefly Luciferase Enzyme = ______ polypeptide chain with extensive folding Fig. 6-18b, p.102 Why flash? Fig. 6-18c, p.102 How does a firefly turn the light on? _______ control theory - reaction requires oxygen - control supply to photic organ ________activation theory - involves release of messenger molecules that initiates chemical reaction Note: light is a "cool" light (almost _____ efficient) Bioluminescent Bacteria Fig. 6-19, p.103 Fig. 6-20p.103 Review Chapter 6 Page105 Self-Quiz #1-7 Critical Thinking #1, 2, 3, 5 ...
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