Chapter 15 Notes
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This 3 page Class Notes was uploaded by Cassidy Zirko on Sunday March 27, 2016. The Class Notes belongs to BCH 110 at University of Montana taught by Scott Samuels in Spring 2016. Since its upload, it has received 12 views. For similar materials see Intro Biology for Biochemist in Biology at University of Montana.
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Date Created: 03/27/16
Chapter 15: Polysaccharides 439445, 448453 15.1 Standard States for Free Energy Changes Lowering eergy dispersal on molecular level is spontaneous What are Standard States? o Standard conditions choice is arbitrary all substances involved in the reaction are in their standard states, also said to be at unit activity o Pure solids and liquids standard states is the pure substance o Pure gases standard state is take as pressure at 1 atm of gas o Solutes standard state is at 1M concentration What do Standard States have to do with Free Energy Change? o Can write any equation relating free energy change for reaction under any conditions ° [ ] [ ]d o ∆ G=∆G +RTln a b , brackets show molar concentrations, R, gas A ] B ] constant, T is absolute temperate o Equation holds under all circumstances reaction doesn’t have to be at equilibrium o Free energy under a given set of conditions depends on value of the standard free energy and concentration of reactants and products o When reaction is at equilibrium, ∆ G =−RTln K eq with the equilibrium constant used in the equation rather than the concentrations 15.2 A Modified Standard State for Biomedical Applications Why do we need a Modified Standard State for Biochemical Applications o Free energy changes includes stipulation that all substances be in standard states o pH is zero if the hydrogen ion concentration is 1M o living cell pH is normally neutral standard state in biochemical practice one that differs from the original standard state only by the change in the hydrogen ion concentrations o free energy changes calculated on basis of modified standard state 15.3 The Nature of Metabolism What is Metabolism? o Metabolism the biochemical basis of all life processes o Molecules of carbs, fats and proteins are processes in a variety of ways to extract energy o Catabolism breakdown of larger molecules to smaller ones o Small molecules are used as a starting point of reactions to produce larger more complex molecules proteins and nucleic acids (Anabolism) o Catabolism and anabolism separate pathways, not just reverse of each other o Catabolism oxidative process that releases energy o Anabolism reductive process that requires energy 15.4 The Role of Oxidation and Reduction in Metabolism How are Oxidation and Reduction Involved in Metabolism? o Oxidationreduction reactions redox reactions those in which electrons are transferred from donor to an acceptor o Oxidation loss of elections o Reduction gain of elections o Reducing agent substance that loses electrons (electron donor, one being oxidized) o Oxidizing agent substance gains electrons (electron acceptor, one being reduced) o Both oxidizing agent and reducing agent are necessary for transfer of elections o Example: strip of metallic zine placed in solution with copper ions o Zinc metal disappears and zinc ions go into solution copper ions removed from solution and copper metal is deposited o Zinc lost two electrons becoming positively charged, was oxidized o Copper gained two elections becoming stable, was reduced o Half reaction separate equation from original that is written as part of the overall reaction o When the half reactions are combined you get the full reaction o Clear example of electron transfer o Biological redox reactions oxidation state of carbon atom changes 15.6 Coupling of Production and Use of Energy Energy cant be used directly need to be shunted into an easily accessible form of chemical energy Coupling of energy producing reactions and energy requiring reactions is central feature in metabolism How do Energy Producing Reactions allow Energy Requiring Reactions to take Place? o Phosphorylation of ADP to produce ATP requires energy supplied by oxidation of nutrients o Hydrolysis of ATP to create ADP releases energy o Energy must be expended to put an additional negatively charged phosphate group on ADP by forming a covalent bond to phosphate group o Entropy loss when ADP is phosphorylated because there are fewer molecules than before o Decrease in electrostatic repulsion on phosphorylation of ADP to ATP o Bond is hydrolyzed when reaction takes place high energy bond reaction in which hydrolysis of specific bond releases a useful amount of energy o Free energy of hydrolysis of organophosphates is higher than that of ATO and able to drive phosphorylation of ADP to ATP o Phosphoenolypyruvate molecule involved in glycolysis high energy compound because of resonance stabilization of liberated phosphate when hydrolyzed o Energy of hydrolysis of ATP not stored energy, electric current doesn’t represent stored energy o Cycling of ATP and ADP is metabolic processes getting energy from production to its uses when it is needed o Oxidation takes place when organisms need energy that is generated by hydrolysis of ATP o Chemical energy is stored form of fats and carbs metabolized as needed o Energy supplied for endergonic reactions comes from hydrolysis of ATP and indirectly from oxidation of nutrients o When we add two chemical reactions to obtain an equation for overall reaction can also add free energy changes to find overall free energy change o Free energy is a state function only depends on beginning and ending values o Exergonic reactions provides energy drive endergonic processes o Coupling percentage of released energy that is used to phosphorylate ADP is the efficiency of energy used in anaerobic metabolism o Break down of glucose goes further under aerobic conditions end products of aerobic oxidation 6 molecules of carbon dioxide and water for every molecule of glucose o Added two reactions and free energies got overall equation and overall free energy change o More ATP produced by coupling process in aerobic oxidation of glucose o
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