BCHM 307 1st Edition Lecture 28 Outline of Last Lecture I Polymerase Chain Reaction A Taq Polymerase II DNA Mutations A SNPs B Indels III Northern Blotting IV Microarrays Outline of Current Lecture I Thermodynamics A Endothermic Vs Exothermic B Gibbs Free Energy C Change in Free Energy II Change in Free Energy under Standard Conditions III ATP Hydrolysis Current Lecture The lecture starts with the new topic of thermodynamics This is a background chapter that will help us to understand the biological processes coming up in later chapters First we need to know the first law of thermodynamics This states that energy cannot be created or destroyed but converted from one form to another The second law of thermodynamics states that all systems tend to become more disorganized As with all things in nature biological systems cannot violate these laws Reactions usually occur when they are exothermic which means they release heat These types of reactions often lead to an increase in entropy which is disorder Reactions can also be isothermic which don t give off heat or endothermic which absorb heat One type of reaction measurement is Gibbs free energy G This measures the spontaneity of a reaction The spontaneity refers to the reaction favoring to make products not how fast this is done G cannot be measured directly though Instead we measure the change in G G G is equal to H minus T S where H is the difference in enthalpy T is the absolute temperature in degrees Kelvin and S is the change in entropy of the universe When G is These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute negative the reaction is said to be spontaneous When G is zero the reaction is at equilibrium When G is positive the reaction is said to be non spontaneous G can only be found under specified conditions You must know the concentrations of all reactants and other cellular aspects that can be hard to calculate Therefore G is often used It describes the free energy change under a set of standard conditions The standards are a temperature at 25 degrees Celsius pressure at 1 atm and all solutes excluding water at 1 M concentration The problem with this comes up if hydrogen ions are involved in the reactions This would cause the pH to be 0 To fix this problem biochemists often work with G This is the free energy change under standard conditions at a pH of 7 0 The equation to find this is equal to 2 303 R T log Keq R is the gas constant equal to 8 315 J mol K T is the temperature in Kelvin Keq can be found by taking the concentration of the products divided by the concentration of reactants The common form of energy in biochemistry is ATP ATP hydrolysis has a high G at 30 5 kJ mol 1 This means that the reaction is spontaneous This is very favorable in biology The large negative value indicates that the reaction is highly favored towards the products This is why many biological reactions that are not as favorable are coupled to the ATP hydrolysis This helps to drive thermodynamically unfavorable reactions forwards
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