BCHM 307 1st Edition Lecture 28Outline of Last Lecture I. Polymerase Chain ReactionA. Taq PolymeraseII. DNA MutationsA. SNPsB. IndelsIII. Northern BlottingIV. MicroarraysOutline of Current Lecture I. ThermodynamicsA. Endothermic Vs. ExothermicB. Gibbs Free EnergyC. Change in Free EnergyII. Change in Free Energy under Standard ConditionsIII. ATP HydrolysisCurrent LectureThe 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 inG, ∆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. Thishelps to drive thermodynamically unfavorable reactions
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