Bioenergetics Principles of Bioenergetics PDF

 Bioenergetics : The quantitative study of energy transductions in living cells and the physical-chemical nature underlying these processes. It’s a branch of biochemistry concerned with transformation of energy and use of enzymes by living system The Flow of Electrons Provides En...

 Bioenergetics : The quantitative study of energy transductions in living cells and the physical-chemical nature underlying these processes. It’s a branch of biochemistry concerned with transformation of energy and use of enzymes by living system The Flow of Electrons Provides Energy for Organisms Autotrophes Heterotrophes All these reactions involving electron flow are oxidation- reduction reactions  LAWS OF THERMODYNAMICS □ We need to understand System, Heat, and Work FIRST LAW (Law of conservation of energy) Energy can't be created nor destroyed but changed from one form to other The total E leave the system = Total E enters the system – stored internal E In biological recation inside cell System: We are interested in Enthaply H ΔH = H product – H reactants Exothermic Or Endothermic  LAWS OF THERMODYNAMICS SECOND LAW (The equilibrium constant is a measure of Directionality) ΔG: calculates how far from equilibrium a reaction lies under specific conditions and how much energy will be released to reach equilibrium ΔG under specific standard conditions Keq = 1  SECOND LAW (Law of thermodynamic spontaneity, Possibility) 1Physical chemical changes give useful energy undergo irreversible degradation into a random form called entropy 2 total amount of energy in this universe declines with time Enthalpy H (The total energy of a system) is equal to: Free energy G (The usable energy) + entropy S (the unusable energy). ∆G = ∆H – T∆S (Exergonic OR endergonic) When ΔH is highly negative and ΔS is highly positive (rxn. is favorable)  LAWS OF THERMODYNAMICS Keq > 1.... ΔG has negative value.... Reaction goes spontaneoslay to the right (Forward) A+ B --------------------C+D Keq < 1.... ΔG has positive value.... Reaction goes spontaneoslay to the left (Reverse)  ENERGY Useful Useless [Entropy] Free energy can do work at constant P, T Heat Energy do work at constant P, varying T this impossible in livings  Entropy Degree of randomness and disorderness Change within………to explain this follow the following examples Tea kettle Glucose oxidation Glucose + 6O2 6CO2 + 6H2O Information entropy  nd Aspects of 2 Law 1. We must know system, surrounding, and universe system 2. Standard state in which pH=7, T=298K, Concentration=1M, Atm.P=1 Surrounding 3. Enthalpy H=E+PV , enthalpy means warm within, or heat content , E=internal energy, PV pressure times volume. Universe 4. Change in free energy is given by ΔG = ΔH - TΔS that is change in free energy ,enthalpy and entropy respectively 5. When chemical reaction proceeds toward equilibrium then: S increased and ΔS positive ΔG decreased or negative ΔH negative ( when system looses heat), and positive when system absorbs heat Nucleophiles: functional groups rich in electrons and capable of donating them Electrophiles: electron-deficient functional groups that seek electrons The relative electronegativities: F>O>N>C=S>P=H Cleavage of a C-C or C-H bond  Equilibrium Constants and Standard Free-Energy Change For the reaction: aA + bB cC + dD o’ c c ln([C] [D] d /[A] a [B] )b = ΔG reaction + RT ΔG reaction At equilibrium: Keq = [C][D]/[A][B] and ΔGreaction = 0, so that: ΔG o’ = -RT ln K reaction eq The standard free-energy change is directly related to the equilibrium constant Standard free-energy changes are additive Equilibrium constants are multiplicative