BIOL1007 Lecture Notes - Lecture 5: Thermodynamics, Enzyme, Activation Energy
19 May 2018
School
Department
Course
Professor
Appreciate the difference between the thermodynamic and kinetic properties of a
reaction
The change in free energy (delta G) - available energy to do useful work
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Enthalpy (delta H) - total energy
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Entropy (delta S) - energy utilised in wiggling and jiggling (nervous energy)
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Screen clipping taken: 23/08/2017 9:52 PM
At equilibrium ∆G = 0
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∆S decreases when temp lowered (e.g. jelly, when cooled less movement)
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Free energy
Organisms = open system, so matter and energy can continually flow in and out of cell
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Cell needs LOTS OF FREE ENERGY TO DO WORK ie. Needs to be far from equilibrium and away from ∆G=0
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Cell exists in a STEADY STATE (THIS IS NOT AT EQUILIBRIUM)
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Equilibrium only achieved at death
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Equilibrium vs steady state
Level of the starting substrate and level of the product
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Substrate has more energy than the product = THERMODYNAMICALLY FAVOURABLE ie. -∆G
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Both substrate and product 1M
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25 degrees
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1 atm
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Ph 7
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Standard conditions - denoted by ∆G0'
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Screen clipping taken: 23/08/2017 10:03 PM
Thermodynamics
Free energy (G) is a certain number
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Substrate has more free energy than product so bar is higher
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Under standard conditions
L5 - Enzymes
Wednesday, 23 August 2017
10:11 AM
Mod 1 Information transfer Page 1
Screen clipping taken: 23/08/2017 10:08 PM
∆G = 0 (total free energy difference)
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Only way we can get to equilibrium and balance it out is to change amount of substrate and/or product
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Equilibrium favours the product
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Keq >> 1
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Screen clipping taken: 23/08/2017 10:10 PM
At equilibrium
Kinetics - rate of the reaction
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Reactions need to exceed barrier as molecules rearrange
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Activation energy ∆G# = height of the barrier
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Kinetics vs thermodynamics
the thermodynamics, only lowers activation energy
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∆G0'
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Keq
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Adding enzymes DOES NOT change
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If reaction is exergonic (free energy term) without enzyme it will be with one (ie. If reaction is thermodynamically
favourable without enzyme it will be the same with an enzyme)
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If reaction is endergonic without an enzyme it will be with one (ie. If reaction not thermodynamically favourable
without enzyme, it will be thermodynamically favourable with one)
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Enzymes speed up the reaction
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explain briefly how enzymes act as catalysts
Mod 1 Information transfer Page 2
Document Summary
Appreciate the difference between the thermodynamic and kinetic properties of a reaction. The change in free energy (delta g) - available energy to do useful work. Entropy (delta s) - energy utilised in wiggling and jiggling (nervous energy) Organisms = open system, so matter and energy can continually flow in and out of cell. S decreases when temp lowered (e. g. jelly, when cooled less movement) Cell needs lots of free energy to do work ie. needs to be far from equilibrium and away from g=0. Substrate has more energy than the product = thermodynamically favourable ie. - g. Cell exists in a steady state (this is not at equilibrium) Level of the starting substrate and level of the product. Substrate has more free energy than product so bar is higher. Only way we can get to equilibrium and balance it out is to change amount of substrate and/or product.
