Lecture 8

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Cell and Systems Biology
Mounir Abou Haidar

Lecture 8SelfAssembly of Viruses Starting form pg55How the viruses assemble themselves This means that the protein recognized the nucleic acid to make up the virus particle This is done in a testing tube and this will hopefully teach us what is really happening inside the cell In a lifecycle of a virus when the virus enters in to the cell it will replicate and the self assemble itself more on this later onSee an outline of the lecture on page 55This lecture transcript will be following that outline preciselyDetails Pg56 Assembly of helical virusesHistory Frankel Conrat described the selfassembly of TMV in 1955 Mixture of RNA and the protein makes a cloudy solution the virus Therefore in right conditions a virus can self assemble identical to the original virus Therefore ProteinRNA virus can assemble in to original formLauffer said that the process is entropy driven it is endothermicThis means that you have to warm up the reactionif you put it on ice the reaction will not occurIn the case of TMV the reaction has to occur in room temperature This type of reaction has to absorb a little bit of heat from the environment in order to occur Exothermic reaction burn hydrogen and oxygen they explode or propane in a tank and they give off a lot of heat Thermodynamic LawsThe first law Conservation of energy which means energy is neither created nor destroyed but it is transformed Second law important to us all processes in nature proceed in direction of maximum disorder entropy This means normally things have the tendency to get disorganized become random Understand the Gibbs free energy formula delta F delta Hdelta TSWhere F useful work H Heat T absolute Temperature and S EntropyFor a reaction to occur the delta F has to be negative So for an exothermic reaction it will give off a lot of heat therefore the delta H is highly negative therefore the delta F will be negative This reaction is nonreversibleIn other cases ex if you take a bit of NACL salt and put it in a glass of water the salt is a crystal that means the atoms in the crystal are well organized they will dissolve This means that the particles go from a very organized structure and dissolve in water to become random go from structure to random However for this to occur you have to stir it and warm it up if you touch the glass you will feel that the glass is cold because the reaction is absorbing heat This is an endothermic reaction In this case we have gone from an organized state to a random state In this case to have delta F negative because the delta H is positive since it absorbed heat we have to increase the S entropy This way by increasing the degree of randomness we can make the delta F to be negative and allowing the reaction to occur Therefore ALL endothermic reactions are entropy driven This means you have to increase the disorder enough in order for the reaction to occur
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