Lecture 4 - Thermodynamics and Catalysis Flashcards
1st rule of thermodynamics
Energy cannot be created or destroyed, only transformed
Define systems and surroundings
system–> something that we define
Surroundings –> everything else
universe=system+surroundings
Exothermic v Endothermic
Exothermic –> heat released
Endothermic –> heat taken up
Exergonic v Endergonic
Exergonic –> release of energy
Endergonic –> energy taken up
2nd law of thermodynamics
Systems have a tendency to increase entropy
How can reaction occur even if entropy of system decreases?
Entropy of surroundings may increase
If the enthalpy change is great enough to make deltaG negative
What is Gibbs free energy
1) amount of energy from a reaction free to do useful work
2) measure of the distance of a system from equilibrium
Does deltaG tell us about speed?
NO just indicates which reaction is favourable
How do you calculate deltaGdot and what does it represent
the Gibbs free energy available under standard conditions
deltaG=-RTlnQ
If deltaG is negative, products are favoured
How can you get a reaction with a positive deltaG to proceed
Couple it with another reaction (ex hydrolysis of ATP) such that the net deltaG is negative
What is an enzyme
Protein, a biological catalyst that increase the rate of reaction by lowering the activation energy by providing an alternate pathway for the reaction to occur. Is not consumed by the reaction
Can convert between forms of energy
What does an enzyme change
Changes rate of reaction. Doesn’t affect the equilibrium position at all. Speeds up both the forward and the reverse rate of reaction so that the equilibrium position is reached faster
what is the transition state
High energy intermediate state
enzyme reduces the energy of activation
Describe the active site
small cleft or crevice in the enzyme where it bonds to the substrate through multiple weak interactions
Describe the lock and key hypothesis
Substrate has shape that matches exactly to the enzyme. The problem is that this would be a very stable interaction, thus the intermediate is unlikely to form
