Catalysis Flashcards
What would contribute to lowering change in Gcat
Larger change in S
Smaller change in H
two symbols for activation energy
ΔG is also referred to as Ea
What is the Arrhenius Equation
How does lowering Ea affect reaction rate kcat
Higher reaction rate kcat
How does making the entropy change larger (less negative) effect change in Gcat
Lowers Gcat
what the equation for change in G
Change in all but time
G = H-TS
Describe the two ways in which entropy is affected in the equation E+S –> ES? When would this type of reaction proceed?
Free enzyme becomes much more ordered which decreases entropy
Substrate becomes highly ordered, so entropy decreases again
This ordering process would only occur spontaneously if other interactions compensated for the loss of entropies of the enzyme and substrate
3 things about acid base catalysis
Requires proton donors and acceptors
The bases can also work as nucleophiles to form intermediate
Charges can serve to stabilize TS more than S
Describe the Sn2 mechanism (Glu35 and Asp52)
Asp52 acts as nucleophile and Glu35 as acid to facilitate the leaving group
Glu35 then acts as base to activate water, and Asp-52 as leaving group
Generation of product
T/F one amino acid can have multiple roles in multiple steps of a reaction
True, ex: HIV protease dimer, Asp25 has multiple roles
What do isomerases do
Extracts proton and gives it back to a different position
Mechanism of enolase (Lys345, Glu211)
Lys345 abstracts a proton by base catalysis, two Mg2+ ions stabilize the enolic intermediate
Glu211 facilitates the elimination of the OH group by acid catalysis
Nucleophile, electrophile, Base, and acid
Nucleophile: Have a lone pair, which they use to bond to another atom
Electrophile: Electron loving, looking for a lone pair
Acids: Hydrogen donor
Bases: Hydrogen acceptor
