Chapters 11 and 12 Flashcards
What do thermodynamics do?
Defines reaction rates and equilibria.
Equilibria linked to standard free energy change for the reaction: ∆G’º
Reaction rates linked to the activation energy of the reaction: ∆G ≠
Catalyzed vs. Uncatalyzed reactions
A catalysed reaction produces the same amount of product as an uncatalysed reaction but it produces the product at a faster rate.
The activation energy for uncatalyzed conversion to products is much greater than that for the catalyzed reaction. This means that the rate constant for the catalyzed reaction, kcat, will be much greater than kuncat, the rate constant for the uncatalyzed reaction.
Kcat>Kuncat (rate constants)
What is the transition state?
What does an enzyme do to help catalyze a reaction?
What does the formation of the transition state mean?
The transitions state is the intermediary state of the reaction, when the molecule is neither a substrate or product.
The transition state has the highest free energy, making it a rare and unstable intermediate. An enzyme helps catalyze a reaction by decreasing the free energy of the transition state.
The formation of the transition state means that there is equal probability of forming
either the substrate or the reactant, this compound is very unstable and high energy.
What happens after we get over the transition state? Why does the graph go down?
After we get over the hill, we have made a product which makes an enzyme/product complex and it is way more stable. Product is released from the enzyme after this, which is why the graph goes down.
What is a cofactor?
An additional chemical component required for enzyme activity such as iron, magnesium, manganese, and zinc
What is a coenzyme?
A complex organic metalloorganic molecule; may be required to carry specific functional groups (example- vitamins)
What is a prosthetic group?
A coenzyme or metal ion that is tightly bound to the enzyme.
What is a haloenzyme?
A catalytically active enzyme that is bound to its coenzyme or metal ion.
We don’t just lose energy, how is it made up? What kinds of reaction differences does this make up?
We make up the energy difference through binding energy. It makes up the difference between catalyzed and uncatalyzed reactions.
What does a positive modulator do?
Decrease in Km and increase in Vmax
What does a negative modulator do?
Increase Km and decrease Vmax
What is the chymotrypsin mechanism?
The chymotrypsin mechanism steps are as follows: The substrate enters the chymotrypsin active site and is held by hydrophobic interactions. The enzyme executes a nucleophilic attack on the carbonyl carbon of the substrate’s aromatic amino acid to form the first intermediate
What is the catalytic efficiency of an enzyme?
Km, Vmax, Kcat/Km
kcat/kM where kcat is the turnover number, or the number of molecules that can be produced per second per active site of an enzyme. KM is a measure of the affinity of the enzyme with the substrate, or the likelihood of binding.
What is the difference between km and Vmax?
Vmax is the maximum reaction velocity at which all enzymes become saturated with substrate. Km is the substrate concentration at which half of the maximum velocity is achieved.
What are the two types of inhibition?
Reversible and irreversible. There are 3 types of reversible inhibition: competitive, uncompetitive, and mixed inhibition
What do the 3 types of reversible inhibition look like?
What does enolase require for catalysis?
Metal ions
What is the function of the metal ions in enolase and what is their job in the active site? What do they stabalize?
Function of metal ions= 2 Mg+ ions
Job: To stabalize the negative charges that result from the oxy anions off the carboxylic acid off the 2-phosphoglycerate molecules.
They stabilize negative charge from the oxygens of the transition state molecule in the active site of the enolase
What are the two phases of chymotrypsin? Which is faster?
Acylation phase (faster)
Deacylation phase.
These two steps are separated by a rapid burst event, a dramatic change in the trajectory of the plot
