Biochem Lecture 10 Flashcards
(31 cards)
What is an oxidoreductase?
Catalyzes oxidation-reduction reactions.
What are transferases?
Catalyze transfer of C-, N-, or P- containing groups.
What are hydrolases?
Catalyze cleavage of bonds by adding water.
What are lyases?
Catalyze cleavage of C-C, C-S and certain C-N bonds.
What are isomerases?
Catalyze racemization of optical or geometric isomers. Racemization is producing equal quantities of the enantiomers of a substance.
What are ligases?
Catalyze formation of bonds between carbon and O,S,N coupled hydrolysis of high energy phosphates such as ATP.
What is a cofactor with enzymes?
A small molecule required for the catalytic activity of an enzyme. They can be metal ions or coenzymes.
What is a coenzyme?
When a cofactor is an organic molecule.
What is a cosubstrate?
When a cofactor is only transiently associated.
What is prosthetic group?
When the cofactor is permanently associated with a protein, such as a heme group in Hb.
What is the difference between a holoenzyme and an apoenzyme?
Holoenzymes are the active enzyme-cofactor complex.
Apoenzymes lack the cofactor.
What is a substrate?
It is the molecule undergoing the reaction with an enzyme.
How do active site and substrate interact?
The active site has a 3d physical shape that is complimentary to the shape of the substrate. It is a physical and chemical attraction.
What is the induced fit model for the binding of a substrate?
It says that the binding of a substrate distorts the shape of both the substrate and the enzyme. The active site becomes complimentary to the substrate after it is bound.
Are enzymes stereo-specific?
They are. The right enantiomer is needed.
What is the free energy of a molecule?
The amount of energy available to do work.
What is the ground state of a molecule or substance?
The normal energy state of a molecule. The lower the free energy, the more stable a molecule is.
How is the delta G of a reaction calculated?
Delta G= G-Products (minus) G-Reactants
What kind of number will delta G be for an energetically favorable reaction?
It will be negative, which signifies that the products have less energy than the reactants.
What is activation energy?
It is the energy needed to get from the energy state of the substrate to the energy level of the transition state. It is the energy needed to carry out a reaction. It takes energy to break bonds and make new ones, essentially.
What does the rate of a reaction depend on?
It depends on the activation energy. The lower the energy needed for the reaction, the faster it will go.
What does delta G tell us about a reaction?
- Where the equilibrium point will be
- If the reaction is energetically favorable
- It does not tell anything about the rate of reaction
How do enzymes speed up reactions?
They lower the activation energy and therefore increase the rate. They lower the energy of the transition state by stabilizing it. Enzymes often are more complimentary to the transition state than to the substrate.
How is the net energy of a reaction changed when catalyzed vs uncatalyzed?
There is no difference in the overall delta G for a reaction whether a catalyst is used or not. This is because the beginning and final states remain the same. It is the transition state that is changed.
