Chapter 6: Enzymes Flashcards
Enzymes are characterized by:
specificity, catalytic power, and regulation
- enzymes typically only convert a select group of substrates to a select group of products
- enzyme reactions typically proceed without undesired side reactions
specificity of enzymes
specific site on/in the enzyme where substrate binds and catalysis takes place
-bound by noncovalent forces
active site
substrate binds to that portion of the enzyme with a complementary shape
lock-and-key model
binding of the substrate induces a change in the conformation of the enzyme that results in a complementary fit
induced fit model
What is catalytic power or rate enhancement?
the ratio of the enzyme-catalyzed rate to the uncatalyzed rate.
Reaction rate does not depend on concentration of…
reactants
Enzymes catalyzed reactions can exhibit zero order kinetics when…
the enzyme’s active site is saturated with substrate
What is the Michaelis-Menten equation?
Vinitial = Vmax [S] / Km + [S]
number of substrate molecules converted into product by an enzyme per unit time, ~when the enzyme is FULLY saturated with substrate~
turnover number
What is a reversible inhibitor?
a substance that binds to an enzyme to inhibit it, but can be released
What is a competitive inhibitor?
binds to the active (catalytic) site and blocks access to it by substrate
What is a noncompetitive inhibitor?
binds to a site other than the active site; inhibits the enzyme by changing its conformation
What is an irreversible inhibitor?
a substance that causes inhibition that cannot be reversed
-usually involves formation or breaking of covalent bonds to or on the enzyme
Irreversible inhibitors can permanently shut off one enzyme molecule, and are often…
power toxins but also may used as drugs
