ch 13 Flashcards
oxidoreductases
an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another, the oxidant, also called the electron acceptor. This group of enzymes usually utilizes NADP+ or NAD+ as cofactors.
transferases
enzyme that catalyze the transfer of specific functional groups from one molecule to another.
hydrolases
enzymes that are commonly used as biochemical catalysts utilizing water to break a chemical bond in order to divide a large molecule into two smaller ones.
lyases
an enzyme that catalyzes the breaking (an elimination reaction) of various chemical bonds by means other than hydrolysis
isomerases
an enzyme that catalyzes the conversion of a specified compound to an isomer.
ligases
a ligase is an enzyme that can catalyze the joining (ligation) of two large molecules by forming a new chemical bond.
what is vmax
maximal reaction rate or velocity of an enzymatically catalyzed reaction when the enzyme is saturated with its substrate
why does vmax occur or why does the reaction plateau?
the active site is saturated with substrate
what is Km
the substrate concentration at half of the Vmax (measure of how tight an enzyme to a substrate)
from an evolutionary standpoint, why would an enzyme have adapted to have those different Km values?
the natural concentration of a substrate is reflected by the body: low Km: enzyme binds very tightly (low sub conc) high Km: enzyme binds losely (higher sub conc)
what is the Kcat
Vmax/Et the rate of the substrate being made into product unit (1/sec)
what is the turnover number?
how much product is being formed per unit enzyme per unit time when the enzyme is fully saturated with substrate
Catalytic efficiency
ratio of Kcat to Km
what is the significance of Kcat/Km
gives us the catalytic efficiency
low km is what
higher affinity
x intercept for a linegraph is what
x=-1/km
y intercept for a linegraph
y=1/vmax
competitive inhibitor
resembles the substrate and therefore also binds to the active site of an enzyme decreasing the amount of binding of the substrate or ligand to enzyme. BINDS TO THE ACTIVE SITE
uncompetitive inhibitor
binds to a different site of the enzyme AFTER the enzyme-substrate complex has formed thus preventing the ES complex from forming product. RARE
noncompetitive inhibitor
binds to a different site of the enzyme and changed the structure of the enzyme; thus blocking the enzyme from binding to substrate which stops enzyme activity.
what do all three inhibitors have in common?
ITS REVERSIBLE! REVERSIBLE COVALENT BOND
what is the km and vmax of a competitive inhibitor
km higher vmax same
what is the km and vmax of an uncompetitive inhibitor
km lower vmax lower
what is the km and vmax of a noncompetitive inhibitor
pure: km same vmax lower
what makes an irreversible inhibitor irreversible?
it makes a covalent bond that is irreversible
acid catalyst works best at what pH
lower Ph’s
basic catalyst works best at what ph
higher Ph’s
why is aspirin irreversible effect only last a few hours in the body?
body synthesizes more enzyme
the irreversible inhibitor is similar in kinetics to what reversible inhibitor
noncompetitive inhibitor
to be effective enzymes must be present at the same concentration as their substrate
false
enzymes increase the equilibrium constant for the reaction thus favoring product formation
false
enzymes increase the rate at which substrate is converted to product
true
enzyme ensure that all substrate is converted to product.
false
enzymes ensure that all product is more thermodynamically stable than the substrate
false
what do the lines in a lineweaver burk plot look like for competitive inhibition
they are perpendicular, theyre crossed
what do the lines in a lineweaver burk plot look like for uncompetitive inhibition
they are parallel, they do not cross
what do the lines in a lineweaver burk plot look like for noncompetitive inhibition
they start from the same point on the xaxis, they meet at the x axis
what is the diffusion rate for best efficiency
10^8 or 10^9 m-1 s-1
what slope for lineweaver plot
km/vmax
