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HUCM Enzyme Definitions
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18
Medical
Graduate
08/07/2011

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Term
A numerically small (low) Km reflects a ? ? of the enzyme for substrate. The rate of reaction is said to be ? order with respect to substrate.
Definition
high affinity
first
Term
A numerically large (high) Km reflects a ? ? of enzyme for substrate because a high concentration of substrate is needed to half-saturate the enzyme.
Definition
low affinity
Term
The rate of the reaction is directly proportional to the ? ? at all substrate concentrations
Definition
enzyme concentration
Term
If the enzyme concentration is ?, the initial rate of the reaction (Vi), as well as that of Vmax, are reduced to one half that of the original.
Definition
halved
Term
When [S] is much less than Km, the velocity of the reaction is approximately proportional to the ? concentration.
Definition
substrate
Term
When [S] is much greater than Km, the velocity is ? and equal to Vmax.
The rate of reaction is then independent of ? concentration, and is said to be ? order with respect to substrate concentration
Definition
constant
substrate
zero
Term
Km does not vary with the concentration of ?
Definition
enzyme
Term
Km is numerically equal to the substrate concentration at which the reaction velocity is equal to 1/2?
Definition
Vmax
Term
The effect of a competitive inhibitor is reversed by increasing ? At a sufficiently high ? concentration the reaction velocity reaches the Vmax observed in the absence of the inhibitor
Definition
[S]
substrate
Term
A competitive inhibitor increases the ? ? for a given substrate.
Definition
apparent Km
Term
On a Lineweaver-Burke plot the Vmax is unchanged but the inhibited and uninhibited reactions show different ? ? intercepts, indicating that the apparent Km is increased in the presence of the competitive inhibitor
Definition
x axis
Term
Noncompetitive inhibition can bind either free enzyme or the ? ?, thereby preventing the reaction from occurring.
Definition
ES complex
Term
Noncompetitive inhibition can't be overcome by increasing the conc. of substrate. Thus, noncompetitive inhibitors decrease the ? of the reaction.
Definition
Vmax
Term
Noncompetitive inhibitors don't interfere with the binding of substrate to enzyme. Thus, the enzyme shows the ? ? in the presence or absence of the noncompetitive inhibitor
Definition
same Km
Term
Noncompetitive inhibition is readily differentiated from competitive inhibition by plotting 1/Vo versus 1/[S] and noting that ? decreases in the presence of a noncompetitive inhibitor, whereas ? is unchanged
Definition
Vmax
Km
Term
Statin drugs like atorvastatin (Lipitor) and simvastatin (Zocor) are examples of ? ?
Definition
Competitive inhibitors
Term
Ex. of noncompetitive inhibitors: some inhibitors act by forming ? ? with specific groups of enzymes
Definition
covalent bonds
Term
An example of a noncompetitive inhibitor is ? forming covalent bonds with sulfhydryl side chains of cysteine in proteins
Definition
lead
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