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52 Cards in this Set
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Km: Definition

Km = Substrate at 0.5*Vmax
Km reflects the affinity of the enzyme for its substrate 

Vmax indicates what?

Vmax is directly proportional to the enzyme concentration.


Relationship between Km and affinity

The lower the Km, the higher the affinity
Smaller Km means enzyme is saturated earlier, which means that small amounts of substrate are picked up by the enzyme. 

Reading an inverse curve: Yintercept equals ?

1/Vmax
The higher the Yintercept the lower the Vmax 

Reading an inverse curve: Xintercept equals ?

(1/Km)
The further to the right the xintercept, the greater the Km 

Reading an inverse curve: Slope equals ?

Km/Vmax


Reading an inverse curve: Effect of a competitive inhibitor

Xintercept farther to the right, meaning Km is greater, because you need more substrate to get the same effect as the competitive inhibitor is hogging the enzyme.
The yintercept is the same, meaning Vmax hasn't changed, because there isn't any more enzyme. The slope is greater, because Km has increased while Vmax has stayed the same. 

Reading an inverse curve: Effect of a noncompetitive inhibitor

The xintercept is the same, meaning Km is the same, because the affinity for the enzyme hasn't changed, there's just less of it.
The y intercept has increased, meaning Vmax has decreased, because enzyme has been inactivated by the noncompetitive inhibitor The slope is greater, because Vmax has decreased while Km has stayed the same. 

Competitive inhibitor: Resemble substrate

Yes


Competitive inhibitor: Overcome by increased substrate?

Yes


Competitive inhibitor: Binds active site?

Yes


Competitive inhibitor: Effect on Vmax

Unchanged. The amount of enzyme has not changed.


Competitive inhibitor: Effect on Km

Increased. A lot more substrate needs to be available to seize the active sites.


Noncompetitive inhibitor: Resemble substrate?

No


Noncompetitive inhibitor: Overcome by increased substrate?

No


Noncompetitive inhibitor: Binds active site?

No


Noncompetitive inhibitor: Effect on Vmax

Decreased. Takes the enzyme out.


Noncompetitive inhibitor: Effect on Km

Unchanged. Does not change the affinity for the enzyme.


Volume of distribution: Abbreviation

Vd


Vd: Stands for what?

Volume of distribution


Volume of distribution: definition

Vd = (amount of drug in the body)/(plasma drug concentration)


Volume of distribution: What alters it?

Liver and kidney disease


Where are drugs with a low Vd distributed?

plasma


Where are drugs with a medium Vd distributed?

extracellular space


Where are drugs with a high Vd distributed?

tissues


Clearance: definition

=(rate of elimination of drug)/(plasma drug concentration)
=Vd x Ke where Ke=elimination constant 

Half life: definition

The time required to change the amount of drug in the body by 1/2 during elimination (or during a constant infusion).


What percentage of steady state is a drug at after: 1 half life

50%


What percentage of steady state is a drug at after: 2 half lives

75%


What percentage of steady state is a drug at after: 3 half lives

87.5%


What percentage of steady state is a drug at after: 3.3 half lives

90%


What percentage of steady state is a drug at after: 4 half lives

94%


How many half lives does it take for a drug to reach the following percentage of steady state: 50%

1 half life


How many half lives does it take for a drug to reach the following percentage of steady state: 75%

2 half lives


How many half lives does it take for a drug to reach the following percentage of steady state: 87.5%

3 half lives


How many half lives does it take for a drug to reach the following percentage of steady state: 90%

3.3 half lives


How many half lives does it take for a drug to reach the following percentage of steady state: 94%

4 half lives


Cp stands for what?

target plasma concentration


What is the abbreviation for target plasma concentration?

Cp


In pharmacology, what is F an abbreviation for?

Bioavailability


What is the abbreviation in pharmacology for bioavailability?

F


Loading dose: Definition

Loading dose = (Cp * Vd)/F (where Cp equals the target plasma concentration, Vd equals volume of distribution, and F equals bioavailability)


Maintenance dose: Definition

Maintenance dose = (Cp * CL)/F (where Cp is the target plasma concentration and CL is clearance and F is bioavailability)


Zeroorder elimination: definition

Constant elimination over time regardless of drug.


How does Cp vary with time during zeroorder elimination?

Cp decreases linearly with time.


Zeroorder elimination: Drug examples

Ethanol
Phenytoin Aspirin (at high concentrations) 

Firstorder elimination: definition

Rate of elimination is proportional to drug concentration


Zeroorder elimination vs Firstorder elimination: Comparison

Zeroorder: Constant amount of drug eliminated per unit time
1storder: Constant fraction of drug eliminated per unit time 

How does Cp vary with time during firstorder elimination?

Cp decreases exponentially with time.


Urine: Which species get trapped in urine?

Ionized species


In what kind of environment is the following trapped?: Weak acids

Basic environments


In what kind of environment is the following trapped?: Weak bases

Acidic environments
