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First Aid USMLE Step 1: Pharmacology

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In the Michaelis-Menten kinetics what do the following mean:
Km
Vmax

Draw a typical hyperbolic curve on a Michaelis-Menten Plot, then draw how the addition of a competitive and non-competitive inhibitor would change the kinetics of the reaction.
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In the Michaelis-Menten kinetics what do the following mean:
Km
Vmax

Draw a typical hyperbolic curve on a Michaelis-Menten Plot, then draw how the addition of a competitive and non-competitive inhibitor would change the kinetics of the reaction.
In the Michaelis-Menten kinetics what do the following mean:

Km:
- the concentration of substrate at 1/2 Vmax
- this is INVERSELY related to the affinity of enzyme for its substrate

Vmax:
- maximal velocity at which enzymatic reaction occurs
- is directly proportional to the enzyme concentration

Competitive inhibitor: would raise Km but Vmax is the same

Non-competitive inhibitor: would lower Vmax?
Image: In the Michaelis-Menten kinetics what do the following mean: Km Vmax Draw a typical hyperbolic curve on a Michaelis-Menten Plot, then draw how the addition of a competitive and non-competitive inhibitor would change the kinetics of the reaction.
Draw a Lineweaver-Burke plot. What information do the following intercept points correspond to?

X axis
Y axis
slope
y intercept
x intercept

How do a competitive and non-competitive inhibitor would change the plot?
Draw a Lineweaver-Burke plot. What information do the following intercept points correspond to?

X axis: 1/ [S]
Y axis: 1/V
slope: Km/Vmax
y intercept: 1/Vmax
x intercept: 1/-Km

How do a competitive and non-competitive inhibitor would change the plot?
- reversible competitors cross each other competitively
- non-competitive inhibitors DO NOT!
Image: Draw a Lineweaver-Burke plot. What information do the following intercept points correspond to? X axis Y axis slope y intercept x intercept How do a competitive and non-competitive inhibitor would change the plot?
FOR:
reversible competitive inhibitors
irreversible competitive inhibitors
non-competitive inhibitors

Explain the following properties:
- do they resemble their substrate?
- overcome by an increase in [S]
- bind to the active site of the enzyme
- have an effect on Vmax
- have an effect on Km
- how does it alter kinematics of the original substrate?
Image: FOR: reversible competitive inhibitors irreversible competitive inhibitors non-competitive inhibitors Explain the following properties: - do they resemble their substrate? - overcome by an increase in [S] - bind to the active site of the enzyme - have an effect on Vmax - have an effect on Km - how does it alter kinematics of the original substrate?
What is bioavailability (F)?

What is F for an IV drug?

What is F for an oral drug?
What is bioavailability (F)?
- the fraction of an administered drug reaching systemic circulation unchanged

What is F for an IV drug?
- F = 100%

What is F for an oral drug?
- usually < 100% due to incomplete absorption and first-pass metabolism
What is the volume of distribution (Vd) of a drug? How do you calculate it?

How does the apparent Vd of a plasma-protein bound drug change in disease states?


For the following compartments, what would Vd be approximated as and what kinds of drugs are primarily found in these compartments?
- Blood
- ECF
- All tissue (including fat)
What is the volume of distribution of a drug? How do you calculate it?
- the theoretical volume occupied by a total amount of drug in the body relative to its plasma concentration

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

How does the apparent Vd of a plasma-protein bound drug change in disease states?
- apparent Vd of a plasma-protein bound drug can be altered by liver and kidney disease
- decreased protein binding leads to increased Vd

For the following compartments, what would Vd be approximated as and what kinds of drugs are primarily found in these compartments?
See image included
Image: What is the volume of distribution (Vd) of a drug? How do you calculate it? How does the apparent Vd of a plasma-protein bound drug change in disease states? For the following compartments, what would Vd be approximated as and what kinds of drugs are primarily found in these compartments? - Blood - ECF - All tissue (including fat)