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Physiology and Pharmacology > Pharmacodynamics - receptors > Flashcards

Pharmacodynamics - receptors Flashcards

1
Q

What are drug concentrations calculated in? Why?

A

Molarity

Because it looks at the number of molecules per L

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2
Q

How is molarity calculated?

A

g/L
___
Mr

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3
Q

What are the different units of molarity?

A

molar, M

millimolar, mM

micromolar, muM

nanomolar, nM

picomolar, pM

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4
Q

How do you get from molar to millimolar?

A

Multiply by 1000

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5
Q

How do you get from millimolar to molar?

A

Divide by 1000

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6
Q

What is a ligand?

A

A molecule or ion that binds specifically to a receptor

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7
Q

How do ligands interact with receptors?

A

Bind to receptors

and then dissociate from the receptor

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8
Q

What is the proportion of ligands that bind to receptors?

A

Enough to reach equilibrium in the reversible reaction

ligand + receptor ligand-receptor complex

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9
Q

What are the effects that a ligand can have on a receptor once it’s bound to it?

A

Can activate it

Can just bind to it with no other effect

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10
Q

What are the types of ligands based on the effect they have on the receptor?

A

Agonists - activate the receptor

Antagonists - bind to the receptor, block it from agonists

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11
Q

What must a ligand have in order to bind to its receptor?

A

It must have affinity for the receptor

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12
Q

What is affinity?

A

The ability of the ligand to bind to its receptor

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13
Q

What must a ligand have in order to activate its receptor

A

Intrinsic efficacy

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14
Q

What is intrinsic efficacy?

A

The ability of the ligand to activate its receptor

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15
Q

What must a ligand have in order to bring about a cell response?

A

Efficacy

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16
Q

What is efficacy?

A

The ability of the ligand to bring about a larger cell response

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17
Q

What are the factors of efficacy?

A

Intrinsic efficacy

Other factors inside the cell, tissue etc.

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18
Q

Do agonists and antagonists have affinity?

A

Yes

because both bind to their receptor

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19
Q

Do agonists and antagonists have intrinsic efficacy?

A

Only agonists do, because only agonists activate the receptor
not antagonists

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20
Q

Do agonists and antagonists have efficacy?

A

Only agonists do, because only agonists activate the receptor to start off the process of bringing about the cell response
not antagonists

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21
Q

Why do antagonists not have efficacy?

A

Because they cannot activate the receptor
so it can’t interact with effector proteins
no cell response

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22
Q

What shape does a graph of x axis-drug concentration against y axis-receptor saturation look like?

A

Rectangular hyperbola

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23
Q

What is Bmax?

A

Maximum binding of receptors

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24
Q

What is Kd?

A

Drug concentration that gives half of Bmax

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25
Q

What does Kd measure? How?

A

Measures affinitiy of drug

The lower the Kd, means lower concentration of drug required to bind to half of the receptors, so drug has higher affinity for receptor
and oppositely too

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26
Q

What shape does a logarithmic graph of x axis-drug concentration against y axis-receptor saturation look like?

A

Sigmoidal curve

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27
Q

What is the difference between concentration and dose?

A

Dose - drug concentration given to patient, at site of action is unknwon

Concentration - known drug concentration at site of action

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28
Q

What shape does a graph of x axis-drug concentration against y axis-size of response look like?

A

Rectangula hyperbola

29
Q

What is Emax?

A

Maximum size of response

30
Q

What is EC50?

A

Drug concentration that gives half of Emax

31
Q

What is EC50 a measure of?

A

Potency

32
Q

What is potency?

A

The ability of a ligand to bind to its receptor, activate its receptor and bring about a cell response of a certain size

33
Q

What are the factors of potency?

A

Affinity

Intrinsic efficacy

Efficacy

Number of receptors

34
Q

What would a logarithmic graph of x axis-drug concentration against y axis-size of response look like?

A

Sigmoidal curve

35
Q

For a ligand-receptor complex, which of the following are fixed and which are variable:

  • affinity
  • intrinsic efficacy
  • efficacy
  • potency
A

Affinity - fixed

Intrinsic efficacy - fixed

Efficacy - variable

Potency - variable

36
Q

Do all of the receptors have to be bound by ligand in order to get the maximum response? Why?

A

No

because of spare receptors

37
Q

What are spare receptors?

A

Receptors that don’t need to be bound to

to get the maximum response

38
Q

Why is it possible for spare receptors to exist?

A

Because of signal amplification
few ligands binding to their receptors can generate a relatively massively response

Responses are limited
can’t continuously increase all the time

39
Q

How does receptor number affect potency?

A

If have a higher number of spare receptors
lower concentration of drug needed to give bigger response
means higher drug potency

40
Q

How does receptor number affect the maximum response?

A

Need to have enough receptors to give maximum response

if have fewer receptors, get smaller response than maximum

41
Q

Can receptor number change?

A

Yes, not fixed

42
Q

How can receptor number change? Why?

A

Can increase in number, with low activity

Can decrease in number, with high activity

43
Q

How does drug tolerance develop?

A

Cells decrease their receptor number

need higher concentration of drug to bring about same-size response next time

44
Q

How do the graphs for x axis-drug concentration against y axis-receptor saturation and y axis-size of response compare if there are no spare receptors?

A

They are the same

same percentage of receptor saturation gives same percentage of size of response

45
Q

How do the graphs for x axis-drug concentration against y axis-receptor saturation and y axis-size of response compare if there are spare receptors present?

A

The size of response curve is to the left of the receptor saturation curve
means smaller percentage of receptor saturation gives bigger percentage of cell response

46
Q

What is intrinsic activity?

A

The ability of the ligand to produce the maximum sized response

47
Q

What are the types of agonists?

A

Full agonists

Partial agonists

48
Q

What are full agonists?

A

Agonists that can bring about maximum response

49
Q

What are partial agonists?

A

Agonists that can only bring about part of the maximum response

50
Q

What are the intrinsic activities of full and partial agonists?

A

Full agonists have high intrinsic activity

Partial agonists have low intrinsic activity

51
Q

What are the efficacies of full partial and agonists?

A

Full agonists have high efficacy

Partial agonists have low efficacy

52
Q

How do spare receptors relate to full and partial agonists?

A

May or may not be spare receptors with full agonists

No spare receptors with partial agonists but still don’t give maximum response

53
Q

Are partial agonists fixed?

A

No

can be converted into full agonists

54
Q

How is a partial agonist converted into a full agonist?

A

By increasing receptor number

still low efficacy at each receptor but enough receptors to add up and give maximum response

55
Q

What are the types of antagonism?

A

Competitive

  • reversible
  • irreversible

Non-competitive

56
Q

What is the most common type of antagonism?

A

Reversible competitive antagonism

57
Q

What is reversible competitive antagonism?

A

Antagonist binds to ligand-binding site on receptor

prevents agonist binding

58
Q

What shape does a graph of x axis-antagonist concentration against y axis-size of response look like?

A

Vertically reflected sigmoidal curve

59
Q

What is IC50?

A

Concentration of antagonist that gives inhibition of 50% of the maximum response

60
Q

What is IC50 a measure of?

A

Antagonist potency

61
Q

How are the effects of reversible competitive antagonism overcome?

A

By increasing the concentration of agonist

so it outcompetes the antagonist and binds to the ligand-binding site on its receptor

62
Q

How do reversible competitive antagonists affect the drug concentration-size of response curve?

A

Cause it to shift to the right

meaning a higher drug concentration is required to give the same-size response

63
Q

What is irreversible competitive antagonism?

A

Antagonist binds to ligand-binding site on receptor
does not dissociate
prevents agonist binding

64
Q

How are the effects of irreversible competitive antagonism overcome?

A

They can’t be

65
Q

How do irreversible competitive antagonists affect the drug concentration-size of response curve?

A

Shift the curve to the right as higher drug concentrations are required to bind to the spare receptors

Suppress the curve as there are not enough available receptors to produce the full response

66
Q

What is non-competitive antagonism?

A

Antagonist binds to allosteric site

reduces effects of affinity or efficacy of agonist at orthosteric site

67
Q

What is the orthosteric site?

A

Site where endogenous ligand binds

68
Q

What is pharmacodynamics?

A

Study of what a drug does to the body

Physiology and Pharmacology (20 decks)

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