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PMCOL 200 > Lecture 2 - Pharmacodynamics (Receptors) > Flashcards

Lecture 2 - Pharmacodynamics (Receptors) Flashcards

1
Q

what is the Law of Mass Action?

A

the rate of a reaction is dependent on the concentration of the reagents and how well they mix together

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2
Q

how fast a drug and receptor bind

A

rate of association

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3
Q

how fast the drug and receptor unbind

A

rate of dissociation

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4
Q

in pharmacology, the “reagents” of a reaction are:

A

the drug and the receptor

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5
Q

at equilibrium, the rates of association and dissociation are equal so:

A

the amount of drug bound to the receptor is stable

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6
Q

what is the equilibrium dissociation constant (Kd)?

A

the ratio of the dissociation constant (Koff) and association constant (Kon) at equilibrium

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7
Q

what does it mean for a drug to have low Kd?

A

the drug binds to the receptor very well (very little dissociation)

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8
Q

what is the Hill-Langmuir equation?

A

[AR] = ([A][Rt]) / ([A]+[Kd])
*A = drug
*R = receptor

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9
Q

the law of mass action equation forms what type of curve?

A

a sigmoidal curve

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10
Q

when [A]=Kd, the concentration of the drug is just enough to:

A

occupy half the receptors (Kd = [Rt]/2)

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11
Q

what two characteristics the law of mass action can be determined using the Hill-Langmuir equation (but more specifically the graph)?

A

the maximum system capability (Rt) and the system sensitivity (Kd)

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12
Q

most drugs interact with receptors in a _____ manner to produce change in the state of the receptor

A

reversible

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13
Q

the binding of a drug and receptor determines the quantitative between:

A

dose and effect

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14
Q

most drugs influence a cellular process, either by interacting with a ____, ____, ____, or _____

A

receptor, channel, transporter, or enzyme

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15
Q

proteins that respond to an external stimulus, and induces a change inside the cell

A

receptors

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16
Q

proteins which form pores in the cell membrane that allow passive movement of ions into or out of the cell

A

channels

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17
Q

movement of ions across the cell membrane through channels is driven by:

A

passive diffusion, and do not require energy

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18
Q

proteins which actively transport molecules across the membrane using ATP or other high energy molecules

A

transporters

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19
Q

types of receptors which are located inside the cell

A

intracellular receptors

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20
Q

in order for drugs to act on an intracellular receptor, they must:

A

cross the plasma membrane

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21
Q

in order for drugs to cross the plasma membrane, they must be:

A

lipid soluble

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22
Q

what is an example of drugs which act on intracellular receptors?

A

steroid hormones

23
Q

a steroid binds to the _____ of a steroid hormone receptor, leading to displacement of _____ or other chaperones, which exposes a DNA recognition domain and leads to _____

A

ligand binding domain (LBD), heat shock protein (HSP), transcription of target genes (receptor enters nucleus and binds DNA)

24
Q

how quickly do steroid hormones act?

A

effects typically have a slow-onset and are long-lasting

25
Q

the largest group of membrane receptors in eukaryotes

A

G-protein-coupled-receptors (GPCRs)

26
Q

how many marketed drugs act at GPCRs?

A

1/3 to 1/2

27
Q

in GPCRs, ligands bind to the extracellular side, and trigger a conformational change that:

A

activates a signalling cascade mediated by intracellular G-proteins

28
Q

GPCRs are made of a single polypeptide that is folded into a globular shape embedded in the plasma membrane called a:

A

7 transmembrane receptor

29
Q

what is the purpose of the extracellular loops of GPCRs?

A

form a pocket where signalling molecules can bind

30
Q

specialized proteins that bind nucleotides guanosine triphosphate (GTP) and guanosine diphosphate (GDP)

A

G-proteins

31
Q

GPCR G-proteins are _____, meaning they have three different subunits (alpha, beta, gamma)

A

heterotrimeric

32
Q

what does the alpha subunit do when the GPCR is activated?

A

the alpha subunit swaps a GDP nucleotide (resting form) for a GTP nucleotide (active form)

33
Q

when GDP is swapped for a GTP on a GPCR, this causes the protein to:

A

dissociate into two parts (alpha and beta-gamma)

34
Q

true or false: when the G-protein dissociates, both subunits remain tethered to the membrane and can interact with other signalling molecules

A

true

35
Q

has GTPase activity that acts like a molecular ‘timer’ to terminate the signal

A

the alpha subunit

36
Q

what happens to the G-protein after GTP is hydrolyzed back to GDP?

A

the inactive G-protein complex reassembles and the system can reset

37
Q

GPCRs can be categorized based on:

A

the type of alpha subunit that is associated

38
Q

what are the three types of alpha subunits?

A

Gs, Gi, and Gq

39
Q

different alpha subunits influence different signalling cascades via effects on _____ or _____

A

adenylate cyclase (AC), phospholipase C (PLC)

40
Q

can influence the activity of a variety of protein types including ion channels

A

beta-gamma subunits

41
Q

one of the most common G-protein mediated signalling cascades is via:

A

adenylate cyclase (AC)

42
Q

list the mechanism of action when a drug binds to a receptor coupled to the Gs signalling cascade

A

1) increased activity of AC
2) production of cAMP
3) activation of cAMP dependent protein kinases (ex: PKA)
4) phosphorylation of targets

43
Q

list the mechanism of action when a drug binds to a receptor coupled to the Gi signalling cascade

A

1) suppressed activity of AC
2) decreased production of cAMP
3) inactivation of cAMP dependent protein kinases
4) no phosphorylation of targets

44
Q

list the mechanism of action when a drug binds to a receptor coupled to the Gq signalling cascade

A

1) increased activity of PLC
2) production of inositol triphosphate (IP3) and diacyl glycerol (DAG) from the breakdown of PIP2
3) IP3 triggers the release of intracellular Ca++ (influences a variety of signalling pathways)
4) DAG activates protein kinase C (PKC) and target substrates

45
Q

activation of tyrosine kinase receptors is driven by _____ in a presence of a ligand, causing the receptors to _____ and become activated

A

dimerization of receptors, autophosphorylate

46
Q

drugs that inhibit or stimulate the activation of tyrosine kinase receptors will influence:

A

downstream signalling molecules

47
Q

the fastest mechanism of signalling in the body depends on:

A

electrical signals generated by ion channel proteins

48
Q

allow ions to cross the membrane rapidly, leading to changes in membrane voltage

A

ion channels

49
Q

different ion channels are controlled by distinct stimuli, such as _____ or changes in _____

A

ligand binding, membrane voltage

50
Q

proteins which open or close in response to the binding of a small signalling molecule (like amino acids or neurotransmitters)

A

ligand-gated channels

51
Q

proteins which response very rapidly to changes in membrane voltage

A

voltage-gated ion channels

52
Q

specialized proteins that assist in the movement of ions, peptides, small molecules, lipids, and macromolecules across a biological membrane, moving the substrate against their concentration gradient (uses energy)

A

active transporters

53
Q

what is an example of an active transporter?

A

the dopamine transporter: which clears dopamine from the synapse

cocaine blocks the dopamine transporter, leading to an accumulation of dopamine in the synapse

PMCOL 200 (8 decks)

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