Receptors I Flashcards Preview

BMS 242 Core Physiology and Pharmacology > Receptors I > Flashcards

Flashcards in Receptors I Deck (51)
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1

What drug type creates a response in the cell

agonist

2

What is occupation of a drug-receptor governed by?

Affinity

3

What is activation of a drug-receptor governed by?

efficacy

4

What part of a drug receptor reaction is reversible

occupation forming a complex

5

What is the ratio of reversibility of a drug receptor reaction governed by?

affinity of the drug

6

Describe the reversibility of drugs with high affinities

slow reversibility

7

Describe occupancy

proportion of receptors occupied will vary with the drug concentration

8

What does occupancy vary between

0 and 1

9

How much drug is present at 0 occupancy

none

10

How can we measure occupancy

by measuring response

11

Describe the relationship between occupancy and response

high occupancy means there is a large response

12

Can you measure antagonists activity using occupancy

NO

13

Examples of ligands

neurotransmitters, hormones, growth factors, cytokines, drugs, toxins

14

Examples of protein targets

receptors, ion channels, enzymes, transporters

15

Describe a ligand binding practical

tissue prep with radio-ligand, incubation, filtration, rinse, count, data analysis

16

True or False - most ligands bind non-specifically to tissue, filter paper, glass

TRUE

17

How can non-specific ligand binding be reduced

reduced by anti-absorbants

18

What are some examples of anti-absorbants

albumin, collagen, o-catechol

19

What is the function of rinsing in a ligand binding practical

remove unbound radioligand from incubation medium

20

What is a key measurement in receptor ligand assays

specific and non specific binding

21

What are the disadvantages of using a radio ligand

degradation

22

How can you prevent degradation of radio ligands

free radical scavenger, store at low temp, avoid light, incorporation of antioxidant

23

What are radio ligands labelled with

radio active labels

24

Name two radio labels

tritum, iodine

25

What are the disadvantages of tritum

specialised labs required, expensive

26

What are the advantages of tritum as a label

high specific activities, good stability, long half life

27

What are the advantages of iodine as a label

easy and cheap, if aromatic hydroxyl group can be incorporated at high specific activities

28

What are the disadvantages of iodine

more readily degraded, short half life, activity of ligand can be reduced

29

What tissue would you select for your ligand binding practical

tissue that contains the receptors of interest

30

What can the tissue be in the ligand binding practical

isolated membranes, slices, synaptosomes, purified receptors

31

What must incubation preserve

integrity of ligands and binding sites

32

What happens during the tissue incubation period of the ligand binding practical

enzymes are liberated

33

What is the effect of enzymes being liberated during the tissue incubation period

enzymes break down receptors of interest

34

What are the enzymes liberated during the tissue incubation period

proteases

35

How can the effect of enzymes be minimised during the tissue incubation period

protease inhibitors added for peptides, anti-oxidants if ligand is oxidisable

36

What is the temperature during the incubation period

low room temperature to 0 degrees

37

How is the tissue and bound ligand separated from free ligand

filtration or centrifugation

38

What is a problem when separating bound ligand from free ligand during the practical

rate of dissociation of ligand-receptor complex

39

What must speed of separation of bound ligand from free ligand be compatible with

affinity of ligand for receptor

40

What type of separation does lower affinity of ligand receptor require

faster/more efficient separation

41

How do you work out specific binding

subtract non specific binding from total bound

42

How is ligand receptor binding data plotted

semi-logarithmic scale

43

What is saturable binding

specific binding

44

Why is radio-ligand binding saturable

total number of receptors is limited

45

What does the Langmuir equation describe

relationship between receptor occupancy, affinity and drug concentration

46

What is Bmax in the Scatchard equation

maximum amount of drug which can bind specifically to receptors

47

What is F in the Scatchard equation

free ligand concentration

48

What is KD in the scatchard equation

dissociation constant for radio ligand

49

What determines the dissociation constant for the radio ligand

saturation analysis

50

What is KD a measure of

affinity

51

What does high KD show

low affinity