1.7 Receptors

Question 1

What are the 4 mains receptor types

Answer 1

-ligand gated ion channels
-G protein coupled receptors
-nuclear receptors
-kinase linked receptors

Question 2

What is the receptor type that is inside the cell

Answer 2

Nuclear receptors

Question 3

Which receptors use only direct coupling with the signalling molecule

Answer 3

-ligand gated ion channels
-kinase linked receptors

Question 4

Which receptor can mediate long term effects

Answer 4

nuclear receptor

Question 5

How long do ligand gated ion channels take to go into effect

Answer 5

milliseconds

Question 5

How long do g protein coupled receptors take to go into effect

Answer 5

seconds

Question 6

How long do nucelar receptors take to go into effect

Answer 6

hours

Question 7

How long do kinase linked receptors take to go into effect

Answer 7

hours

Question 8

Describe ligand-gated ion channels

Answer 8

Membrane bound channels that are an oligomeric assembly of protein subunits around a central pore. Ligands can bind to one or more sites on the channel to open or close the pore gate

Question 9

Give examples of ligand gated ion channels

Answer 9

ionotropic glutamate, nicotinic cholinergic, GABA and 5-HT

Question 10

Give an example of drug use with ligand gated ion channels

Answer 10

Barbiturates bind to GABA receptors to increasee Cl- influx, this causes IPSPs and cell excitability decreases

Question 11

Describe G protein coupled receptors

Answer 11

They are large transmembrane alpha helix proteins that span the membrane 7 times and are attached to a G protein. They either activate or inhibit signal transduction stages

Question 12

What can the effectors of GCPRs be

Answer 12

Either channels opening/closing or enzymes

Question 13

What happens once a GPCR is bound to

Answer 13

There is a conformational change in the receptor which activates the G protein. The G protein then releases GDP and binds to GTP. The GTP-G protein can then split into the GTP bound a subunit and the B dimer. These can then interact with downstream effectors, using cAMP as the secondary messenger.

Question 14

Give examples of some signalling molecules that bind to GPCRs

Answer 14

adrenaline, noradrenaline, dopamine, 5-HT, opiods and Ach

Question 15

Describe kinase linked receptors

Answer 15

Composed of an extracellular receptor domain, a transmembrane helix region and an intracellular kinase domain (which is the effector)

Question 16

What types of responses do kinase linked receptors usually mediate

Answer 16

Cell growth and responses to metabollic stimuli

Question 17

What happens once the kinase domain in the kinase linked receptors are activated

Answer 17

The kinase catalyses the autophosphorylation of tyrosine residue in target proteins in the cell, then the tyrosine residues then bind to tyrosine kinase enzymes which remove a phosphate group from ATP.

Question 18

Describe nuclear receptors

Answer 18

Receptors inside the cell (either in the nucleus or the cytoplasm) that can only mediate the effects of lipid soluble hormones

Question 19

Give some examples of signalling molecules that can activate nuclear receptors

Answer 19

Steroid hormones, thyroid hormones and vitamin D

Question 20

What happens once nuclear receptors are activated

Answer 20

They bind to DNA and promote or supress the transcription of certain genes

Question 21

Give examples of drug use with nuclear receptors

Answer 21

Many agonists can bind to the receptors and increase the receptor interactions so that the effects on transcription are furthered. However, many antagonists can bind to the receptors and block the receptors from being activated by any signalling molecules, thus reducing the effects on transcription.

Question 22

What shape do dosage response curves usually take on

Answer 22

Sigmoidal (S shaped)

Question 23

Describe the 3 stages in a sigmoidal curve

Answer 23

lag phase- at low doses, there is little response in effect

linear phase- at intermediate doses, the response increases proportionately

plateau phase- at higher doses, the response levels off

Question 24

What is EC50

Answer 24

The dosage needed to give half of the maximum response

Question 25

What is EC50 used to measure and what would a high EC50 indicate

Answer 25

It is used to measure potency and a high EC50 would indicate a low potency

Question 26

What is efficacy at the molecular level

Answer 26

The ability of a drug to produce an effect

Question 27

What is efficacy at the organism level

Answer 27

The maximum effect of a drug (seen by how high up the y axis of the dosage response curve it goes)