Chemical Transmission and Receptors

Question 1

Describe ionotropic receptors

Answer 1

Specific ligand activated
Directly alter ionic currents
Rapid response
Doesn’t amplify the signal

Question 2

Describe metabotropic receptors

Answer 2

Indirectly alters ionic currents
Slower response
Amplify the signal

Question 3

Describe receptor tyrosine kinases

Answer 3

Indirectly alters ionic currents by phosphorylating 2nd messengers or the receptor directly
Slower response
Amplify the signal

Question 4

Describe G-protein coupled receptors (GPCRs)

Answer 4

Consists of 7 membrane spanning alpha helices

Guanin nucleotide-binding proteins termed G proteins

Question 5

State the three subunits of GPCRs

Answer 5

Alpha
Beta
Gamma

Question 6

Describe the resting state of GPCRs

Answer 6

Resting inactive state= GDP is bound to a subunit

Question 7

Describe the ligand binding step of activation of GPCRs

Explain influence of GEFs and GAP

Answer 7

Ligand binding promotes a conformational change in heterotrimer and release of GDP and binding of GTP

Guanine exchange factor (GEFs) facilitates this exchange

GTPase (GTPase activating protein, GAP) is associated with g protein activation but cleavage to GDP leads to inactivation

Question 8

Describe the stimulation step of GPCRs

Answer 8

GDP-GTP exchange stimulates dissociation of G Protein complex from receptor

Question 9

GAP proteins involved in GPCRs

Answer 9

Regulation of G-protein signalling

Family of proteins that enhance some alpha subunits and GTPases activity

Question 10

State properties of alpha and betagamma effector molecules

Answer 10

Alpha= water soluble

Betagamma= lipid associated