Intro to receptors & signal transduction pathways

Question 1

What is signal transduction?

Answer 1

The process whereby information is transmitted inside of the cell

Question 2

Receptor proteins bind “signals” i.e. drugs and endogenous ligands with ______ affinity

Answer 2

high

Question 3

conformational changes in the structure of the receptor protein then convert the extracellular chemical signal into one or more _________ signals

Answer 3

intra-cellular

Question 4

What are the three naturally occurring chemical messengers?

Answer 4

Hormones
Neurotransmitters
Local chemical mediators

Question 5

What is an agonist drugs?

Answer 5

A type of drug that binds to and exerts an affect on a receptor.

Question 6

All agonists are full agonists. True or false?

Answer 6

False - some drugs can be partial agonists

Question 7

What is an antagonist drug?

Answer 7

A type of drug which also binds to a receptor but which does not alter the activity of the receptor, it simply prevents the agonist from binding

Question 8

All antagonists are competitive. True or false?

Answer 8

False - some are non-competitive

Question 9

What are the two main groups of receptor proteins?

Answer 9

Plasma membrane (extracellular) transmembrane receptors 
Cytosolic/nuclear (intracellular) receptors

Question 10

Water soluble drugs are unable to diffuse across membranes. How are they able to exert their effects?

Answer 10

By binding to plasma membrane receptor proteins on the surface of cells

Question 11

How do lipid soluble drugs such as propofol and steroid hormones such as oestriol exert their effects?

Answer 11

Pass through lipid bilayer and bind to intracellular (cytosolic) receptors

Question 12

What are the three families of plasma membrane receptors?

Answer 12

Ligand gated ion channels 
G-protein coupled (GPC) receptors
Tyrosine Kinase (TK) receptors

Question 13

What is the generalised structure of plasma membranes composed of?

Answer 13

extracellular domain
transmembrane domain
intracellular (cytosolic) domain

Question 14

How many subunits does the nicotinic acetylcholine receptor have?

Answer 14

5

Question 15

GPC receptors have a membrane-spanning domain consisting of ___________

Answer 15

7 transmembrane helices

Question 16

Which type of receptor mediates many biological functions e.g. smell, taste, exocytosis?

Answer 16

GPC receptors

Question 17

GPC receptors are coupled to a ____ protein

Answer 17

GTP

Question 18

Signal transduction involves the movement of a G-protein to an ________

Answer 18

effector site

Question 19

What are the stages that result in the activation of a GPC receptor?

Answer 19

ligand binds to receptor
the receptor is activated as a result
the activation of receptor activates G protein that is coupled to it
G protein goes and activates something else at effector site - often but not always adenylate cyclase
Increased conc of cyclic AMP
activated effectors

Question 20

GPC receptors are coupled to a GTP protein. True or false?

Answer 20

True

Question 21

There is only one family of cytosolic receptors. What is it?

Answer 21

Nuclear hormone (steroid) receptors

Question 22

How are nuclear hormone (steroid) receptors characterised?

Answer 22

Presence of ligand binding domain and a DNA binding domain

Question 23

How do ligands of nuclear hormone receptors exert their effect?

Answer 23

Cause the receptor to translocate to the nucleus, where the receptor binds to DNA and acts as a transcriptional regulator

Question 24

Cytosolic receptors regulate gene expression. True or false?

Answer 24

True