week 4 essential pharmacology

Question 1

how is intercellular communication specific

Answer 1

• chemical signal released only produces a response in those cells that express the right receptor

Question 2

what are the four different type of cell surface receptors

Answer 2

• receptor channels (ionotropic)
• G protein coupled receptors (metabotropic), may be coupled to enzymes or channels
• receptor enzymes
• intern receptors (receptors that interact with the cytoskeleton)

Question 3

what might a G protein couple to

Answer 3

adenylyl cyclase
- produces cAMP as 2nd messenger
- regulates protein kinase A activity
- phosphorylates target proteins and changes their activity
phopholipase C
- produces IP3 and DAG as 2nd messengers
- releases calcium and regulates kinase C activity
- phosphorylates target proteins and changes their activity

Question 4

what are the sources of intracellular calcium

Answer 4

• from internal stores via IP3 or calcium stimulated release from endoplasmic reticulum
• from outside the cell via voltage gated or ligand gated calcium channels
• via inhibition of calcium transport to outside the cell

Question 5

what are the effects of calcium as a second messenger of a G protein

Answer 5

• directly affects the target protein
• binds to calmodulin which then activates target protein (e.g. calcium-calmodulin dependent kinase)
• works via some other calcium binding protein (e.g. troponin)

Question 6

what is the EC50 of a drug

Answer 6

• effective concentration 50
• the concentration of the drug which will produce half the maximal response
• measure of affinity of drug to the receptor
• the higher the affinity the lower the EC50

Question 7

what is the efficacy of a drug

Answer 7

• determined by how good the drug is at activating the receptor

Question 8

what is a full agonist

Answer 8

• high affinity and high efficacy

Question 9

what is a partial agonist

Answer 9

• high affinity and partial efficacy

- will bind to receptor but won’t fully activate it

Question 10

what is an antagonist

Answer 10

• binds to receptor but does not activate it at all

- high affinity no efficacy

Question 11

what are selective agonist and selective antagonists

Answer 11

• one transmitter may act on several receptor subtypes
• selective agonists are drugs that activate only some of these receptors
• selective antagonists are drugs that block only some of these receptors