11 - Signalling between cells II

Question 1

What is an ionotrophic receptor?

Answer 1

binding of a ligand opens an ion permeable pore

Question 2

What is a G-protein coupled receptor?

Answer 2

binding of a ligand activates intracellular G-protein

Question 3

What is an enzyme-linked receptor?

Answer 3

binding of a ligand leads to receptor clustering which activates internal enzymes

Question 4

What is an intracellular receptor?

Answer 4

a membrane permeable ligand binds to a receptor inside the cell

Question 5

G proteins exist as _____

Answer 5

heterodimers

Question 6

What are the subunits of the heterodimer in a G-protein?

Answer 6

alpha, beta and gamma subunits

NOTE: beta and gamma subunits do not dissociate

Question 7

What in angiotensin?

What receptors does it act on?

Answer 7

a hormone produced by the kidneys, which is the most potent vasoconstrictor in the body

acts on the Gq proteins linked AT-1 receptor (which causes SM contraction)

Question 8

What is the key concept with the mechanism of enzyme-linked receptors?

Answer 8

when the ligand binds, the receptors cluster and activate intracellular enzymes

Question 9

What is the mechanism of action of enzymes-linked receptors?

Answer 9

• enzymes are attracted to the receptor and move towards it (to become activated)
• activation of enzymes leads to phosphorylation pf the receptor
• this leads to the binding of signalling proteins in the cytoplasmic domain
• the signalling proteins recruit other signalling proteins and a signal is generated inside the cell

Question 10

What enzymes are most enzyme-linked receptors linked to?

Answer 10

tyrosine kinase enzymes

Question 11

What are the 2 types of intracellular receptors?

Answer 11

type 1 - cytoplasmic

type 2 - nuclear

Question 12

Type 1 intracellular receptors:

1) where are they located?
2) what kind of proteins are they attached to?
3) what are the typical ligands?

Answer 12

1) cytoplasm
2) heat shock proteins
3) steroids

Question 13

What is the mechanism of action of type 1 intracellular receptors?

Answer 13

• the ligand binds to the receptor, which dislocates from the heat shock protein
• the ligand and receptor move into the nucleus together
• it binds to DNA (either causing increase or decrease in transcription)

they are transcription factors

Question 14

Where are type 2 intracellular receptors located?

Answer 14

within the nucleus, already bound to DNA

Question 15

What is the mechanism of action of type 2 intracellular receptors?

Answer 15

ligand comes in, moves through the nuclear envelope and binds to the receptor on the DNA causing changes in transcription