Receptors 2

Question 1

some proteins are turned on when ______ and some are turned off when ________.

Answer 1

Phosphorylated

Question 2

what does desensitization do?

Answer 2

diminishes the response of receptor due to prolonged or repeated agonist exposure.

Question 3

what is internalization?

Answer 3

when a receptor and ligand are formed into an endosome. recycling can happen. downregulation, sequenstration.

Question 4

what is degradation in regards to receptor activity?

Answer 4

some that are internalized become degraded by lysosomes. This happens when defect occurs after recycling for a while.

Question 5

What is the desensitization mechanism?

Answer 5

phosphorylation, conformational changes.

Question 6

what does beta-arrestin do?

Answer 6

binds to receptor causing desentization and internalization

Question 7

What happens to receptor in order for beta-arrestin to bind?

Answer 7

receptor get phosphorylated.

Question 8

the -COOH term is located where?

Answer 8

intracellularly

Question 9

The N term is located where?

Answer 9

Extracellularly

Question 10

What are the subunits of a g protein?

Answer 10

alpha, beta, gamma

Question 11

What does G-alpha-s do?

Answer 11

stimulates cyclic AMP production

Question 12

What does G-alpha-i do?

Answer 12

inhibits cyclic AMP production

Question 13

What does G-alpha-q do?

Answer 13

Activates phospholipase C, increase intracellular calcium

Question 14

What does G-alpha-12/13 do?

Answer 14

promotes growth and differentiation

Question 15

do the beta subunits also have signaling functions?

Answer 15

yes they do

Question 16

describe is the first “step” in the G protein cycle?

Answer 16

in the resting state the alpha and Beta-gamma subunits are associated with one another. GDP is bound to the alpha subunit. 1. An agonist binding 2. GTP-GDP exchange 3. G-protein activation

Question 17

What is the second “step” in the G-protein cycle?

Answer 17

binding of an extracellular ligan (agonist) to a G-protein-coupled receptor causes the exchange of GTP and GDP on the alpha subunit (GTP NOW ON ALPHA SUBUNIT)

Question 18

what is the third “step” in the G-protein cycle?

Answer 18

the beta-gamma subunit dissociate from the alpha subunit. the beta-gamma subunit diffuse and interact with effect proteins. The interacted with the effector making it activated.

Question 19

What is the fourth “step” in the G-protein cycle?

Answer 19

the alpha subunit can hydrolyze the GTP to a GDP to become unactive again which it does. This causes agonist unbinding. The subunit associate back together.

Question 20

What G protein does the pertussis toxin affect?

Answer 20

G-alpha-i

Question 21

What does the pertussis toxin do to the Gai?

Answer 21

it locks them in an GDP bound state leading to under activation of Gai

Question 22

What G protein does the cholera toxin effect?

Answer 22

G-alpha-s

Question 23

What does the cholera toxin do to G-alpha-s?

Answer 23

locks the protein in an active state leading to over activation

Question 24

What is the mechanism of action of the cholera toxin?

Answer 24

modifies Gs protein and keeps it active

Question 25

In cholera-induced-diarrhea, what does the over activation of the Gs protein lead to in regards to cAMP?

Answer 25

there is an overproduction of cAMP

Question 26

in Cholera-induced-diarrhea, what does the overproduction of cAMP lead to?

Answer 26

Stimulates PKA in enterocytes

Question 27

in Cholera induced diarrhea what does the stimulation of PKA in eterocytes lead to?

Answer 27

PKA stimulates Cl- channel sensitivity and results in an abnormal high concentration of Cl- in intestinal lumen

Question 28

in cholera induced diarrhea, what does the high concentration of Cl- in the intestinal lumen cause?

Answer 28

The osmosis force drive H2O and Na+ to enter intestinal lumen

Question 29

What is the symptoms of cholera toxin?

Answer 29

severe diarrhea and dehydration

Question 30

What receptors are associated with Gq protein?

Answer 30

Alpha 1/Muscarinic 1,3,5

Question 31

What receptors are associated with Gi/Go proteins?

Answer 31

alpha 2/Muscarinic 2,4

Question 32

What receptors are associated with Gs protein?

Answer 32

Beta 1,2,3

Question 33

What is the receptors M1, 3,5 and alpha1 with Gq protein main mechanism?

Answer 33

activate phospholipase C to hydrolyze PIP2. Increases IP, Cytoplasmic Ca2+, diacyclglycerol, PKC

Question 34

What is the main mechanism of Gi/Go with the receptors M2, M4, and A2?

Answer 34

decrease adenylyl cyclase and cAMP

Question 35

What is the main mechanism of Gs with B1,2,3?

Answer 35

increase adenylyl cyclase and cAMP

Question 36

What is the most inactive state of G protein?

Answer 36

G alpha subunit bound with GDP and associated with beta and gamma subunits

Question 37

Activation of which receptor most likely will initiate an action potential?

Answer 37

Nicotinic AChr

Question 38

What intracellular reservoir from which calcium is release?

Answer 38

ER

Question 39

What happens when adenylyl cyclase is stimulated by G-alpha-s? what happens after that? (B1 like Receptor)

Answer 39

adenylyl cyclase will convert ATP to cAMP. cAMP then activates PKA which phosphorylates a number of specific cytosolic proteins

Question 40

What happens when Gaq stimulates PLC (M1 like receptors) ?

Answer 40

PLC cleaves the membrane PIP2 into DAG and IP3. DAG diffuses in the membrane to activate PKC, which then phosphorylates specific cellular proteins

Question 41

What does DAG do in the signal transduction through M1 like receptors?

Answer 41

DAG diffuses in the membrane to activate PKC, which then phosphorylates specific cellular proteins

Question 42

What does IP3 do in the signal transduction through M1 like receptors?

Answer 42

IP3 stimulates the release of Ca2+ from the ER into the cytosol. Calcium release also stimulates protein phosphorylation events the lead to changes in protein activation.