chapter 14 sensory and signal transduction

Question 1

what does epinephrine bind to

Answer 1

b-adrenergic receptor

Question 2

which molecule is changed when a photon binds rhodopsin

Answer 2

11-cis-retinal til 11-trans retinal

Question 3

what could be an inhibitor of epinephrin’s binding to B-adrenergic receptor

Answer 3

carazolol

Question 4

G-protein consists of

Answer 4

3- domains
alpha binds the nucleotide (p-loop NTPase)
beta
gamma

Question 5

What happens when GTP is bound to G protein

Answer 5

the B and Y subunits dissociate. so alpha can transmit the signal to other targets

Question 6

one hormone-complex can stimulate the nucleotide exchange in many

Answer 6

G-proteins

Question 7

what does cAMP activate and how does it do it

Answer 7

protein kinase A

by binding to the regulatory chains releasing the catalytic domains which are active on their own

Question 8

what does PKA or protein kinase A consist of

Answer 8

2 regulatory chains

2 catalytic domains

Question 9

what does PKA stimulate besides the activation of downstream targets

Answer 9

it activates the expression of specific genes by phosphorylating a transcriptional activator called the cAMP response element binding protein (CREB)

Question 10

how is the adrenergic receptor deactivated

Answer 10

GRK2 phophorylates the carboxyl-terminal of the hormone-receptor complex
B-arrestin binds to the phosphorylated hormone receptor complex and diminishes the ability to activate G proteins

Question 11

PIP2

Answer 11

phosphatidylinositol 4,5 bisphosphate cleaved by phosphlipase triggered by the angiotensin iI receptor, yielding diacylglycerol DAG + inositol 1,4,5-trisphosphate

Question 12

what does DAG do

Answer 12

remains in the plasmamembrane. activates protein kinase C phosphorylating many serine and threonine residues in many protein targets. Also requires that the protein kinase C is bound to ca2+

Question 13

what makes ca2+ able to inducee structural changes in proteins

Answer 13

because it has a capacity to be coordinated to several ligands (6-8) oxygen atoms. allowing it to cross-link different segments of a protein

Question 14

calmodulin

Answer 14

regulatory protein four ca2+ bindingssites
EF-hands (helix loop helix)

calmodulin regulates calomodulin dependent protein kinases, that phosphorylate many targets regulating fuel metabolism, neurotransmiter synthesis, release and so on.

ca2+ coordinated by 7 oxygen atoms

Question 15

in insulin receptor the tyrosine kinase is

Answer 15

a part of the receptor

Question 16

the activation in insulin receptor

Answer 16

lies in the center of the structure

when the tyrosin residues are phosphorylated the activation loop crosses around making the structure more compact

Question 17

how does insulin bind and activate insulin receptors

Answer 17

approachs the space between the alpha subunits and the alpha subunits get closer to each other, which then causes the beta-subunits to approach each other and then the activation domains from each beta-subunit fits in the active site of the tyrosine kinase in the other beta-subunit causing the phosphorylation of tyrosin and giving the receptor its active conformation

Question 18

adaptor proteins are not

Answer 18

enzymes

Question 19

How is insulin signaling terminated

Answer 19

by the action of phosphatases
1- protein tyrosine phosphatase ( removing phosphoryl groups from insulin receptor and IRS)
2- Lipid phosphatase (PIP3 to PIP2)
3- protein serin phosphatase to deactivate Akt1

Question 20

what structural feature causes the dimerisation of EGF-receptors
what happens when EGF is absent

Answer 20

dimerisation arm from each subunit

the dimerisation arm is bound to its receptor preventing it from binding to the other receptor

Question 21

cross phsosphorylations in EGF-receptors

Answer 21

carboxyl-terminals rather than activation loops

Question 22

when is the kinase in egf-receptor activated

Answer 22

activated without phosphorylation

Question 23

GAPs

Answer 23

GTPase activating proteins (GAPs)

Question 24

In insulin and EGF-receptor mediated pathways

Answer 24

both act as tyrosin kinases

Question 25

pleckstrin homology domains

Answer 25

facilitate the interactions with lipid PIP3

Question 26

HER related to

Answer 26

EGFR stimulates overexpression even