Cell Signaling

Question 1

which ligand will need help to pass the membrane? where will receptor be found?

Answer 1

hydrophilic ligand

receptor on outside of cell (has to cross)

Question 2

which ligand will readily diffuse over the membrane? where will receptors be found?

Answer 2

Lipophilic

inside cell

i.e. steroid hormones

Question 3

what controls everything at the cellular level?

Answer 3

cell signaling

Question 4

what is the slow response?

Answer 4

gene expression changes

via MAP kinase

Question 5

what is fast response?

Answer 5

alterations in function of enzyme

generation of cyclic AMP

Question 6

extracellular signal binds to a specific receptor on target cells to initiate signal transduction

Answer 6

cell signaling

Question 7

3 types of signaling

Answer 7

autocrine
paracrine
endocrine

Question 8

autocrine

Answer 8

one cell feeds back on another

Question 9

endocrine

Answer 9

distal signaling

long lasting molecules, mostly steroid hormones

low turn over rate ,diffuse

Question 10

paracrine

Answer 10

fibroblasts below epithelium

localized signaling

Question 11

same ligand has different responses

Answer 11

i.e. acetylcholine

Question 12

steps in signal transduction (basic)

Answer 12

extracellular signal molecule binds to receptor protein

causes intracellular signal proteins to carry signal to effector proteins

Question 13

three types of receptors

Answer 13

ion channel coupled receptors
enzyme coupled receptors
g protein coupled receptors

Question 14

transmembrane component of G protein coupled receptor

Answer 14

anchors receptor

7 passes of membrane

Question 15

cytoplasmic loop of g protein coupled receptor

Answer 15

regulatory domain

not found in RTKs

Question 16

trimeric complex is inactive when…

Answer 16

it binds to cytoplasmic loop

becomes monomeric

Question 17

heterotrimeric G proteins

Answer 17

guanine nucleotide binding proteins with 3 subunits: alpha, beta, gamma

Question 18

what happens when G-proteins bind to cytoplasmic loop?

Answer 18

becomes inactive

is only monomeric g-alpha (beta and gamma are inactive)

Question 19

Active form of G-Protein …

Answer 19

occurs when it has a GTP

creates downstream conformation changes in enzymes (2nd messengers)

Question 20

2nd enzymes of the GpCR

Answer 20

adenyl cyclase

phospholipase C

Question 21

PLC makes

Answer 21

makes 2nd messengers

IP3 and DAG

Question 22

Adenyl Cyclase makes

Answer 22

makes 2nd messengers

cyclic AMP

Question 23

Phosphodiesterase

Answer 23

converts cyclic AMP to AMP

shuts down this signaling

Question 24

which 2nd messenger of GPCR is potentiating?

Answer 24

PLC

generates 2nd messenger

Question 25

which 2nd messenger of GPCR is attenuating?

Answer 25

PDE converts cyclic AMP to AMP to shut off signal (destroys second messneger)

Question 26

cAMP activates...

Answer 26

cAMP-dependent PKA

Question 27

cAMP-dependent Pka

Answer 27

4 subunits when cAMP binds it attaches to regulatory parts and pushes out activated units

Question 28

Cholera

Answer 28

failure to turn off signal (alpha subunit remains active) unable to hydrolyze GTP so PKA continually phosphorylates channel and water is sent out

Question 29

Ways to attenuate the signal of GPCR

Answer 29

1. hydrolyze GTP on G-Alpha subunit (dropping of hormone levels) 2. Remove signaling molecule 3. Endocytosis and endosome activity to completely sequester or destroy the receptor

Question 30

GRKs

Answer 30

kinase phosphorylates cytoplasmic domain to stop G-alpha phosphorylates receptors so arresting will bind to cap and prevent GTP from binding to G alpha

Question 31

arrestin protein

Answer 31

puts a cap on the third loop to prevent the activity of the receptor keeps alpha- g bound to GDP

Question 32

variations of G-Proteins

Answer 32

Gs Gi Gq

Question 33

Gs

Answer 33

stimulates adenyl cyclase

Question 34

Gi

Answer 34

inhibits adenyl cyclase

Question 35

Gq

Answer 35

activates PLC (instead of adenyl cyclase)

Question 36

phospholipase C makes what from PIP2

Answer 36

2 molecules, both activate PKC (and calcium) IP3 or Dag

Question 37

calcium signaling is which 2nd messenger system?

Answer 37

PLC to IP3 or DAG NOT tyrosine kinase

Question 38

PCK is activated by which second messenger(s)?

Answer 38

IP3 or DAG PLC pathway

Question 39

enzyme coupled receptors create

Answer 39

docking sites dimerize instead of activate complex

Question 40

what is the GEF in GPCR?

Answer 40

the receptor itself

Question 41

what is the GEF in tyrosine kinase?

Answer 41

SOS

Question 42

steps in tyr k.

Answer 42

1. Ligand binds to tyrosine monomer 2. tyrosine moonier aggregates --> dimerization 3. Autophosphorylation 4. SH2 domain of GRb2 binds to tyrosine kinase 5. SH3 of GRB 3 binds to SOS 6. SOS exchanges GTP for GDP from Ras 7. Ras binds to Raf

Question 43

Slow response of Ras-Raf example

Answer 43

Insulin signaling via gene transcription

Question 44

fast response of Ras-Raf pathway

Answer 44

Glut 4 Direct activation of enzymes that alter activity (already synthesized) G-PRotein coupled receptor

Question 45

Jak Sat

Answer 45

direct connection activate Jak, Stat goes to the nuclease

Question 46

Serine/Threonine

Answer 46

when Serine or Threonine is activated SMAD goes to nucleus