Cell signalling

Question 1

____signalling may affect cells at a great distance, and the concentration of signal molecules is generally high

Answer 1

endocrine

Question 2

____signalling involves local mediators at low concentrations and a localized effect

Answer 2

paracrine

Question 3

____signalling involves a cell stimulating its own signalling pathway

Answer 3

autocrine

Question 4

___signalling involves direct contact between the two cells involved in signalling

Answer 4

Juxtracrine
contact-dependent contact between a cell surface signalling molecule and a receptor of another cell

Question 5

___signalling occurs when signal molecule moves directly between cytosols of two cells via bridge such as a gap junction or plays odesa at

Answer 5

direct

Question 6

If the signal molecule is permeable to the membrane the receptor will be_____. Where does this happen?

Answer 6

cytosolic.This happens in hormone signalling pathways

Question 7

____are utilized for signals soluble in the aqueous extracellular environment. In this situation, the signal does not actually enter the cell but instead transmitted into the cell by receptors

Answer 7

cell surface receptors

Question 8

What are the two major mediators of cell signalling?

Answer 8

protein phosphorylation
monomeric GTPases

Question 9

Kd=
Can be used to measure the ____
This is important as most receptors can bind to multiple signals

Answer 9

dissociation constant
the affinity of a signal(ligand) for a receptor

Question 10

G proteins require

Answer 10

GPCR(G-protein coupled receptor) and is mediated by heterotrimeric G protein (GTP-binding protein)

cell surface receptor

Question 11

What are GPCR’s

Answer 11

are seven-transmembrane receptors that activate heterotrimeric GTPases by exchanging the GDP for GTP in the alpha subunit. This causes the alpha subunit to separate from beta/gamma. Both can mediate downstream signalling but alpha is most predominantly

Question 12

The fight or flight response is a good example of

Answer 12

GPCR signalling

Question 13

Explain fight or flight

Answer 13

beta-adrenergic receptors( or glucagon) bind to epinephrine activating Gas which goes on to activate adenylyl cyclaces leading to production of cAMP

Question 14

What is cAMP?

Answer 14

is a secondary messenger but most of its effected are mediated through PKA(protein kinase A)

Question 15

Four types of cell surface receptors?

Answer 15

ION-Channel Ex.neurotransmitter gated ion channel
G-protein coupled receptors ex. Rhodopsin/Transducin
Enzyme-coupled ex.RTK
Nuclear receptor ex. steroid hormones

Question 16

GTP hydrolysis is?

Answer 16

GTP to GDP turning off

Question 17

Heterotrimeric G-proteins are ___different components. When alpha subunit is bound by GDP it associates with betaY and is___

Answer 17

3
alpha beta
Y

inactive

Question 18

GEF

Answer 18

guanine nucleotide-exchange factors

Question 19

GPCR acts as a ____when stimulated by its ligand which exchange GDP for GTP on the alpha subunit

Answer 19

GEF

Question 20

cAMP(cyclic adenosine monophosphate) activates a protein kinase called?

Answer 20

PKA(protein kinase A)

Question 21

Protein kinase A is composed for two___ and two___. Regulatory subunit inhibits the ___in the absence of cAMP. When cAMP attached to regulator genes it detaches from catalytic and now they are activated to phosphorlate target proteins

Answer 21

regulatory subunits and catalytic subunits
catalytic

Question 22

How can PKA regulate gene expression?

Answer 22

cAMP stimulates PKA which binds CREB to CRE by phosphorylation this activates transcription and CBP binds to CREB

Question 23

inositol-1,4,5,-trisphosphate and diacylgycerol are

Answer 23

secondary messengers

Question 24

Calmodulin

Answer 24

involved in Ca+ signalling and is a highly conserved single polypeptide with 4 high affinity Ca+ sites

10 fold in Ca+ leads to a 50 fold in calmodulin

binds to other proteins and activates
Calmodulin changes conformation when Ca2+ is bound and can regulate a number of different protein targets

Question 25

Receptor tyrosine kinases

Answer 25

Epidermal growth factor receptor (EGF) is not activate without P but once EGF binds to receptor it pulls another structure towards itself multimerization….then it trans-autophorylation each other

Question 26

WHen tyrosine kinase is activated it also activates ___indirectly

Answer 26

Ras by Sos

Question 27

MAP Kinase pathway?

Answer 27

MAP=mitogen activated protein
mitogen are growth signals

Three comments MAPK, MAPKK, MAPKKK

Ras and Raf are connected and activate MAPKKK

Ets and Jun are the MAPS-they activate transcription

Question 28

Insulin pathway?

Answer 28

Insulin goes on receptor(alpha) goes through PM(beta) this phosphorylats IRS-1( which is the MAP kinase pathway), IRS-1 activates P1 3 kinase which catalyze an addition of a phosphate to PIP2 into PIP3. PTEN can covert PIP# back into PIP2. Then PIP3 binds to Akt which can increase glycogen synthase activity and recruit GLUT4.