Cell Physiology - Cellular signaling - Lec. 3

Question 1

how do cells communicate with each other

Answer 1

receptors

Question 2

signal transduction

Answer 2

processing the received signal

Question 3

water-soluble signals

Answer 3

most common, binds to transmembrane proteins

Question 4

lipid-soluble signals

Answer 4

diffuse through membrane, bind to intracellular receptors, transduce signal via change in gene expression

Question 5

specificity

Answer 5

ability to receptor to only bind to a certain number of ligands (specific receptors, specific ligands)

Question 6

affinity

Answer 6

strength of ligand binding to receptor

Question 7

saturation

Answer 7

extent to which receptors are bound b ligand

Question 8

competition

Answer 8

presents of other ligands which compete for binding sites

Question 9

antagonist

Answer 9

no effect

Question 10

agonist

Answer 10

effect

Question 11

down regulation

Answer 11

lower # of target cell receptors, response to sustained high level of signal (- feedback), reduce cell response to frequent stimuli, mechanism is internalization

Question 12

up regulation

Answer 12

increase # of target cell receptors, response to sustained low levels of signal (+ feedback), increase in cell response to low stimulization, occurs through insertion of receptor containing vesicles into the cell membrane

Question 13

transduction of lipid-soluble signalling

Answer 13

response primary by nuclear receptors, causes gene expression.
1. diffusion across memebrane into cell
2. signals enter nucleus and bind
3. changes expression (mRNA) level of gene
4. mRNA abundance change effects change in protein leading to cellular response

Question 14

two phases of water-soluble transduction

Answer 14

1. binding of signal to receptor
2. signals generated by receptor

Question 15

protein kinases

Answer 15

enzymes that phosphorlate proteins

Question 16

receptor tryosine kinases

Answer 16

name of sites where phosphorylation occurs

Question 17

common mechanisims of water-soluble signalling

Answer 17

1. recpetoc that function as ion channels
2. receptors that function as enzymes
3. receptors that interact with cytoplasmic kinases (Janus Kinases)
4. receptors that interact with G-protein (g-protien coupled receptors)

Question 18

g- proteins - what they do

Answer 18

couple receptors with effector proteins to generate 2nd messenger

Question 19

g-protein sub groups

Answer 19

Gi - inhibits production of cyclicAMP
Gs - activates production of cyclicAMP
Gq - activates phospholipase C

Question 20

How g-protiens work in general

Answer 20

ligand bind changes affinity of alpha subunit to GTP, GTP/GDP exchange causes dissociation b/w alpha and beta-gamma subunit complex, activated alpha subunit binds to effector protein to initiate cellular response

Question 21

cAMP working and responses

Answer 21

activates cAMP-dependant protein kinases, PKA has many targets = elicit many responses

Question 22

cAMP synthesis

Answer 22

ATP is catalyzed by adenylyl cyclase

Question 23

cAMP breakdown

Answer 23

catalyzed by cAMP phosphodiesterase

Question 24

How do signals cause the cytosolic Ca2+ concentration to increase

Answer 24

1. activation of plasma memb.
2. opening of Ca2+ channels on the ER memb.
3. activate transport of Ca2+ out of the cell blocked by 2nd messenger.

Question 25

how does increased Ca2+ concentration elicit a cellular response

Answer 25

typically via binding to proteins and activating them

Question 26

Ways to stop signal transduction pathways

Answer 26

often occur at level of receptor activation
1. decrease conc. of signal (breakdown/uptake/diffusion)
2. change in receptor confomation (phosphorylation)
- changes signal binding affinity
- prevents further G-protein binding to receptor
3. receptor mediated endocytosis