Lecture 7

Question 1

what are most cell signals?

Answer 1

extracellular signaling molecules: any moleculle that can transmit a signal (proteins, hormones, ions, gases)

Question 2

receptor

Answer 2

binds a signaling molecule, can also be inside cell

Question 3

ligand

Answer 3

receptors bind to ligands, another word for extracellular signaling molecule that binds to receptors
specific ligand-receptor interaction

Question 4

intracellular signaling molecules

Answer 4

anything that transmits a signal inside the cell

Question 5

secondary messenger

Answer 5

subtype of intracellular signaling molecule, any NON-PROTEIN

Question 6

effector proteins

Answer 6

recieve signal, example: transcriptional regulator

Question 7

2 types of SHORT DISTANCE extracellular signaling molecules

Answer 7

1. contact dependant - membrane bound signal molecule (example - niches for stem cells)
2. paracrine - one cell secretes signaling molecule, only travels short distance (example - morphogens)

Question 8

how are paracrine signals regulated to onlly travel a short distance?

Answer 8

1. internalized
2. degraded
3. limited diffusion
4. receptor expression of other cells

Question 9

autocrine signaling

Answer 9

secretes a signal that can interact with secreting cell

Question 10

long distance signaling

Answer 10

1. synaptic - cell bodies far apart but axon membrane is very close to target membrane
2. endocrine cell - signal travels through bloodstream, only cells expressing receptor recieve signal

Question 11

what are the 2 classes of receptor/ligand interactions

Answer 11

1. cell-surface receptors - usually hydrophobic signaling molecule, large TM domain, molecule does not enter
2. intracellular receptors - small signal molecule (sometimes with carrier protein) crosses membrane and interacts with target protein inside cell

Question 12

can phosphorylation change charge? is it reversible?

Answer 12

1. yes
2. yes

Question 13

G protein activated when is bound and inactive when is bound

Answer 13

1. GTP
2. GDP

Question 14

what is GEF and what does it do

Answer 14

guanine nucleotide exchange factor
exchange GDP for GTP therefore activating the protein

Question 15

what is GAP and what does it do

Answer 15

GTPase-activating protein
hydrolyze GTP to GDP inactivating G protein

Question 16

what does polyubiquination indicate to the cell

Answer 16

signals protein for degredation

Question 17

what does multi ubiquitination do

Answer 17

endocytosis

Question 18

what does ubiquitination USUALLY do

Answer 18

turns signaling off

Question 19

how do inhibitor proteins work with transcriptional regulators

Answer 19

bind transcriptional regulator, but when phosphorylated it can’t inhibit. signal signals for kinase to release regulator

Question 20

all or none switch

Answer 20

even when signal is gone, output/response continues

Question 21

what does an oscilating output indicate about the signaling pathway

Answer 21

negative feedback

Question 22

5 types of negatative feedback

Answer 22

1. short delay
2. long delay
3. receptor inactivation
4. receptor sequestration
5. receptor destruction

Question 23

can acetylcholine trigger different responses in different cells?

Answer 23

yes! can have same receptor but different downstream effects/effectors or different receptors triggering different downstream signaling

Question 24

how can cells be specific in a complex of cellular environment?

Answer 24

1. signaling complexes
2. coincidence detectors

Question 25

what are scaffold proteins?

Answer 25

binds to several components in signaling pathway bringing them close together and in order (proteins can bind before or after signal)

Question 26

what are phosphoinositides/PIPs?

Answer 26

membrane lipids with head group that can be phosphorylated in different positions help scaffold signaling proteins

Question 27

what do SH3 domains bind to

Answer 27

proline-rich sequences

Question 28

what do SH2 and PTB domains bind to

Answer 28

phosphorylated tyrosines

Question 29

PH domains bind to

Answer 29

phosphoionositides (PIPs)

Question 30

if a scaffold protein doesn't require phosphorylation to bind intracellular signal proteins, what domains would it have in these binding regions?

Answer 30

SH3 and proline rich domains

Question 31

if a scaffold protein DOES require phosphorylation to bind intracellular signal proteins, what domains would it have in these binding regions?

Answer 31

SH2 and PTB domains

Question 32

what is a coincidence detector?

Answer 32

intermediate proteins that must be activated by 2 different signals, usually by 2 different kinases, to initiate further downstream signaling