Ch 16: Cell signaling

Question 1

what is signal transduction

Answer 1

the process of converting 1 type of signal to another

Question 2

How are signal molecules detected by a target cell?

Answer 2

Target cell’s have cell surface or intracellular receptors that the signal molecules bind to and release the signal

Question 3

Describe Long distance, wide distribution cell communication

Answer 3

signal travels through the bloodstream, only cells with correct receptors will respond

Question 5

Describe short distance, local distribution

Answer 5

Signal affects nearby cells in local area

Question 6

What is autocrine signaling?

Answer 6

Cells release a ligand that will bind to receptors on itself or neighboring identical cells

Question 7

Long Distance, cell specific

Answer 7

signal travels a long way (like through the neuron) to reach one specific cell at the end

Question 8

Cell Cell specific

Answer 8

Cells touch each other directly and the signal passes through surface proteins

Question 9

What type of signal molecules are for cell-surface receptors?

Answer 9

large, polar/hydrophilic signal molecules

Question 10

What type of signal molecules are for intracellular receptors?

Answer 10

small, non-polar/hydrophobic signal molecules

Question 11

Agonist vs. Antagonist

Answer 11

Agonist: activates pathway, mimics signal
Antagonist: blocks pathway, binds and prevents correct signal from binding

Question 12

Positive vs. Negative Feedback

Answer 12

Positive: response strengthens and encourages original signal for more
Negative: response inhibits or reduces original signal to keep things balanced

Question 13

T/F: the same signal molecule can produce different response in different types of target cells

Answer 13

True

Question 14

What is combinatorial control

Answer 14

combination of different signaling pathways necessary to make a distinct response

Question 15

which receptor would cause a very rapid enzyme response?

Answer 15

ligand binding to an intracellular (pass the membrane) receptor directly activates an intracellular enzyme to make a rapid response

Question 16

what type of cells make NO (nitric oxide)?

Answer 16

endothelial cells

Question 17

does NO bind to cell surface or intracellular receptors

Answer 17

intracellular receptors, easily diffuses through membrane

Question 18

which enzyme does NO bind to and activate? what does that trigger the enzyme to do?

Answer 18

Guanylyl Cylase, converts GTP –> cGMP. blood vessels dilate and lowers blood pressure

Question 19

NO binds to _____ , which makes _______, to _______ blood vessels

Answer 19

guanylyl cyclase, cGMP, dilate

Question 20

what enzyme breaks down cGMP into GMP

Answer 20

phosphodiesterase

Question 21

what does NO break down into

Answer 21

nitrates/nitrites

Question 22

which signaling molecule binding can activate NO synthase (NOS) in endothelial cells?

Answer 22

acetylcholine

Question 23

Function of Sildenafil

Answer 23

SIldenafil aka viagra prevents phosphodiesterase from breaking down cGMP so that the signal lasts longer

Question 24

Cell Surface Receptor: Ion- Channeled Coupled Receptor

Answer 24

ligand binds to ion channel receptor, opens channel for ions, changes membrane potential

Question 25

Cell Surface Receptor: GPCR

Answer 25

ligand binds to GPCR receptor, activates G protein by swapping GDP --> GTP, G protein goes on to activate other enzymes or ion channels

Question 26

Cell Surface Receptor: Enzyme Coupled Receptors

Answer 26

1. ligand binds to receptor, causing 2 receptors to dimerize 2. protein kinase phosphorylates receptor ON 3. activated receptor will phosphorylate other target proteins to trigger various pathways 4. protein phosphatase dephosporylates enzyme-linked receptor, OFF

Question 27

How does a G protein activate ion (K+) channel

Answer 27

1. acetylcholine binds to GPCR, activates G protein 2. Alpha subunit binds to ion channel, channel opens 3. Dephosphorylation of GTP --> GDP inactivates G protein 4. channel closes, trimeric G protein reunites

Question 28

an activated G protein will bind to ________ to make cAMP from ATP.

Answer 28

adenylyl cyclase

Question 29

What is the ligand that binds to the G protein that causes the pathway to make cAMP.

Answer 29

adrenaline

Question 30

what molecule does caffeine block?

Answer 30

caffeine blocks cAMP phosphodiesterase (PDE) from degrading cAMP into AMP. causes cAMP levels to stay elevated in the cell for longer periods

Question 31

IP3, DAG, and Ca2+ are examples of

Answer 31

second messenger molecules

Question 32

explain the steps of of how PKC is activated

Answer 32

1. ligand binds to GPCR and activates G protein 2. Alpha subunit binds and activates phospholipase C 3. Phospholipase C will cleave inositol phospholipid into IP3 and DAG 4. IP3 binds to Ca2+ channel at ER to open 5. Ca2+ molecules will exit Ca2+ channel and bind to PKC 6. DAG also binds to PKC (protein kinase C) to activate

Question 33

what is the most common helper protein Ca2_ binds to?

Answer 33

calmodulin

Question 34

what is calmodulin's major target protein?

Answer 34

CaM-kinase

Question 35

explain the steps of how Ca2+ --> Calmodulin

Answer 35

Ca2+ from ER lumen binds to calmodulin, calmodulin activates CaM-kinase, CaM kinase will phosphorylate other proteins

Question 36

explain how RTK (receptor tyrosine kinases is activated

Answer 36

1. ligand binds to receptor RTK 2. RTK forms dimer (pair up) 3. each half of RTK phosphorylates the other (autophosphorylation) 4. phosphorylated RTK recruits other proteins to phosphorylate them and activate them to start a signaling cascade inside the cell

Question 37

What is Ras, what does it cause, explain how it works using RTK and how that starts MAP kinase cascade

Answer 37

Ras is a GTP binding protein, causes cancerous tumors. 1. ligand binds to RTK 2. RTK activates via autophosphorylation 3. RasGEF binds to activated TRK,, activates Ras by swapping GDP to GTP 4. Activated Ras protein starts MAP kinase cascade (tells cells to grow or divide mitosis)

Question 38

T/F: cells require a negative signal to stay alive

Answer 38

false, positive

Question 39

How does an active Akt protein prevent apoptosis

Answer 39

1. survival signal binds to RTK 2. Activates PI3K-AKt pathway 3 Act gets activated 4. Active Akt promotes cell survival by inhibiting proteins that trigger apoptosis

Question 40

What molecule can Akt activate to stimulate cell growth, and is also hyperactive in cancer cells

Answer 40

Tor

Question 41

What anticancer drug targets Tor

Answer 41

rapamycin, stops it from stimulating too much growth that causes cancer

Question 42

What protein causes apoptosis

Answer 42

Bad protein, releasing its partner Bcl2 inhibits apoptosis