1.8 signal transduction/cell-cell signaling

Question 1

Cell signaling involves what 4 steps?

Answer 1

1. detection of stimulus
2. transfer of signal to cytoplasmic side
3. transmission of signal to effector molecules
4. response to stimulus

Question 2

A ______ is a protein that receives signals from outside/inside of the cell by binding specific ligands and initiating a signal cascade

Answer 2

receptor

Question 3

where are the 2 possible places cell receptors?

Answer 3

1. cell surface

2. inside the cell

Question 4

A _____ is a messenger that binds specifically to a receptor

Answer 4

ligand

Question 5

______ are small molecules that mediate the intracellular response to a stimulus

Answer 5

secondary messengers

Question 6

______ is the increase in the number of signaling molecules at each step of the cascade

Answer 6

signal amplification

Question 7

signaling pathways can be highly interconnected and participate in ______

Answer 7

cross-talk

Question 8

The same signal molecule can induce ______ in different target cells

Answer 8

different responses

Question 9

The default pathway for a cell is _____

Answer 9

death

Question 10

Which molecules diffuse through the cell membrane and bind to cytosolic or nuclear receptors?

Answer 10

Lipophilic signal molecules

Question 11

what are examples of lipophilic signal molecules?

Answer 11

steroid hormones

Question 12

what is another name for molecules that bind to receptors on the cells surface?

Answer 12

lipophobic signal molecules

Question 13

Do extracellular signals act slowly or rapidly?

Answer 13

BOTH, depends on the method

Question 14

Signaling pathways that usually effect change by ______ are fast (sec/mins)

Answer 14

de-phosphorylation

Question 15

Signaling pathways that usually effect change by ______ are slow (mins/hours)

Answer 15

transcriptional regulation

Question 16

An example of a fast signaling pathway is _____

Answer 16

secretion, metabolism (glycogen breakdown), change in cell mvmt

Question 17

An example of a slow signaling pathway is _____

Answer 17

increased cell growth or division (hormone expression)

Question 18

The steroid hormone _____ acts by activating a gene regulatory protein

Answer 18

cortisol

Question 19

What are the steps to how cortisol acts?

Answer 19

1. cortisol enters plasma membrane
2. conformational change activates intracellular receptor protein
3. receptor-cortisol complex moves into nucleus
4. complex binds to regulatory region of gene and activates or represses transcription

Question 20

______ use ATP to phosphorylate amino acid side chains in target proteins. This may increase or decrease the activity of an enzyme

Answer 20

Kinases

Question 21

________ hydrolyze phosphates off of residues

Answer 21

phosphatases

Question 22

Some common second messengers are _____ and _____

Answer 22

Ca, cAMP

Question 23

what are the 4 types of signaling?

Answer 23

1. endocrine: signaling over long distance
2. paracrine: signaling in close proximity
3. autocrine: self signaling
4. contact dependent: bw direct interaction between membrane molecules on 2 cells

Question 24

synaptic signaling is prominent in the _______ system

Answer 24

nervous

Question 25

name 5 examples of neurotransmitters

Answer 25

glutamate, glycine, GABA, biogenic amines, acetylcholine

Question 26

3 basic classes of cell-surface receptors

Answer 26

1. ion channel-linked 2. G-protein linked 3. enzyme-linked

Question 27

How does a receptor tyrosine kinase work?

Answer 27

1. kinase binds ligand 2. dimerization in the membrane 3. dimerization activates phosphorylation fxn of kinase 4. kinase enzyme autophosphorylates amino acids in its own intracellular domain 5. docking and adaptor proteins can then bind to the phosphorylated site 6. this activates the proteins which allows the signal to be further transmitted

Question 28

_____ have 7 membrane spanning helices

Answer 28

G-protein coupled receptors

Question 29

Process of G protein coupled receptor activation:

Answer 29

1. GPCR binds the ligand and then the G protein (GDP, a,b,y) 2. G protein is activated (GDP exchanged for GTP) 3. a-subunit with GTP dissociated from complex 4. a-subunit and By dimer can bind proteins to propagate the signal

Question 30

Ga has a ______ GTPase activity meaning that it has a built in on-off switch to keep it from running forever

Answer 30

slow

Question 31

G-protein activation steps (6)

Answer 31

1. hormone binding induces conformational change in receptor 2. activated receptor binds to Ga 3. causes conformational change in Ga which triggers dissociation of GDP 4. GTP binds to Ga, trigggers dissociation of Ga 5. hormone leaves receptor 6. Ga binds to effector 7. GTP --> GDP causes Ga to dissociate from effector and reassociate with Gby

Question 32

Cholera toxin is an A-B toxin causes ADP-ribosylation which converts the G-protein into a permanently active state, which results in ______-

Answer 32

increased levels of cAMP

Question 33

_______ are good drug targets becuase they regulate a variety of physiological processes and are at the cell surface

Answer 33

GPCR

Question 34

G-proteins can activate membrane bound enzymes that can ______

Answer 34

catalyze the synthesis of intracellular second messengers (ex: adenylyl cyclase --> cAMP)

Question 35

enzymes can be ______ by G-proteins

Answer 35

activated OR inhibited

Question 36

Rise in intracellular cAMP can activate _______ through ______

Answer 36

gene transcription, Protein Kinase A (PKA)

Question 37

Give the steps to cAMP activating gene transcription through PKA

Answer 37

1. signal molecule activates receptor 2. alpha subunit of G protein activates adenylyl cyclase 3. adenylyl cyclase catalyses transition of ATP to cAMP 4. cAMP activates PKA 5. PKA enters nucleus 6. PKA activates gene regulatory protein which binds to target gene & causes transcription

Question 38

Ex of how G-proteins can regulate ion channels?

Answer 38

G subunit can open K+ channels in cardiomyocyte when active

Question 39

Phospholipase C can be activated by G-protein signaling, give the steps:

Answer 39

1. Ach activates GPCR 2. alpha subunit activates Phospholipase C 3. Phospholipase C cleaves diaglycerol from IP3 4. IP3 opens Ca+ channel 5. Ca+ actovates PKC

Question 40

_____ and ____ pathways can intersect

Answer 40

PKC, PKA

Question 41

Nitric oxide can diffuse through ______, and does not interact with _____

Answer 41

biological membranes, receptors on target membranes

Question 42

NO directly regulates _______

Answer 42

target proteins

Question 43

NO can trigger relaxation in ________ and are known to be ______

Answer 43

smooth muscle cells, vasodiolators

Question 44

Steps of NO triggering smooth muscle relaxation:

Answer 44

1. Ach binds with receptor 2. catalyzes rxn of arginine --> NO 3. NO leaves cell and diffuses across membranes 4. NO binds to target protein 5. smooth muscle cell relaxes and causes vasodilation