ch. 9 cell communication

Question 1

what two things are required for communication between cells?

Answer 1

a ligand and a receptor

Question 2

what is a ligand?

Answer 2

a signaling molecule

Question 3

what is a receptor?

Answer 3

a protein to which the ligand binds

Question 4

where are receptors located?

Answer 4

may be on the plasma membrane or within the cell

Question 5

what are the four basic mechanisms for cellular communication?

Answer 5

1. direct contact
2. paracrine signaling
3. endocrine signaling
4. synaptic signaling

Question 6

what is direct contact?

Answer 6

when ligand molecules on the surface of one cell are recognized by receptor molecules on an adjacent cell

Question 7

what is paracrine signaling?

Answer 7

when ligands released from a secretory cell bind to receptors on adjacent cells.

Question 8

what is endocrine signaling?

Answer 8

when special ligands called hormones are released from secretory cells and bind to receptors on or within cells throughout the body

Question 9

what is synaptic signaling?

Answer 9

when nerve cells release the signal ligands (neurotransmitters) which binds to receptors on nearby nerve or muscle cells.

Question 10

what happens when a ligand binds to a receptor?

Answer 10

the cell “responds” chemically

Question 11

what is signal transduction?

Answer 11

the series of chemical reactions that occur following the binding of a ligand to a receptor

Question 12

what can different cell types respond differently to?

Answer 12

the same signaling ligand

Question 13

what does signal transduction often involve?

Answer 13

activating or inactivating proteins

Question 14

what is kinase?

Answer 14

an enzyme that adds a phosphate to a protein, thus activating it

Question 15

what is phosphatase?

Answer 15

an enzyme that removes a phosphate from a protein, thus deactivating it

Question 16

what happens during protein phosphorylation?

Answer 16

a phosphate group (PO4-3 ) is added by a kinase to residues of the amino acids serine, threonine, and tyrosine. This can activate the protein.

Question 17

what are the two receptor locations?

Answer 17

cell surface and inside the cell

Question 18

what is an intracellular receptor?

Answer 18

a receptor located inside the cell

Question 19

what are the three classes of membrane receptors?

Answer 19

1. channel linked/gated receptors
2. enzymatic receptors
3. G protein-coupled receptors

Question 20

what are Channel linked or gated receptors?

Answer 20

class of membrane receptor where an ion channel opens in response to ligand binding

Question 21

when do receptors fall into the enzymatic class?

Answer 21

when the receptor is an enzyme that is activated by ligand binding

Question 22

what happens with G protein-coupled receptors?

Answer 22

a G-protein (protein bound to GTP) assists in transmitting the signal

Question 23

what is receptor tyrosine kinase?

Answer 23

an enzyme receptor

Question 24

what happens to the membrane bound receptor when signal ligand binds?

Answer 24

it is dimerized and autophosphorylated- activated receptor then adds a phosphate to tyrosine on a response protein

Question 25

what is an example of receptor tyrosine kinase signaling?

Answer 25

epidermal growth factor receptor

Question 26

what is a kinase cascade?

Answer 26

a series of protein kinases that phosphorylate each other in succession, amplifing the signal

Question 27

what is the purpose of a kinase cascade?

Answer 27

So, a few signal ligand molecules can elicit a large cell response

Question 28

what is a G protein?

Answer 28

protein bound to GTP

Question 29

what is a G protein coupled receptor?

Answer 29

receptors bound to G proteins

Question 30

_________ is a switch turned on by the ________.

Answer 30

G protein; G protein coupled receptor

Question 31

when a signal ligand binds receptor, what does G-protein activate?

Answer 31

an effector protein

Question 32

what can activate effector proteins?

Answer 32

G-protein coupled receptors

Question 33

what does the effector protein produce once activated?

Answer 33

a second messenger

Question 34

what does a second messenger do?

Answer 34

generates the cellular response

Question 35

what is an example of a common effector protein?

Answer 35

adenylyl cyclase

Question 36

what does adenylyl cyclase do?

Answer 36

converts ATP to cAMP, which then acts as a second messenger

Question 37

what is the function of a cyclic AMP?

Answer 37

serves as a second messenger to activate or inactivate proteins

Question 38

are steroid hormones polar or non-polar?

Answer 38

non-polar/lipid soluble

Question 39

why are steroid hormones nonpolar?

Answer 39

so that they can cross the plasma membrane to a steroid receptor

Question 40

what is the function of steroid hormones?

Answer 40

Usually regulate gene expression: an inhibitor blocks the steroid receptor from binding to DNA until the hormone is present.

Question 41

what are the three functional domains of a steroid receptor?

Answer 41

1. Hormone-binding domain
2. DNA binding domain
3. Domain that interacts with coactivators to affect gene expression (activating or deactivating transcription)

Question 42

what are autoinducers?

Answer 42

small molecules produced by bacteria that regulate gene expression

Question 43

what type of receptor are steroid hormones?

Answer 43

intracellular