Chapter 5/Cell Signaling in Physiology

Question 1

Chemical messengers bind to

Answer 1

receptor

Question 2

Water-soluble messengers bind to receptors
located at the

Answer 2

plasma membrane

Question 3

Lipid-soluble messengers bind to

Answer 3

intracellular
receptors

Question 4

cells express different receptors

Answer 4

Specificity

Question 5

strength of ligand-receptor binding

Answer 5

Affinity

Question 6

Different cells can have different responses to same
ligand

Answer 6

Specificity: cells express different receptors.

Question 7

High affinity will bind at lower concentrations of
messenger

Answer 7

Affinity: strength of ligand-receptor binding

Question 8

the fraction of total binding sites
that are occupied

Answer 8

Saturation

Question 9

presence of multiple ligands able
to bind the same binding site

Answer 9

Competition

Question 10

blocks the action of a chemical
messenger

Answer 10

Antagonists

Question 11

activates receptors and triggers the cell’s
response

Answer 11

Agonist

Question 12

receptors are removed
(internalized) in response to intense exposure to chemical messengers.

Answer 12

Down-regulation

Question 13

number of receptors is
increased in response to low concentrations of
chemical messengers

Answer 13

Up-regulation

Question 14

Up-regulation & down-regulation

Answer 14

Receptor Regulation

Question 15

Can diffuse through the plasma membrane.
– Have intracellular receptors.
– Signal-receptor complexes bind directly to DNA
and alter gene expression.
– Slower response, but sustained response

Answer 15

Lipid-soluble messengers

Question 16

A broad range of receptors.
– Activate intracellular signaling cascades
– Can activate mediators that affect DNA
expression
– Faster response but less sustained.
– Involve first messengers and second messengers

Answer 16

Membrane-bound receptors

Question 17

Lipid-soluble messengers,
Membrane-bound receptors

Answer 17

Signal Transduction Pathways

Question 18

Activation of receptor results in open ion
channel.
* Opening of ligand gated ion channels increase
net diffusion of ions specific to channel.
* Often results in a change in the membrane
potential.
* Ex: Na+, K+, Ca2+

Answer 18

Ligand-Gated Ion Channels

Question 19

Some receptors have intrinsic

Answer 19

enzyme activity

Question 20

Most are protein kinases that phosphorylate
the amino acid tyrosine

Answer 20

Receptor tyrosine kinase

Question 21

transferring a phosphate
group from ATP

Answer 21

Phosphorylation

Question 22

Binding of messenger to
receptor activates
enzymatic portion of
receptor.
* This autophosphorylates
the receptor’s tyrosine
groups
* Docking proteins bind to
phosphorylated tyrosine
groups.
* Activate cell’s response

Answer 22

Events for receptors with tyrosine kinase activity

Question 23

These receptors do not have intrinsic kinase activity

Answer 23

Cytoplasmic Kinases

Question 24

Binding of ligand causes conformational
change in receptor that leads to activation of

Answer 24

JAK kinase

Question 25

-Family of 4 kinases, target different transcription factors. –Results in synthesis of new proteins.

Answer 25

Cytoplasmic Kinases

Question 26

Receptor with inactive protein complex bound to it.

Answer 26

G Proteins

Question 27

3 subunits: alpha, beta, gamma. – Alpha subunit can bind GDP and GTP. – Beta and gamma subunits anchor alpha subunit to the membrane

Answer 27

G-Proteins

Question 28

Binding of ligand to receptor changes conformation of the receptor. – Activated receptor increases the affinity of alpha subunit for GTP – Alpha subunit binds GTP and dissociates from the beta and gamma subunits. – Alpha subunit binds to effector protein in plasma membrane.

Answer 28

Steps

Question 29

G protein serves as a BLANK coupling a receptor to an ion channel or to an enzyme

Answer 29

SWITCH

Question 30

Can be stimulatory or inhibitory

Answer 30

G Protein-Coupled Receptors

Question 31

Most numerous type of receptor family, large variety of signaling pathways

Answer 31

G Protein-Coupled Receptors

Question 32

Adenylyl Cyclase

Answer 32

Second Messengers

Question 33

Activated by stimulatory G proteins – Catalyzes the conversion of ATP to cyclic AMP (cAMP) – cAMP acts as a second messenger

Answer 33

Adenylyl Cyclase

Question 34

cAMP action

Answer 34

Second Messengers

Question 35

cAMP action is terminated by cAMP BLANK

Answer 35

phosphodiesterase

Question 36

-Breaks down cAMP – Inhibition of cAMP phosphodiesterase prolongs actions of cAMP

Answer 36

Second Messengers

Question 37

cAMP binds to -PKA phosphorylates downstream targets

Answer 37

cAMP-dependent protein kinase (PKA

Question 38

Some G proteins inhibit Results in less generation of cAMP

Answer 38

adenylyl cyclase

Question 39

activated by Gq, catalyzes breakdown of a phospholipid (PIP2) -second messengers

Answer 39

Phospholipase C (PLC)

Question 40

- Diacylglycerol (DAG) – Inositol Triphosphate (IP3) – Both function as second messenger

Answer 40

Phospholipase C (PLC

Question 42

DAG activates

Answer 42

protein kinase C

Question 43

IP3 binds to ligand gated Ca2+ channels in

Answer 43

ER

Question 44

Ca2+ as

Answer 44

Secondary Messenger

Question 45

Ca2+ can be increased or decreased to elicit a cellular response

Answer 45

action potential

Question 46

Ca2+ is maintained at BLANK concentration in the cell

Answer 46

Low

Question 47

Electrochemical gradient favors diffusion into the cytosol via

Answer 47

Ca2+ channels

Question 48

Cell can be altered by influencing active transport systems of

Answer 48

Ca2+

Question 49

– Calmodulin – Troponin – Kinases

Answer 49

Ca2+ also acts by binding proteins and activating them

Question 50

Ca2+ as

Answer 50

Secondary Messenger

Question 51

Ca2+ also acts by

Answer 51

binding proteins and activating them

Question 52

Signal transduction pathways are eventually

Answer 52

shut off

Question 53

-Cessation of receptor activation -Decrease in concentration of first messenger

Answer 53

Cessation of Activity

Question 54

-Receptor become chemically altered – Phosphorylation of receptor prevents further G protein binding to the receptor – Plasma membrane receptors may be removed

Answer 54

Receptors can be inactivated in 3 ways

Question 55

Signal pathways do not exist in isolation, they occur simultaneously. * Many first messengers may simultaneously influence a cell. * “Cross-talk” can occur at one or more levels among signal transduction pathways.

Answer 55

Interactions of Signal Transduction Pathways

Question 56

Signal pathways do not exist in isolation, they occur BLANK

Answer 56

simultaneously

Question 57

Many BLANK messengers may simultaneously influence a cell.

Answer 57

first

Question 58

can occur at one or more levels among signal transduction pathways

Answer 58

Cross-talk