Mechanism of Hormone Action & Second Messengers

Question 1

What is the final outcome interaction of hormone and target cells? It depends on several factors…

Answer 1

hormone concentration
receptor number
affinity of hormone for receptor
duration of exposure to hormone
intracellular factors

Question 2

What is the threshold response?

Answer 2

minimal concentration of hormone needed to elicit a measurable response
- dose-response curve

Question 3

What is this curve called?

Answer 3

dose-response curve

Question 4

Responsiveness is expressed in a _______ relationship

Answer 4

dose-response

Question 5

The magnitude of the response correlated with _________

Answer 5

hormone concentration

Question 6

As hormone concentration increases, response [increases/decreases] then levels off

Answer 6

increases

Question 7

More receptors = [more/less] maximal response

Answer 7

more

Question 8

Higher affinity for hormone = [more/less] likely to get a response

Answer 8

more

Question 9

What is maximum response

Answer 9

a further increase in hormone will elicit no more response

Question 10

Define sensitivity

Answer 10

the concentration of hormone producing 50% of maximal response

Question 11

If more hormone is required to get 50% response, sensitivity [increases, decreases]

Answer 11

decreases

Question 12

In what two ways can sensitivity be changed?

Answer 12

change number of receptors
affinity of receptors

Question 13

What does down-regulating mean?

Answer 13

decreasing sensitivity
either the number or affinity of receptors decreases even when hormone concentrations are high*

Question 14

In down-regulation, there is a(n) [increase/decrease] of new receptors, and a(n) [increase/decrease] in degradation of existing receptors leading to [activation/inactivation] of receptors

Answer 14

decrease
increase
inactivation

Question 15

What is an example of down-regulation?

Answer 15

T3 down-regulates TRH receptors in anterior pituitary

Question 16

What does up-regulating mean?

Answer 16

increasing sensitivity
either the number or affinity of receptors increase

Question 17

In up-regulation, there is a(n) [increase/decrease] of new receptors, and a(n) [increase/decrease] in degradation of existing receptors leading to [activation/inactivation] of receptors

Answer 17

increase
decrease
activation

Question 18

What is an example of up-regulation?

Answer 18

GH increases its receptors in skeletal muscle and liver

Question 19

What is the general mechanism of hormone action?

Answer 19

hormone recognized and binds to membrane receptor
hormone receptor complex either coupled to signal-generating mechanism OR acts as one itself
generated signal (2nd messenger)

Question 20

When the hormone is recognized and binds to a membrane receptor, it forms a _______ complex

Answer 20

hormone-receptor complex

Question 21

Hormone-receptor complexes are what two forms?

Answer 21

coupled to a signal-generating mechanism
OR
acts as a signal-generating mechanism itself

Question 22

The generated signal (2nd messenger) affects intracellular process in what two ways?

Answer 22

alter activity
OR
alter concentration of functional/structural proteins

Question 23

Where are receptor systems?

Answer 23

cell membrane or within cell

Question 24

What are the types of hormone receptor systems?

Answer 24

classic cell membrane systems
catalytic cell membrane receptor systems
intracellular receptor systems

Question 25

How are classic cell membrane receptor systems classified?

Answer 25

classified according to membrane receptor structure OR second messenger system used - rapid response

Question 26

Do catalytic cell membrane receptor systems use a second messenger system? If not, what do they use?

Answer 26

NO enzyme system such as kinases - usually a rapid response

Question 27

What do intracellular receptor systems use?

Answer 27

cytoplasmic or nuclear receptors - SLOW

Question 28

T/F: G-proteins are coupling molecules use in almost all membrane receptor systems

Answer 28

TRUE

Question 29

What are G-proteins composed of?

Answer 29

heterotrimeric proteins (3 subunits)

Question 30

G-proteins are [activated/inactivated] when GTP is bound, [active/inactive] when GDP is bound

Answer 30

active inactive

Question 31

G-proteins can be ______ & _______

Answer 31

stimulatory inhibitory

Question 32

G-proteins are linked to one of two second messenger systems. What are they?

Answer 32

adenylyl cyclase w/ cAMP phospholipase C w/ IP3/Ca2+

Question 33

Adenylyl cyclase (enzyme) is linked with which second messenger?

Answer 33

cAMP

Question 34

Phospholipase C (enzyme) is linked with which second messenger?

Answer 34

IP3/Ca2+

Question 35

In the adenylyl cyclase system, GTP binds G protein and activates _____. The 2nd messenger, ______, is produced and activates ________. Intracellular proteins are phosphorylated by __________, causing physiologic actions

Answer 35

adenylyl cyclase cAMP protein kinase A protein kinase A

Question 36

In the phospholipase C system, GTP binds G protein and activates ______ which liberates _________ and _________ from ________. The second messenger, ______ causes [Na+/Ca2+/K+] release from ER or SR stores. _________ and ___________ activates __________, which phosphorylates proteins

Answer 36

phospholipase C DAG and IP3 IP2 IP3 Ca2+ Ca2+ and DAG protein kinase C

Question 37

What uses the catalytic receptor system?

Answer 37

ANP (anthill natriuretic peptide) NO

Question 38

What is the catalytic receptor system?

Answer 38

catalytic receptors on cell surface associated with enzymes on intracellular side

Question 39

What enzymes are part of the catalytic receptor systems?

Answer 39

guanylyl cyclase enzyme serine/threonine kinase enzymes receptor tyrosine kinases

Question 40

Define receptor tyrosine kinases

Answer 40

tyrosine kinase activity WITHIN the receptor itself has 3 domains when hormone binds, intracellular portion of receptor phosphorylates itself monomer and dimer types

Question 41

What does then extracellular domain of receptor tyrosine kinases do?

Answer 41

binds hormone

Question 42

What does then intracellular domain of receptor tyrosine kinases do?

Answer 42

where tyrosine kinase activity occurs

Question 43

What are the 3 domains of receptor tyrosine kinases?

Answer 43

extracellular domain transmembrane domain intracellular domain

Question 44

What is the monomer type of receptor tyrosine kinases?

Answer 44

receptor is going to dimerize AFTER hormone binds - tyrosine kinase is activated and phosphorylates tyrosine on itself

Question 45

What is the dimer type of receptor tyrosine kinases? Give two examples

Answer 45

receptor is already a dimer - insulin & IGF (insulin-like growth-factor 1)

Question 46

What are tyrosine kinase-associated receptors?

Answer 46

associate with other proteins that have tyrosine kinase activity - Janus kinase family

Question 47

T/F: The intracellular portion of tyrosine kinase-associated receptors cannot phosphorylate itself

Answer 47

TRUE

Question 48

Steroid hormones use _________ systems and use either _______ or _________

Answer 48

intracellular receptor cytosolic OR nuclear receptors

Question 49

Steroids initiate DNA [transcription/translation] and synthesis of new proteins

Answer 49

transcroption

Question 50

Steroid hormones diffuse across the membrane and binds receptor in _____ or _______

Answer 50

cytosol nucleus

Question 51

What are steroid-responsive elements?

Answer 51

specific DNA sequences in target genes once the steroid diffuses and binds to a receptor, the receptor undergoes a conformational change. The complex binds to these steroid-responsive elements

Question 52

After the complex binding to the steroid-responsive elements, the complex is now a ______ factor, and _____ is transcribed, translation occurs, new proteins, physiologic actions

Answer 52

transcription mRNA