Hormones, Hormone Receptors and Cell Signalling

Question 1

Define hormones.

Answer 1

Chemical messengers carried in the bloodstream from site of synthesis to site of action

Question 2

What is the action of hormone receptors?

Answer 2

Detect first messenger, relay and translate it. Act as a second messenger

Question 3

What does changes in levels of second messengers cause?

Answer 3

Bring about cellular response to the hormone

Question 4

What are the 3 types of hormones?

Answer 4

Peptide
Amine
Steroid

Question 5

What are the 2 types of Amine hormones?

Answer 5

Catecholamines
Thyroid hormones

Question 6

What are the three types of steroid hormones?

Answer 6

Androgens/estrogens/progestogens
Corticosteroids
Vit D

Question 7

Do peptide hormones readily cross cell membranes?

Answer 7

No - polar molecules require receptors on surface of target cells

Question 8

Where are peptide hormones synthesised?

Answer 8

Rough ER

Question 9

Where are peptide hormones stored?

Answer 9

secretory vesicles

Question 10

What is a characteristic of peptide hormones?

Answer 10

It starts as Prohormone that needs to be cleaved into a hormone

Question 11

What is the main catecholamine hormone?

Answer 11

Epinephrine (produced in adrenal medulla)

Question 12

Where is epinephrine synthesized?

Answer 12

Chromaffin cells

Question 13

is epinephrine hydrophilic or hydrophobic?

Answer 13

Hydrophilic - must interact with receptors on target cell surface

Question 14

What is epinephrine rapidly metabolized by?

Answer 14

Monoamine oxidase
COMT

Question 15

What are the 2 types of thyroid hormones?

Answer 15

T3 - 7%
T4 - 93%

Question 16

Where is T4 stored?

Answer 16

Outside the cell, not in vesicles

Question 17

How are thyroid hormones transported?

Answer 17

require binding proteins as they are not water soluble

Question 18

What is the binding affinity for thyroid hormones?

Answer 18

TBG > TBPA > Alb

Question 19

What are all steroid hormones derived from?

Answer 19

Cholesterol

Question 20

Where are steroidogenic enzymes located?

Answer 20

Mitochondria/smooth ER

Question 21

When are steroid hormones released?

Answer 21

Immediately after synthesis - not stored

Question 22

How do steroid hormones reach target cell?

Answer 22

Via plasma transport proteins - extremely hydrophobic
Freely diffuse across plasma membrane

Question 23

Are they faster acting or slower acting compared to peptide hormones?

Answer 23

Slower acting

Question 24

What are the 2 traits of hormone receptor binding?

Answer 24

Saturable and reversible

Question 25

What is binding affinity of a receptor defined by?

Answer 25

Equilibrium constant called KD Lower KD = greater hormone binding affinity

Question 26

What does KD measure?

Answer 26

Receptor occupancy

Question 27

On a graph, what does the ratio of bound hormone to free hormone look like?

Answer 27

Straight line plot

Question 28

What is hormone sensitivity?

Answer 28

Hormone response to conc. -> sigmoidal curve Hormone that gives half maximal response

Question 29

What are Spare Receptors?

Answer 29

Maximal response without receptor saturation Lowers conc. of hormone needed to produce ED50 Increases cell sensitivity to hormone

Question 30

What do steroid hormones need to do to become active?

Answer 30

Need to dimerize at P-box

Question 31

What is the difference between steroid hormone and thyroid hormone MoA?

Answer 31

Steroid - intracellular receptor Thyroid - receptor already present in cell, bound to Vit A

Question 32

How many domains do G protein coupled receptors have?

Answer 32

7 transmembrane domains Plasma membrane receptor - catecholamines and peptides

Question 33

What does Ga bind to?

Answer 33

GDP in its inactive state -> activated by exchange of GDP for GTP

Question 34

What does Ga hydrolyse?

Answer 34

GTP to GDP

Question 35

What 3 things does Gi-alpha act on?

Answer 35

Ion channels Inhibition of cAMP Phospholipases

Question 36

What does Gs-alpha act on?

Answer 36

Increase cAMP

Question 37

What does Gq-alpha act on?

Answer 37

Increase DAG IP3

Question 38

Define tyrosine kinase?

Answer 38

Enzyme that adds a phosphate group to a tyrosine residue of a substrate protein

Question 39

How do most tyrosine kinase receptors become functional?

Answer 39

By dimerisation

Question 40

What do protein tyrosine phosphatases dephosphorylate?

Answer 40

Phosphotyrosine proteins

Question 41

What hormones use JAK-STAT signalling?

Answer 41

Growth hormone Prolactin

Question 42

What do STATS regulate?

Answer 42

gene expression

Question 43

What is an example of integral tyrosine kinases?

Answer 43

Insulin

Question 44

What is an example of receptor associated tyrosine kinases?

Answer 44

Prolactin Growth hormone

Question 45

Define second messengers.

Answer 45

Small diffusible (water or lipid soluble) molecules

Question 46

What are 3 different things do second messengers act on?

Answer 46

cAMP Ca2+ Phospholipids

Question 47

Where is type II PKA found?

Answer 47

Membrane bound

Question 48

What does PKA regulate?

Answer 48

Gene expression working through cAMP Regulatory Binding Protein (CREB)

Question 49

What does Protein Kinase C mediate?

Answer 49

Effects of increasing cytosolic Ca2+

Question 50

What does protein kinase C require for maximal activity?

Answer 50

Ca2+ and DAG

Question 51

What is a PKC independent mechanism for Ca2+ signaling?

Answer 51

Calmodulin

Question 52

What hydrolyses PIP2?

Answer 52

Phospholipase C-beta

Question 53

What does the hydrolysis of PIP2 generate?

Answer 53

IP3 and DAG

Question 53

What does the hydrolysis of PIP2 generate?

Answer 53

IP3 and DAG

Question 54

What does the hydrolysis of PIP2 generate?

Answer 54

IP3 and DAG