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Endocrine Physiology > Hormones, Hormone Receptors and Cell Signalling > Flashcards

Hormones, Hormone Receptors and Cell Signalling Flashcards

1
Q

Define hormones.

A

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

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2
Q

What is the action of hormone receptors?

A

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

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3
Q

What does changes in levels of second messengers cause?

A

Bring about cellular response to the hormone

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4
Q

What are the 3 types of hormones?

A

Peptide
Amine
Steroid

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5
Q

What are the 2 types of Amine hormones?

A

Catecholamines
Thyroid hormones

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6
Q

What are the three types of steroid hormones?

A

Androgens/estrogens/progestogens
Corticosteroids
Vit D

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7
Q

Do peptide hormones readily cross cell membranes?

A

No - polar molecules require receptors on surface of target cells

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8
Q

Where are peptide hormones synthesised?

A

Rough ER

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9
Q

Where are peptide hormones stored?

A

secretory vesicles

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10
Q

What is a characteristic of peptide hormones?

A

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

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11
Q

What is the main catecholamine hormone?

A

Epinephrine (produced in adrenal medulla)

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12
Q

Where is epinephrine synthesized?

A

Chromaffin cells

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13
Q

is epinephrine hydrophilic or hydrophobic?

A

Hydrophilic - must interact with receptors on target cell surface

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14
Q

What is epinephrine rapidly metabolized by?

A

Monoamine oxidase
COMT

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15
Q

What are the 2 types of thyroid hormones?

A

T3 - 7%
T4 - 93%

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16
Q

Where is T4 stored?

A

Outside the cell, not in vesicles

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17
Q

How are thyroid hormones transported?

A

require binding proteins as they are not water soluble

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18
Q

What is the binding affinity for thyroid hormones?

A

TBG > TBPA > Alb

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19
Q

What are all steroid hormones derived from?

A

Cholesterol

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20
Q

Where are steroidogenic enzymes located?

A

Mitochondria/smooth ER

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21
Q

When are steroid hormones released?

A

Immediately after synthesis - not stored

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22
Q

How do steroid hormones reach target cell?

A

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

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23
Q

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

A

Slower acting

24
Q

What are the 2 traits of hormone receptor binding?

A

Saturable and reversible

25
Q

What is binding affinity of a receptor defined by?

A

Equilibrium constant called KD
Lower KD = greater hormone binding affinity

26
Q

What does KD measure?

A

Receptor occupancy

27
Q

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

A

Straight line plot

28
Q

What is hormone sensitivity?

A

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

29
Q

What are Spare Receptors?

A

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

30
Q

What do steroid hormones need to do to become active?

A

Need to dimerize at P-box

31
Q

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

A

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

32
Q

How many domains do G protein coupled receptors have?

A

7 transmembrane domains
Plasma membrane receptor - catecholamines and peptides

33
Q

What does Ga bind to?

A

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

34
Q

What does Ga hydrolyse?

A

GTP to GDP

35
Q

What 3 things does Gi-alpha act on?

A

Ion channels
Inhibition of cAMP
Phospholipases

36
Q

What does Gs-alpha act on?

A

Increase cAMP

37
Q

What does Gq-alpha act on?

A

Increase DAG
IP3

38
Q

Define tyrosine kinase?

A

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

39
Q

How do most tyrosine kinase receptors become functional?

A

By dimerisation

40
Q

What do protein tyrosine phosphatases dephosphorylate?

A

Phosphotyrosine proteins

41
Q

What hormones use JAK-STAT signalling?

A

Growth hormone
Prolactin

42
Q

What do STATS regulate?

A

gene expression

43
Q

What is an example of integral tyrosine kinases?

A

Insulin

44
Q

What is an example of receptor associated tyrosine kinases?

A

Prolactin
Growth hormone

45
Q

Define second messengers.

A

Small diffusible (water or lipid soluble) molecules

46
Q

What are 3 different things do second messengers act on?

A

cAMP
Ca2+
Phospholipids

47
Q

Where is type II PKA found?

A

Membrane bound

48
Q

What does PKA regulate?

A

Gene expression working through cAMP Regulatory Binding Protein (CREB)

49
Q

What does Protein Kinase C mediate?

A

Effects of increasing cytosolic Ca2+

50
Q

What does protein kinase C require for maximal activity?

A

Ca2+ and DAG

51
Q

What is a PKC independent mechanism for Ca2+ signaling?

A

Calmodulin

52
Q

What hydrolyses PIP2?

A

Phospholipase C-beta

53
Q

What does the hydrolysis of PIP2 generate?

A

IP3 and DAG

53
Q

What does the hydrolysis of PIP2 generate?

A

IP3 and DAG

54
Q

What does the hydrolysis of PIP2 generate?

A

IP3 and DAG

Endocrine Physiology (12 decks)

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