Actions Of Hormones - Cell Signalling Flashcards Preview

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Flashcards in Actions Of Hormones - Cell Signalling Deck (19):

Where are the receptors for lipophilic and hydrophilic hormones

Hydrophilic peptides and catecholamines
- via cell surface recep on outer PM
- amines - adrenaline and noradrenaline
- peptides - insulin, glucagon, ADH and GH

Lipophilic steroid and thyroid hormone
- via intracellular receptor
- glucocorticoids( cortisol), mineralcorticoids(aldosterone), oestrogens, progesterone, androgens(testosterone) and thyroid hormone


How do extracellular messengers bring about cell responses

Primarily by signal transduction


What su signal transduction

Process where incoming signals are conveyed into the cell where they are transformed into dictated cellular response

Diffenrt mechanisms dept on messenger and receptor type


How do hydrophillic hormones alter pre existing

Via seconday messenger systems


What do most hydrophilic hormones bind to

GPCR G protein coupled receptor


What are the two major secondary messenger pathways

Cyclic adenosine mono phosphate cAMP


What do both of the major secondary messenger pathways use

A G protein on the inner surface of the PM as an intermediary between receptor an effector proteins


What bind to G proteins when they are active or inactive

GTP when active and GDP when inactive


What dos San inactive G protein complex consist of

3 subunits - alpha beta and gamma
GDp binds to alpha


How does signal transduction occur with GPCR's

Hormone the first messenger binds to the receptor
Receptor then attaches to G protein - release of GDP form G protein complex
GTP then attaches to alpha subunit which activates alpha subunit
Alpha subunit dissociates from beta and gamma subunits and move to inner surface if PM until it reaches an effector protein Genzyme or ion channel)
The alpha unit links up with the effector protein and alters its activity


What are the two major G protein coupled effectors

These are both mem bound enzymes
1) adenylyl cyclase (cAMP)
2) phospholipase C (calcium)


What does adenylyl cyclase do

On the cytoplasmic side of PM it converts ATP to cAMP

cAMP activates a specific intracellular enzyme protein kinase A (PKA)

PKA phosphorylate a pre existing intracellular protein (threonine residues )


What happens with phospholipase c and Calcium

Binding of a hormone via a GPCR activates an enzyme phospholipase c

Plc break ps down PIP2 to yield DAG and IP3

DAG remains in the PM IP3 diffuses into cytosol

IP3 stimulate the release of calcium from ER

DAG regulates PKC ( PKC phosphorylates serine residues on specific intracellular proteins)


What kind of hormone is insulin

Peptide hormone.


How does insulin act

Binds to its cell surface receptor and activates 'autophosphorylation'

Insulin recep - tyrosine kinase


What dos phosphorylation of tyrosine kinase receptor lead to

Recruitment of glucose transporters to plasma membrane which increases glucose uptake to muscle and fat cells

Repress catabolic induce anabolic

Activates glycogen synthase glucose storage

Increases lipogenesis


What hormones can all cross the membrane and bind to intracellular receptors - cytoplasmic or nuclear

Steroid hormones, calcitriol and thyroid hormone


What happens at the hormone response element

The hormone receptor complex binds with DNA at a specific attachment site


How do hormones target specific cell types

Only target cells for particular hormone express receptors for binding with this hormone
Non target cells are not influenced