2. cellular endocrinology Flashcards
what are the 3 classes of hormones
peptide- water soluble
amine- derivatives of tyrosine
steriod- lipid soluble (made from cholestrol)
features of water soluble hormones
catacholamines (adrenaline and noradrenaline)
made and stored until required
Don’t require a carrier protein for the blood
receptors are found on the surface of target cells
features of lipid soluble hormones
thyroid hormones (T3 and T4)
made from cholesterol as required and cannot be stored
need a carrier protein to be transported through the blood
receptors are found inside of target cells
what is the key enzyme for determining estrone?
aromatase
aromatase is a precursor for estrogen
little aromatase means you will produce more testosterone
how is target cell sensitivity regulated for hormones?
dependent on the number of receptors that are expressed in/on the cell
more receptors= more sensitive therefore producing a bigger response.
what is up regulation for target cell sensitivity?
increasing the synthesis or receptors. this occurs when there are low hormone levels for a long period of time. this will increase the sensitivity and therefore the response from the cell.
what is down regulation for target cell sensitivity?
when lots of hormone is being produced for long periods of time the cell will break down some of its receptors for that hormone. this decreases the cells sensitivity therefore reducing how much of a response it has.
what is signal amplification?
when one hormone molecule binding to its receptor triggers a cascade of second messengers which can end up producing a lot of product.
what is signal transduction?
process of converting a signal into a cellular response. the activation of a single type of receptor can activate multiple different intracellular pathways to cause several different effects.
what are the four mechanisms of signal transduction for peptide and catecholamine hormones
1- change in membrane potential
2- increase in calcium conc
3- phosphorylation of proteins
4- increase in gene transcription
what is the role of kinase molecules?
they phosphorylate other molecules which can result in increased or decreased activity
ionotropic vs metabotropic receptors
ionotropic- ion channel in the cell membrane that opens in response to neurotransmitter binding
metabotropic- receptor on cell membrane that initiates a number of metabolic steps to regulate cell function.
Features of a G protein coupled receptor
When the receptor is activated there is a conformational change- this means that the alpha subunit of the G protein is more likely to bind GTP.
when bound they can break off and interact with effector proteins in the membrane
what does Gs protein coupled receptor do in response to hormone binding to it
stimulates adenylyl cyclase which then activates cAMP which activates protein kinases involved in phosphorylation (these can activate or inhibit)
what does Gi protein coupled receptor do in response to hormone binding to it
inhibits adenylyl cyclase
results in:
decreased cAMP
decreased activation of protein kinase A
decreased protein phosphorylation
what enzyme do Gq protein coupled receptors activate and what does this result in?
activates phospholipase (PLC)
this creates the breakdown of PLC->IP3+DAG
DAG- activates protein kinase C which phosphorylates other proteins
IP3- binds to ligand gates calcium channels on endoplasmic reticulum which increases Ca levels in the cytoplasm.
what is the permissive effect (type of interaction between hormones)
one hormone is required for another hormone to be able to work to its full effect
What are thyroid hormones?
Thyroid hormones are lipid soluble and can cross cell membranes through diffusion.
What do deiodinase enzymes do?
Deiodinase enzymes convert T4 (inactive) into T3, the active form.
What happens when T3 binds to the thyroid hormone receptor?
When T3 binds to the thyroid hormone receptor, gene transcription is able to occur.
what is synergy (type of interaction between hormones)
when two hormones are working together the response is bigger then that of individuals responses.
What is the absorptive state?
An anabolic state characterized by high insulin levels, where molecules are built up.
What is the post absorptive state?
A catabolic state characterized by low insulin levels, where molecules are broken down.
What is an anorexigenic signal and what is a hormone that works as one?
A signal that promotes satiety and encourages you to stop food intake. leptin- its secretion increases after a meal to help you feel full.
