Principles of Hormone Action Flashcards
What are the main steroid hormones?
Sex hormones + progesterone
Androgens
Cortisol
Aldosterone
What are amino acid hormones usually derived from?
Tyrosine and tryptophan
What type of hormones are catecholamines and thyroid hormones?
Amino acid derivative hormones
What are eicosanoids derived from?
Arachidonic acid
Why do eicosanoids no stray far from their production site?
They degrade easily
What are the main functions of eicosanoids?
Roles in inflammation, blood pressure and clotting.
What type of hormone is prostaglandin?
Eicosanoid
How are peptide hormones stored?
Stored in vesicles until stimuli signals their release into the blood.
What are the two classes of receptor?
Intracellular receptors
Cell surface receptors
What are intracellular receptors the primary receptor for?
Steroid hormones as the can diffuse across the phospholipid membrane
How do cell surface receptors work?
Perform signal transduction. Converting extracellular signals into intracellular signals.
What are the three categories of of cell surface receptors?
- G protein coupled receptors
- Enzyme linked receptors
- Ion channel linked receptors
How do ion channel linked receptors work?
- Ligand binds to a receptor.
- Changes the structure of the protein channel, allowing ions to pass through into the cell.
- Ions activate enzymes and voltage sensitive channels producing a response.
Which cell surface receptor is heterotrimeric?
G protein coupled receptors
What is meant by heterotrimeric?
Means the receptor has three different subunits
How does the g protein coupled receptor process work?
- Ligand binds to GPCR
- GPCR changes shape
- alpha subunits exchanges GDP for GTP
- alpha subunit dissociates and regulates a target protein.
- alpha subunits activates it’s target protein, the target protein can then send a signal via a second messenger.
- GTP is hydrolysed to GDP allowing the cycle to repeat.
What does RGS stand for?
Regulation of g protein signalling
What does RGS do?
RGS accelerates hydrolysis of GTP allowing a new ligand to bind faster.
How do enzyme linked receptors work?
Enzyme linked receptors are cell surface receptors with intracellular domains that associate with an enzyme when activated.
How do cell surface receptors typically work?
Via a second messenger, involving protein kinases and cyclic AMP.
What is down regulation of receptors?
Occurs when a receptor is chronically exposed to a ligand. This results in ligand-induced desensitization or internalisation of the receptor.
What is upregulation of receptors?
Cells are super-sensitized due to repeated exposure of an antagonistic drug, or prolonged absence of the ligand.
What controls regulation of melatonin?
Melatonin secretion is related to the length of the night.
What is increased production of melatonin in winter a sign of?
Seasonally affective disorder
