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Final

study notes for lecture three: classifications of hormones


Department
Physiology
Course Code
PSL201Y1
Professor
Doug Mac Kay
Study Guide
Final

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LECTURE THREE: CLASSIFICATION OF HORMONES
((peptide/protein = 3+ AAs, steroid = cholesterol, amine hormones = single AA)
Ætheir properties are based largely on their composition
HORMONE CLASSIFICATIONS
Hormone
Synthesis, Packaging, Release
Processing
Other Considerations
peptide
hormone
synthesized like proteins
- preprohormone mRNA sequence is
transcribed with an ER signal sequence
- ribosomes translate the prohormone and in
the ER it undergoes modifications
- after ER prohormone goes into the golgi
where it undergoes more modifications and
packaging into a vesicle {part of the golgi}
- vesicle will be released from golgi into
extracellular space when needed
- made in advance
- stored in vesicles in the tissues/cells where
LW¶VPDGH
- released into the bloodstream via exocytosis
only when needed
- release is caused by an external stimulus
insulin
pre-pro-insulin in the ER, released
into golgi
released from the golgi as pro-
insulin after modification
cleaved to form active insulin and
non-active C-peptide
during exocytosis both insulin and
C-peptide are released into the
bloodstream in a 1:1 fashion
o most hormones, most common
o water soluble, dissolved in plasma =
GRHVQ¶WQHHGDFDUULHUWRFLUFXODWHWKHERG\
o short half life, easily degraded when
exposed to surroundings
o bind to plasma membrane receptors (they
proteins cannot enter the cell)
o C-peptide is not active like insulin
o because insulin has such a short half life
and is metabolized quickly, can measure
insulin levels by measuring levels of C-
peptide
steroid
hormone
- synthesized only from cholesterol
- made on demand
- released via simple diffusion into the cell
cholesterol is modified by enzymes
to make steroid hormones
adrenal cortex = aldosterone,
cortisol
ovary = estrogen
o water insoluble ± bound to carriers in the
blood
o long half life (compared to peptide
hormones)
o has cytoplasm/nucleus receptors because it
can move among cells
o because receptors are at nucleus, can
regulate gene expression
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