Classification of Hormones by Chemical Structure Flashcards
hormones can be subdividied based on their chemical identities, what are the 3 categories?
- peptides
- steroids
- amino acid derivatives
Peptide Hormones
they are made up of amino acids
where are peptide hormones derived from?
they are cleaved during posttranslational modification.
-these smaller units are transported to the golgi apparatus for further modifications that activate the hormone and direct it to the correct location in the cell
how are they released?
such hormones are released by exocytosis after being packaged into vesicles
what is the consequence of peptide hormones having a charge?
they cannot pass through the plasma membrane, so they must bind to an extracellular receptor
- the peptide hormone is considred the first messenger
- it binds to the receptor and triggers the transmission of a second signal, konwn as the second messenger
other consequences of peptides
- they are short lived because they act through transient second messenger systems (its quicker to turn them on and off)
- because they are polar, they are water-soluble. this means that they can travel freely in the bloodstream and usually do not require carriers
Steroid Hormones
these hormones are derived from cholesterol and are produced primarily by the gonads and adrenal cortex
what is the consequence of steroid hormones being derived from nonpolar molecules?
they can easily cross the cell membrane
fun fact about their receptors
their receptors are usually intracellular (in the cytosol) or intranuclear. upon binding to a receptor, this complex can undergo conformational changed. the receptor can then bind directly to DNA, resulting in either increased or decreased transcription of particular genes, depending on the identity of the hormone.
what is the consequence of this previous process?
the effects of steroids are slower but longer-lived than peptide hormones
steroids and blood-transportation
steroid hormones are not water-soluble so they must be carried by proteins.
some of these are very specific and carry only one hormone
these steroid hormones are generally inactive while attached to a carrier protein and must dissociate form the carrier to function
Amino-Acid-Derivative Hormones
these are less common than the other hormones but they include epinephrine, norepinephrine, triiodothyronine and thyroxine
these hormones are usually derived from one or two aa’s, with additional modifications.
example
thryoid hormone: tyrosine with the addition of several iodine atoms
the chemistry of aa-hormones
catecholamines (epinephrine and norepinephrine): bind to G protein-coupled receptors
thyroid hormones bind intracellularly
