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29 Cards in this Set

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What are the 4 endocrine glands that make steroid hormones?
adrenal cortex, testes, ovaroes, placenta
what is the primary molecule used for steroid synthesis
cholesterol used comes from LDL
What is the RLS?
How do we get around it?
ability to enter the inner mitochondrial membrane from the Outer mito membrane. Use STAR (steroidogenic acute)regulatory protein
What mechanism affects/induces STAR activity?
cAMP dependent mechanism
How does the LDL get inside the membrane?
binds to receptors in plasma membrane, endocytosed, hydrolyzed with lysozyme and cholesterol released into the cell
Besides prod of hormone, what else happens to cholesterol once it enters the cell?
stored in the cell as cholesterol esters
The precursor for all the steroids?
Pregnenolone.
How does a cell become stimulated to make steroid hormones?
1) increase in movt of cholesterol from the mitochondria
2)uptake of plasma lipoproteins
3) hydrolsysis of stored cholesteroal ester
Do the steroidogenic cells store the hormones
NO
T/F: Rate of hormone synthesis in the adrenal cortex determines the rate of release/
True since there are no storage mechanisms
Enzyme resp for making cholesterol esters?
acyl CoA: cholesterol acyltransferase
Are steroid hormones lipid or water
lipid
What are the 3 proteins used to carry the hormones around in the blood?
SHBG, CBG, DBG
sex-hormone bg, corticosteroi-binding & Vitamin D
T/F Free cirulating proteins are NOT susceptible to excretion
False, they are susceptible to metabolism and excretion
What are the 3 advantages for a steroid hormone to be bound to protein/
1) allow the hormone to be transported in Conc. higher than their solubility
2) plasma reservoir of homones
3) protection from excretion or breakdown :)
What is the significance of albumin for the steroid hormones?
SH binds non-specifically and with low affinity
T/F unbound is in equilibrium with bound hormones?
TRUE
How do we get rid of steroid hormones?
we convert them to inactive metabolites?
Where is the main site for SH inactivation?
LIVER
What happens after inactivation?
Inactive metabolites are CONJUGATED to glucoronic nacid or sulfate and then EXCRETED by the kidney
How does conjugation help with the excretin of the SH?
1) increases solubility in water and decrease affinity for protein binding
What kind of receptors do the steroid hormones use?
The nuclear receptors they use function as LIGAND-ACTIVATED TRANSCRIPTION FACTORS
What does the nuclear localization signal of a Steroid hormone allow it to do?
1) allows the receptor to be in the nucleus or to be translocated to the nucleus when it it activated ( sometimes if unoccupied, some steroid receptors are in the cytoplasm while others hang out in the nucleus
When unoccupied, what does the steroid receptor bind to?
heat shock proteins
What happens when a steroid hormone binds to its receptor?
receptor unbinds from the HSP and then forms HOMODIMER with an occupied receptor of the same hormone. Then it binds to its target gene via HRE (specific DNA sequence) somewhere in the regulartory area
How does activation of gene transcription occur?
After hormone/receptor bind, COACTIVATOR PROTEINS are recruited. HAT activity turns on which decreases interactions b/t DNA and histones and allows transcrption to occur
How does negative regulation of gene transcrption work for the steroid hormones?
once dimers of the hormone and receptor are made, COREPRESSOR PROTEINS and HISTONE DEACTYLASES come.
What does HAT stand for and does it promote or inhibit transcription?
histone acyltransferase and it PROMOTES transcroption
What would a receptor antagonist do to a receptor?
it changes conformation of the receptor so that neither activator or repressor can bind