Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
22 Cards in this Set
- Front
- Back
|
where do hormones come from and how do they travel
|
hormones are secreted by endocrine cells, they travel in the blood stream
|
|
|
describe steroid hormones
|
small, hydrophobic molecules (lipid soluble) related in structure to cholesterol that can cross the plasma membrane
|
|
|
Describe steroid hormones receptors (SHR)
|
intracellular proteins that function directly as transcription factors, they can activate or repress genes in the nucleus. The signal is direct, the hormone binds directly to the protein that will regulate changes in transcription
|
|
|
where do hormones come from and how do they travel
|
hormones are secreted by endocrine cells, they travel in the blood stream
|
|
|
describe steroid hormones
|
small, hydrophobic molecules (lipid soluble) related in structure to cholesterol that can cross the plasma membrane
|
|
|
Describe the general structure of SHRs
|
1. The N terminal region is the transcription activating domain
2. DNA binding domain 3. The c terminal is the hormone binding domain (c= capture) |
|
|
Describe the state of SHRs in the absence of hormone
|
they an inactive and complexed to an inhibitory protein
|
|
|
Describe steroid hormones receptors (SHR)
|
intracellular proteins that function directly as transcription factors, they can activate or repress genes in the nucleus. The signal is direct, the hormone binds directly to the protein that will regulate changes in transcription
|
|
|
Describe the general structure of SHRs
|
1. The N terminal region is the transcription activating domain
2. DNA binding domain 3. The c terminal is the hormone binding domain (c= capture) |
|
|
Describe the state of SHRs in the absence of hormone
|
they an inactive and complexed to an inhibitory protein
|
|
|
Describe what happens to and SHR when the hormone binds
|
The SHR changes conformatin and the inhibitory complex is released exposing the DNA binding domain. The SHR can now bind to its sequences within the promoters of the target genes and regulate transcription
|
|
|
How do peptide (water soluble) hormones initiate a signal
|
they cannot cross the plasma membrane so thyey initiate a signal cascade by binding to receptors at the cell surface
|
|
|
Describe the insulin receptor
|
an enzyme linked receptor (tyrosine kinase). In response to insuling binding the tyrosine kinase phosphorylates other proteins and changes their activities
|
|
|
What are the 6 steps of the G protein mechanism of action
|
1. hormone binds to G linked receptor
2. the active receptor activates the trimeric G protein 3. the G protein activates adenylyl cyclase 4. adenylyl cyclase makes cAMP from ATP 5. cAMP activates PKA (aka A kinase or cAMP dependent protein kinase A) 6. PKA phosphorylates target proteins |
|
|
Describe the structure of a G protein
|
3 subunits, alpha, beta, gamma.
|
|
|
describe the resting state of a g protein
|
alpha, beta, and gamma subunits are all bound, the alpha subunit has GDP bound
|
|
|
What happens to the G protein when it becomes active
|
the alpha subunit exchanges GDP for GTP and disassociates from the beta gamma units. The GTP bound alpha subunit activates adenylyl cyclase
|
|
|
WHat happens to the alpha subunit of a g protein after it turns on adenylyl cyclase
|
THe intrinsic GTPase activity hydrolyses the GTP to GDP and the alpha subunit disassociates from the adenylyl cylcase and regoins the beta/gamma subunit. This returns the protein to the rested state.
|
|
|
what enzyme is repsonsible for taking cAMP to AMP in order to "reset" the cell
|
cAMP phosphodiesterase
|
|
|
Describe the cascade that activates PEPCK
|
PKA binds to a DNA binding protein called CREB, CREB binds to the DNA elements in the promoter region of the PEPCK gene to activate transcription
|
|
|
How is it possible for a cell to respond to such small amounts of hormone in the blood?
|
the signal is amplified during the cascade
|
|
|
For a cell to remain responsive, a signal cascade pathway must be reversible. What are the 3 ways that a G protein system can be reversed?
|
1. GTPase activity of the trimeric G protein that is stimulated by adenylyl cyclase
2. hydrolysis of cAMP to AMP by cAMP phosphodiesterase 3. Ser/thr phosphatases dephosphorylate redsidues on target proteins that were phosphorylated by PKA |
