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47 Cards in this Set
- Front
- Back
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What does a "peptide hormone mean" |
It is a collective name applied to peptides, polypeptides, and proteins that function as hormones. |
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What is another name for a peptide hormone? |
A "factor". It is an older term. |
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What are 2 examples of small peptides. Where are they from? |
1. TRH (Thyroid Releasing Hormone) - from hypothalamus. 2. ADH (Vasopressin) - from Posterior Pituitary. |
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Each amino acid weighs about how many daltons? When is this useful? |
They each weigh about 100 daltons, so its helpful for figuring out from a molecular weight it it is a small peptide or a protein. |
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What is the target and action of TRH (Thyroid releasing hormone)? |
The target is the anterior pituitary, and the action is the release of TSH (thyroid stimulating hormone). |
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What is the target and action of ADH (Vasopressin)? |
Target is the kidney and arterioles, the action is to increase water re-uptake and increase blood pressure. |
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How big does a peptide hormone have to be to be considered a protein? |
Greater than 40 amino acids, or about 5,000 kDa. (the ppt says kDa, but that sounds big to me. I think its really just Da). |
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What is an example of a protein hormone? |
Growth hormone. |
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Where does growth hormone come from, what does it act on, and what is its action? |
It comes from the anterior pituitary, targets the liver and bone, and causes an increase in metabolism and bone growth. |
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Briefly describe Growth Hormone Receptor |
It is a dimer, and once GH binds to one, it dimerizes and the other attaches as well, activating the intracellular portion. This one, like many others, happens to turn it into a kinase. |
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What is prolactin? |
It is a hormone similar to growth hormone that is made in the anterior pituitary and its action is to stimulate milk production. |
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What is the common fate for peptide hormones after binding to their receptors? |
They are often taken in and degraded in the lysosome. |
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How are peptide hormones transported in the blood? |
Small peptide hormones: they are at a low concentration and are soluble enough to be transported unbound. Large protein hormones (e.g. GH): must be carried by a soluble protein which is often similar to the protein receptor. (e.g. GH binding protein) |
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What main hormones does the hypothalamus release? Where is their destination and what is their purpose? |
TRH (Thyrotropin releasing hormone) GHRH (Growth hormone releasing hormone) Their destination is the anterior pituitary and they control the release of thyrotropin stimulating hormone and growth hormone respectively. |
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What main hormones does the anterior pituitary release? |
Thyrotropin stimulating hormone, corticotropin (ACTH), and growth hormone (GH) |
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What is the origin, destination and function of ACTH (corticotropin) |
Origin: anterior pituitary Destination: Adrenal cortex Function: Steroid synthesis |
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What is the origin, destination, and function of Thyrotropin stimulating hormone? |
Origin: anterior pituitary Destination: Thyroid gland Function: Controls the release of T3 and T4. |
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What main hormone does the posterior pituitary produce? Where is its destination and what is its purpose? |
Vasopressin (ADH): destination: Kidneys and blood vessels. Function: water retention and increased blood pressure. |
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What main hormone does the pancreas produce? Where is its destination and what is its function? |
Insulin. Destination: cells dependent on insulin. Function: Glucose uptake into cells by glusose transport proteins. |
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What is the "poster child" for protein hormones? |
Insulin. We know a lot about it and it will probably be on our test. |
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Briefly describe insulin. |
It is a protein with 2 chains joined by 3 disulfide bonds. |
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What is the disease associated with insulin and what happens to cells? |
It is associated with Diabetes. Cells can either starve or be poisoned as the metabolic pathways are messed up. |
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In what organ and cells are insulin, glucagon, and somatostatin made in? |
They are made in the pancreas. Insulin: islet cells (B cells) Glucagon: islet cells (A Cells) Somatostatin: islet cells ( D Cells) |
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How is insulin stored? |
It is stored in the beta cells of the pancreas. It is kept in vesicles, ready to be released when glucose blood levels are high. |
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How is insulin made, specifically, what form? |
It is made as preproinsulin. It contains the signal peptide, c-peptide, and the main insulin chain. |
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How long does the signal peptide and the c-peptide stay with the main insulin chain? |
The signal peptide is cleaved off after the insulin is moved into the RER when it is being synthesized. The c-peptide stays with the insulin in the vesicle and is co-secreted with insulin on a 1:1 basis. |
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Briefly describe the synthesis of insulin. |
After the gene is transcribed, the protein starts to be made (the signal strand is made first). The signal peptide causes the insulin to be transported into the RER and is then cleaved off. Then the insulin and the c-peptide are finished being made, transported to the golgi, cleaved from each other, and stored in vesicles together. |
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What is the "first pass" of insulin? |
After insulin is released, it goes straight to the liver, where half of it is consumed. This is the first pass. After this, it goes into circulation in the blood. |
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In order of lowest to highest, what is the strength of insulin activity of insulin, preproinsulin, and proinsulin? |
preproinsulin (weakest) proinsulin insulin (strongest) |
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Briefly describe insulin's receptor. |
It is a tetra peptide with 2 alpha and 2 beta subunits. When insulin binds, it causes a conformational shift that activates a tyrosine kinase activity on the inside of the membrane. |
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What are the 4 general steps of insulin causing the uptake of glucose? |
1. Insulin binds 2. Glut 4 is translocated to membrane 3. Glut 4 is fused with the membrane 4. Glucose comes in. |
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What are the general ideas behind the TSH (thyroid stimulating hormone) receptor? |
It is a homo dimer that when it is bound to TSH, a kinase activity that allows it to phosphorylate things. |
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Briefly describe G coupled proteins and mention where a cascade would begin. |
After a beta-effector binds to the receptor in the membrane, the alpha subunit will exchange its GDP for a GTP and move down the membrane (away from the beta and gamma subunits) to activate adenylyl cyclase. Once acenylyl cyclase is activated, it makes cAMP and the cascade begins there. |
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What does the "G" in G-protein binding stand for? |
Guanisine binding. |
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What is the difference between a Gs and a Gi protein? |
A Gs is a stimulatory protein that stimulates adenylyl cyclase. Gi is an inhibitory g-protein that inhibits adenylyl cyclase. |
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True/False: cAMP production must be closely regulated as it is hard to get rid of. |
False: It is easily and quickly broken down by PDE to prevent any unwanted reactions. |
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Give a few key points of cascade mechanisms. |
It is the idea that one molecule (e.g. hormone) can stimulate a huge response, resulting in the increase to about 10,000 molecules towards the end. Protein Kinase A (PKA) is a major player and is activated by cAMP. The response is amplified. |
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Briefly describe the regulation of PKA. |
PKA has 2 catalytic subunits, that when inactivated, are bound to 2 regulatory subunits. cAMP can come and bind to the regulatory subunits (4 available sites), causing them to release the catalytic subunits and expose the active sites. When cAMP leaves, the catalytic and regulatory subunits will join back together. |
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What hormones use the calcium/calmodulin mechanism? |
Primarily vasopressin (ADH) and thyroid releasing hormone (TRH) |
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Which is a more powerful cascade, the calcium/calmodulin mechanism or the PKA signaling pathway? |
The calcium/calmodulin is more powerful because it results in the formation of 2 cascades, not just one. |
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Briefly describe the calcium/calmodulin mechanism. |
Once the G-protein is activated by the receptor, it goes and activates Phospholipase C-beta. This then degrades PIP2 into DAG and inositol-1,4,5-P3. DAG goes and activates PKC (protein kinase c) which phosphorylates a target protein and starts a cascade. Inositol goes and opens Ca channels on the ER, causing Ca to flow into the cytoplasm, activating a Ca/CaM protein kinase, which phosphorylates another target protein and starts a second cascade. The Ca also aids in the first cascade. |
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In general, how are peptide hormones synthesized and stored? |
They are synthesized as prehormones or preprohormones and stored in membrane bound granules. |
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Are peptide hormones typically polar or nonpolar? |
They are relatively polar. |
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Can peptide hormones be administered orally? |
No. They cannot. |
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How do peptide hormones typically travel in the blood? |
typically unbound. |
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What type of receptors do peptide hormones have? |
Usually cell membrane receptors. |
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What pathways do peptide hormones usually trigger? |
They usually use G-protein receptors and PKA or Calcium DAG mediated pathways. |
