Flashcards in Lecture 3 Deck (36):
what's beta amyloid and what problems can arise from it?
it's a transmembrane protein that helps with cell signaling, neuronal cell migration, synapse making, long term memory, and cell adhesion
-if there is abnormal cleavage of beta amyloid, we get an aggregation of A beta peptide in neuronal tissue that makes it resistant to proteolysis and causes ALZHEIMERS!
What are normal prion proteins PrP?
cell surface proteins in alpha helix form that are neuroprotective against ischemia and control circadian rhythms
serve to organize the myelin sheath
Creutzfeldt- jakob disease
normal prion protein gets converted to a variant that has the prion cross linked and resistant to proteolysis as a beta pleated sheet
the variation also INFECTS other PrP's to convert to the variant
-ataxia, dementia, paralysis, death
protein pumps definition plus example
transport proteins that require direct expenditure of energy to bring things into and out of the cell
EX) Na-K pump needs ATP to bring 3 molecules of Na out of the cell and allow 2 K into the cell to regulate intracellular volume
Carrier proteins transport things inside and out of the cell without the use of energy
inhibits the NA/K pump and increases the amount of Na in the cell. Because there is a lot of Na in the cell, there is a decrease in activity of NA/Ca pump that allows Na into the cell. This increases intracell Ca.
- used in CHF because more Ca in sarcoplasm allows more Ca increases the chronotropic affect of the heart
Example of secondary active transport
Na and glucose going down Na's concentration gradient (no energy)
BUT: To maintain gradient, Na coming in with glucose is transported by Na/k pump out to the extracellular space with DOES require energy (secondary active tx)
- multi-drug resistant transporter
- in kidney, intestine, liver. blood-brain barrier
What happens when MDR-1 is over expressed?
How do you fix it?
cancer can cause increase in MDR1 receptors and cause the cytotoxic drug (chemo) therapy to be transported out of the cell quickly, rendering the cell resistant to chemo
-target the RNA that's translated into MDR-1 and inhibit MDR1 translation or pharmacologic inhibitors
What's MDR-2 and what's a disease that arises from a defective MDR-2?
-transports conjugated bilirubin from hepatocytes to bile canaliculus to be excreated
-genetic disorder called Dubin-Johnson Syndrome which is asyptomatic but causes an increase in conjugated bilirubin in the plasma because of a mutation in MDR2 that causes it to be mislocated and have impaired translation- benign
-Expressed in the liver
- flippase (transfers phospholipids) of phosphatidylcholine where if flips it to outer canalicular membrane of hepatocytes so that they can be excreted in the bile
What's aquaporin 2?
water protein channels
aquaporin-2: expressed in renal collecting tubule cells and used for water reabsorption
Antidiuretic hormone (ADH)
causes translocation of aquaporin receptors to the plasma membrane of the collecting tubule cell
-this causes an increase in reabsorption of water across the apical domain of the tubule cells (therefore, anti diuretic and pressor)
results when both aquaforin 2 genes are inactivated by mutations; concentrated blood
What's the CFTR channel? what condition is associated with it?
CFTR is a Chloride channel and also regulates Na and biarb
Cystic fibrosis arises from CFTR probs- ductus deferens, lungs etc obstructed
proteins on cell surface can help with digestion. Give an example and list it's associated problem.
Lactase is a digestive enzyme that breaks down lactose so a decrease causes lactose intolerance with associated gas and bloating
What are linker proteins?
Linker proteins are used to link plasma membrane to cytoskeleton to help with STRUCTURAL SUPPORT.
Duchenne's muscular distrophy
- xlinked recessive disorder that causes problems with distrophin gene
-problem with linker proteins not binding the plasma membrane to the cytoskeleton and maintaining structural support of the cell
What are antigens exactly?
cellular identification tags, proteins
carbohydrates (oligosaccharides) attached to lipids and proteins
why do you feel dehydrated when you are drinking?
Because alcohol messes with your ability to use ADH and thus instead of retaining water, you pee it out and get dehydrated
a receptor for the cholera toxin
-allows cholera to enter the cell and increase cAMP
-increase in cAMP activates Cl- channel and gets Cl out of cell
-with Cl comes Na, Bicarb and water
what do proteins do with their charge?
they are negatively charged so they repel other negative charges
ex) keep rbc's apart
what are the four ways you can transport things across the plasmalemma?
what are the 5 distinct pathways of endocytosis?
non coated mediated endocytosis
caveolae mediated endocytosis
-non specific ingesting of fluid and solutes (macro)
-triggered by bacteria
-occurs in thyroid cells (take up throglobulin) and dentritic cells (for immune surveillance)
-at clatherin coated pits often on lipid rafts
-GTPase called dynamin required to pinch off vesicle with ligand-bound receptors in order to being it into the cell
-MAY OR MAY NOT be mediated by receptors that increase specificity of what's endocytosed.
-becomes uncoated once inside the cell so cell can use whatever was brought in
what are 2 examples of a clatherin-mediated endocytosis?
1) cholesterol in the form of LDL enters the cell thru a clatherin coated pit
2) Protein Hormones
What are located in coated pits?
cargo (ligand) receptors are bound to adaptin that is then bound to clathrin
How does salmonella typhimurium enter the cell?
What are two examples of non-coated mediated endocytosis?
what's an example of caveolae- mediated endocytosis?
Uses caveolin protein to bring things into the cell
simian virus 40 (was in polio vaccines) thought to cause tumor growth (no evidence)
ingestion of large particles
mediated by zipper mediated receptors
Depends on actin
fuse with lysosomes
What part of the plamalemma does cholera use to enter the cell?
what happens in familial hypercholesterolemia?
There is a mutation in LDL receptor being able to bind adaptin and the clathrin coated sheath which leads to an poor uptake of LDL into the receptor, increase in LDL in plasma and ultimately hypercholesterolemia