Flashcards in Cell biology II Deck (54):
What is the contribution, in percentage, of proteins to the plasmalemma?
Beta-amyloid precursor protein is important in what (five) cellular processes?
1) Neuronal migration during development2) Synaptic formation and repair3) Cell signaling4) Long-term potentiation5) Cell adhesion
What is the causative molecule involved in Creutzfeld-Jakob disease?
A variant prion protein
What is the normal prion protein (PrP) involved in, normally?
Cell surface, glycosylated GPI anchor within lipid rafts
What does the variant prion protein do in Creutzfeld-Jakob disease?
Crosslinks filaments that are resistant to proteolysis and accelerates formation of other variants of the same form
Normal prion proteins are implicated in what cellular processes?
1) Neuroprotective against ischemia2) Control Circadian rhythms3) Serve to organize myelin sheath
What do carrier proteins do?
Transport one or two chemicals in one direction, or two molecules in opposite directions without energy expenditure
What are protein pumps?
Transport proteins requiring the direct expenditure of energy
What does the Na/K pump do?
1) Cleaves ATP to transport three Na out of the cell and two K into the cell2) Functions to regulate intracellular volume
What does digoxin do?
Partially inhibits Na/K pump, leading to decreased activity of Ca/Na transporter. Result is an increase in sarcoplasmic [Ca]
What are multidrug resistant transporters (MDRs)?
Subfamily of primary transporter proteins that are ATPases
Where is MDR-1 expressed?
1) Kidney2) Intestine3) Liver4) BBB
What does overexpression of MDR cause?
Causes some cancer cells to become resistant to cytotoxic drugs
How is MDR-1 overexpression combatted pharmacologically?
1) RNA interference2) Pharmacological inhibitors
What does MDR-2 transport?
Which transporter is responsible for direct bilirubin?
Which protein is defective in Dubin-Johnson Syndrome?
A defect in MDR-2 leads to what disease?
Where is MDR-3 expressed?
What is the function of MDR-3?
Flippase of phosphatidylcholine - flips it to the the outer canalicular membrane of hepatocytes so that it may be excreted into bile
What are aquaporins?
Protein channels for water
What are the protein channels for water called?
How many isoforms of aquaporins are there?
Aquaporin-2 is expressed by what type of cell?
Renal collecting tubule cells
Renal collecting tubule cells express what protein channel, specifically?
What induces translocation of aquaporin receptors to the plasma membrane of collecting tubule cells?
What does the translocation of aquaporin receptors to the plasma membrane of collecting tubule cells do to water reabsorption across their apical domain?
Nephrogenic diabetes insipidus results from mutation of both ________ genes
Mutations in both genes of aquaporin-2 results in what disease?
Nephrogenic diabetes insipidus
What kind of channel is CFTR?
What does CFTR regulate in addition to chloride?
Na and HCO3-
Na and HCO3- is regulated by what channel?
Where are glycolipids found, exclusively?
Noncytosolic lipid monolayer (also found in some intracellular membranes)
What glycolipid serves as a receptor for cholera toxin?
Ganglioside Gm1 serves as a receptor what what toxin?
What does cholera toxin do once it binds to ganglioside Gm1 receptor?
Ramps up synthesis of cAMP, leading to efflux of Na and water into intestinal lumen
Carbohydrates in the plasmalemma have what charge?
What are the five pathways for endocytosis?
1) Macropinocytosis2) Clathrin-mediated endocytosis3) Non-coated-mediated endocytosis4) Caveolae-mediated endocytosis (Simian virus 40)5) Phagocytosis
Where does macropinocytosis occur?
Thyroid cells as they take up thyroglobulin and dendritic cells for immune surveillance
Macropinocytosis relies on what type of cytoskeletal element?
Is macropinocytosis specific or nonspecific for its substrate?
What molecule is required to pinch off the vesicle in clathrin-mediated endocytosis?
Can clathrin-mediated endocytosis be mediated by receptors?
What are two examples of receptor-mediated clathrin-mediated endocytosis?
1) Cholesterol (in LDL form) 2) Protein hormones
Where are cargo receptors located in clathrin-mediated endocytosis?
What molecule associates with the intracellular portion of the cargo receptor in clathrin-mediated endocytosis?
What is the role of adaptin in clathrin-mediated endocytosis?
Associates with the intracellular portion of the cargo receptor
What condition occurs when there is a decrease or defect in LDL receptors?
Recycling of synaptic vesicles is performed by what type of endocytosis?
Cholera and Shiga toxins enter the cell via what endocytotic mechanism?
Is phagocytosis receptor-mediated?
Yes, generally (zipper-mediated)
Phagocytosis is dependent on what type of cytoskeletal component?
Does phagocytosis require clathrin?