Cell Bio: Plasma Membrane Flashcards
3 main receptor types; which is intracell?
- Receptor tyrosine kinase
- G- protein coupled receptor
- Steroid receptor (intracell in cytosol)
Which RTK (receptor tyrosine kinase) have single pass transmembrane protein? (1)
PDGF
Which two RTK have 4 subunits? Which portion is extracellular?
Insulin and IGF-1 receptors–> 2 alpha are bound by disulfide bonds and bind extracell ligand; 2 beta subunits are intracell and have tyrosine kinase activity
What is the first step in activity of RTKs?
autophosphorylation
What protein on clathrin do the receptor proteins (the ones that extend extracellulary) bind to?
adaptin
What protein helps to pinch off a vesicle in reeptor-mediated endocytosis?
dynamin
What happens to LDL receptors once they are endocytoses with the help of clathrin?
- Clathrin uncoats from vesicle
- contents delivered to lysosome
- Portion of endosome with LDL receptor buds off an RETURNS TO PLASMA MEMBRANE
What is defective in a mutant LDL receptor that causes familial hypercholesterolemia?
cant bind to adaptin–> LDL receptor works fine, but cannot do endocytosis, b/c cant bind to clathrin
Kinases and phospharylases are different how?
Kinase–> phosphorylate using ATP
Phosphorylase–> phoshphorylates using inorganic phosphate in an ATP-independent fashion
What enzyme removes phosphate groups?
Phosphatate
What cofactor do carboxylases need?
Biotin–> these add a carbon group
What does Na+/K+ ATPase do?
puts 3 Na+ out of the cell in exchange for 2 K+ coming in
What are drugs that inhibit Na+/K+ ATPase? Why useful in heart dz?
Cardiac glycosides (digoxin and digitoxin)–> inhibit the Na+/K+ ATPase directly. Increased Na+ in the cell decreases the activity of a Na+/Ca++ exchanger that pumps Ca out of the cell–> increased Ca++ = increased myocardial contractility
Two most abundant substances in plasma membrane
- proteins
2. phospholipids
How does ouabain inhibit Na/K ATPase?
binds to K+ binding site
