back exam 4 Flashcards
Fluid mosaic model
plasma membrane as sea with protein icebergs and lipid rafts floating in it
updated fluid mosaic model
more dynamic
icebergs not passive, rather specialized rafts with diverse roles especially in signalling
pure lipid mixtures can make non homologous patches
major component of cell membrane that helps determine fluidity and partitioning
cholesterol
2 global post translational modification
conformational changes docking site/recognition module for other proteins
where is the receipt of intercellular signall interpreted
transmembrane and cycosolic/nuclear receptors
5 steps of clathrin mediated endocytosis
nucleation at membrane
cargo selection - cargo molecules bind cargo receptors
coat assembly - adaptor molecule bind cargo receptors and recruit coat
vesicle scission - dynamin protein helps vesicle excise from membrane
coat disassembly - coat proteins fall off and are recycled
5 stages of phagocytosis
attraction - phagocyte attracted to microbe, chemotaxis?
adhesion- phagocyte must adhere to microbe, opsin helps
ingestion - engulfment of microbe by phagosome
digestion/killing of microbe
Elimination - digested fragments exocytosed form cell
what does the signal sequence look like and where is it located
N - terminal signal sequencee. forms and ampiphatic helix. individual amino acids can vary because the secondary structure is whats recognized. the ampipathic helix has hydrophobic residues clustered to one side
cell free experiment to determine if a protein can get to mitochondria
buy purified mitochondria
add c-terminal GFP tag to protein
incubate protein with mitochondria in two test tubes
add protesase to both test tubes and add detergent to ONE
use flourescent microscopy to view avenger
if its not imported you shouldnt see the protein in either tube
if it is imported you will only see it in the tube w/o detergent because it is protected from protease
2 functions of glycosylation
increase solubility
aid in spatial organization during folding
absence of enzyme that phosphorylates mannose on proteins destined for lysosomes; why are there lysosomal proteins in blood
lysosomal proteins without M6P will not make it into the lysosome and will instead go through the default secretory pathway into the blood
why is hydroxylation of proline residues in collagen alpha chains essential for maintaining the stability and integrity of collagen
it is needed for triple helix formation because OH facilliitates hydrogen bonding btwn aa residues
if protein is constitutively active when myristoylated, where is it when active and why would myristolation get it there
must be at the membrane, myristoylation is a lipid anchor that gets it to the membrane without attaching itself
nuclear import with NLS
GAP hydrolyzes GTP into GDP in the cytosol
GEF swaps GDP for GTP in the nuculeus on Ran
So ran GDP and importin are boht in higher concentrations in the cytosol, when importin binds to a NLS it moves down hill in to nucleus and so does Ran GDP
in nucleus, RanGDP become ranGTP which takes importin back releaseing cargo, this new complex goes downhill to cytosol
back in cytosol RanGTP is hydrolysed and dumps importin starting over again
another cell free mitochondria test
exposed to precurser protein on ice
signal sequence brings it into mitochondria
warm and add protease, mitochondria will protect and protein can be seen with prob or radiolabeling,
have detergent and protease group for control
