membranes Flashcards
what is the role of membranes?
to define boundaries and serve as permeable barriers
what is the fluid mosaic model?
envisions the membrane as a fluid belayer with a mosaic of associated fluids
what types of proteins are in membranes?
phospholipids, glycolipids and sterols
what is the lipid composition in membranes?
it varies greatly based on species and location
what are phospholipids composed of?
choline, phosphate, glycerol, two fatty acids - or choline, phosphate, sphingosine, one fatty acid
what are glycolipids composed of?
galactose, sphingosine, one fatty acid
is the lipid belayer symmetric?
it is asymmetric
how can the phospholipids move throughout the belayer?
rotation
lateral diffusion (moving throughout a single layer)
transverse diffusion (flip flopping between layers)
what proteins move phospholipids between layers and maintain lipid asymmetry?
translocases
what is FRAP?
fluorescence recovery after photobleaching (a method to tidy mobility of molecules in living cells)
what type of proteins do membranes have?
integral - have hydrophobic region
peripheral - on outside, associate with another membrane protein
lipid anchored proteins - bind fatty acids that get inserted into the membrane
what are the types of integral proteins?
monotopic
singlepass
multi pass
multisubunit
what are the types of lipid-anchored membrane proteins?
fatty acid or isoprenyl anchor
GPI anchor
what is the purpose of membrane proteins?
they detect and transmit electrical and chemical signals, mediate cell adhesion and cell cel commutation, and can move ions across celll membranes
can integral proteins cross membranes?
most are transmembrane, but monotopic proteins are only on one side (they irreversibly embed into a single face)
what do transmembrane proteins do?
move ions across membranes
where are peripheral membranes located?
bind to integral membrane proteins, weak and reversible
how are lipid anchored membrane proteins attached?
covalently bound to fatty acids or isoprenyl groups
what is an example of lipid anchored membrane protein?
trehalose
what happens to proteins and lipids outside of the membrane?
they are glycosylated
what is glycosylation?
the progress of a carbohydrate covalently attaching to a macromolecule
