Biomembrane Flashcards
what is a lipid bilayer?
provides the basic structure for all cell membranes, double-layered sheets with hydrophobic tails sandwiched between the hydrophilic heads
what is amphiphilic?
have a hydrophobic and hydrophilic end
polar molecules dissolve _____ in water
well
what happens when you add nonpolar molecules in water?
it cannot form favorable interactions with water so it forces adjacent water molecules to reorganize into ice-like cage structures, increasing free energy
what is a micelle?
cone-shaped molecules with their hydrophobic tail inwards
why does a phospholipid bilayer close to form a sealed compartment?
edges of the bilayer are exposed to water so it curls up into itself to avoid water exposure which is energetically unfavorable
what is the difference between cytosolic and exoplasmic?
exoplasmic is outside of the cell and cytosolic is inside the cell
how does endocytosis/exocytosis work?
lipid bilayer pinches in and encloses the exoplasmic/endoplasmic portion within the lumen
what are the 3 main categories of lipids?
phosphoglycerides, sphingolipids, sterols
what are phosphoglycerides?
form lipid bilayer, most abundant, two fatty acid tails, phosphate group, head group, glycerol
what are sphingolipids?
forms lipid bilayer, long fatty acid chain attached to sphingosine via amide linkage, different head group,
what are the 4 major lipids in mammalian plasma membrane?
phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, phosphatidylinositol
what are sterols?
4 ring hydrocarbon, abundant in mammalian cells but not in prokaryotes, -OH group interacts with water. usually embedded in membrane to give structure but cant form full lipid membrane
how are sterols represented in animals?
cholesterol
how are sterols represented in fungi?
ergoterol
how are sterols represented in plants?
stigmasterol
why cant sterols form a lipid bilayer on their own?
too hydrophobic
can lipids move laterally?
yes
how do you test to see if lipids move laterally?
FRAP (fluorescence recovery after photobleaching)
what is FRAP?
you label a certain section with fluorescence then bleach it. wait and see if it stays bleached or not. used to see for lipid movement
what is photoactivation?
add fluorescence to an area and see if it speads
when do lipids flip-flop?
almost never. usually laterally or rotation
what is thicker unsaturated double bonds or saturated bonds?
saturated bonds
what are lipid rafts?
microdomain of less-fluid lipids distributed among more fluid lipids, lipids not evenly distributed, also contains receptor proteins and signaling proteins
