Biological membranes Flashcards
What are membrane functions
- barrier
- cellular organization
- transport
- signal transduction
- cell-cell communication
membrane lipids are ____which mean they have a hydrophobic and hydrophilic component.
amphipathic
What is the hydrophobic and hydrophilic region of glycerophospholipid
diacylgycerol; phosphorylated alcohol
What is the hydrophobic and hydrophilic region of sphingomyelin
ceramide; phosphorylcholine
what is the hydrophobic and hydrophilic region of glycosphingolipid
ceramide; sugar residues
what is the hydrophobic and hydrophilic region of cholesterol
hydrocarbon rings; OH group at carbon 3
Inner and outer leaflets of single membranes have different compositions:
One layer exposed to environment and one layer exposed to interior of cell.
What gets flipped out to exterior of cell during apoptosis and serves as a signal for phagocytosis
Phosphatidylserine; usually very little on outer leaflet, entirely internal
What does flipase do
move PE (phosphatidylehanolamine) and PS (phosphatylserine) from outer to cystolic leaflet
What does amount of membrane movement depend on
percentage of unsaturated fatty acids
What does floppase do
moves phospholipids from cystolic to outer leaflet (one used by phosphotidylserine)
What do scramblase’s do
moves lipids in either direction, toward equilibrium
What physical factors affect fluidity of membrane
- temperature
- pressure
- membrane potential
what chemical factors affect fluidity of membrane
- head group of phospholipid
- FA chain length
- FA unsaturation
- cholesterol
what indirect factors affect fluidity of membrane
- hormones
- adaptation to stress
- cell cycle
- cell differentiation
Unsaturated has more fluidity bc:
they cannot pack as tightly as saturated
% of saturated fats affects melting temp bc:
more long chain saturated fats inc melting temp due to packing
Lateral diffusion of cell-surface proteins is very fast:
- virus induced fusion
2. mixture of labeled proteins from the membranes in heterokaryon (hybrid cell)
Flourescence recovery after photobleaching is a techniqe to monitor lateral diffusion of lipids and proteins in membranes. How does it work?
- Shine light on it –> bleaches out flourescence
- Fourescence intensity goes very down
- Wait and it starts to recover as other still labeled monomers come to that region
- This shows that there is a lot of movement within our membranes.