Topic 1: Biomembranes Flashcards
(39 cards)
4 Functions of biomembranes
- compartmentalization
- a selective permeability barrier
- scaffold for biochemical activities
- respond to external signals
amphiphilic meaning
hydrophobic tail and hydrophilic head
What is the fluid mosaic model
it describes the biological membrane as a fluid bilayer with embedded proteins and how the asymmetry of the structure fits its functionality
The three major classes of membrane lipids
- phosphoglycerides
- sphingolipids
- sterols
What is special about Phosphoglycerides?
- most abundant class of lipids
- the head groups can differ
structure of phosphoglycerides
hydrophilic head has a
- phosphate
- different amino acids (head group?)
hydrophobic tail has
- 2 fatty acid tails
- glycerol
how are head groups linked to the glyerol
by phosphodiesterbonds
what are the 3 head groups most used in our class and their charge?
- phosophatidylethanolamine
- phosophatidylserine (-)
- phosophatidylcholine
What are the functions of the head groups?
- affect the interaction of other macromolecules in the bilayer
- have signalling functions
what are phosphoinositides?
they are bind to the cytosol leaflet and after the pathway it turns into messenger from calcium release and other intracellular stuff
What’s the pathway of phosphoinositides to IP3
1) phosphatidylinositol (PI) turns into PI 4-phosphate (PIP) by PI-4 kinase
2) then PI-4 phosphate turns into PI 4,5 biphosphate (PIP2) by PIP-5 kinase
3) PI 4,5 biphosphate to inositol 1,4,5 triphosphate (IP3) by phospholipase C and gives released from the cytosolic leaflet and DAG remains
sphingolipids
they are derivatives of sphingosine with a fatty acid tail
what is sphingomylien?
they are sphingolipids with a phosphocholine head group
what counts as phospholipids?
sphingomyelin and phosphoglycerides
what is a glycolipid?
sphingolipids that have single sugar or branched oligosaccharides as the head groups
where are glycolipids found?
the exoplasmic side of the plasma membrane
what is the function of glycolipids?
- protect the cell form harsh conditions
- helps in cell adhesion
- changes the electric field of the membrane
- changes the concentration of ions at the membrane surface
- Promotes protein folding and mediates binding of protein to chaperones
- Makes glycoproteins more resistant to proteolytic digestion
structure of sterols
have hydrophilic OH attached to 4 fused hydrophobic carbon rings
what are unsaturated lipids
hydrocarbon tail that contains a double bond (kinked)
what are saturated lipids
hydrocarbon tail that contains a no double bonds
what makes a fluid like membrane
short and unsaturated acyl chains
what makes a gel like membrane
long and saturated acyl chains
explain lipid rafts
lipid drafts
- cholesterol and sphingolipids cluster together in the membrane microdomains
- lipid drafts are more order and resistant to extraction with non ionic detergents
- cholesterol makes the bilayer less fluid and permeable to water soluble molecules
what is the hydrophobic effect
it is a tendency for hydrophobic (non polar molecules) to cluster together to limit the amount of surface area that has to interact with the hydrophilic parts.
-IT IS NOT AN ATTRACTIVE FORCE
