membrane structure Flashcards
what is it called when lipids are not soluble in water
hydrophobic
where can bilayer be found?
in membrane and organelles.
X In spingolipids, what causes the linkage for the tail and head?
amino acids via an amide bond (N-c=o)
X in glycolipids what is attached to the amino acid
carbohydrates
X what is the importance of sphingolipids
importance in disease like diabetes, cancer, microbial infections
X what is the structural purpse of sphingolipids?
general protection from harmful environmental factors, adhesion for extracellular proteins (cell adhesions link cells to the extracellular matrix and to each other), signal transmission and cell recognition.
X what are the 3 classes of lipids
- Phosphoglycerides (e.g., phosphatidylcholine)
- Sphingolipids (e.g., sphingomyelin)
- Sterols (e.g., cholesterol)
what are amphipathic molecules
molecules with both polar and non-polar regions.
X what are phosphoglycerides composed of
polar head group, two hydrophobic fatty acid tails, 3 glycerol hydroxyl groups attaches the head to tails,
X how many carbons long are the two fatty acids in phosphoglycerides
16-18 carbons long (c-h)
X glycerol acts as a platform for attachment for head to tails. the two oxygens bond as the place for attachment, in which type of bond?
ester bond (c-o-c)
X what is the third oxygen bonded to in glycerol?
phosphate= po4
X the head of phosphoglycerides are polar. how does this occur?
phosphate -ve charge, choline +ve charge = both strongly ionic.
X the fatty acid tails are non-polar what does this mean?
no charges on fatty acids.
X the polar head group is composed of a phosphate group linked to another molecule like choline (alcohol) what would this be called?
phosphatidyl choline.
X what is an examples of phosphoglycerides?
phosphatidylcholine
X where do sphingolipids occur?
outer part of membrane (exoplasmic membrane)
X where can sphingolipids be found?
CNS and display biological function
X what is sphingolipids backbone made from?
sphingosine (head part)
X sphingomyelin is an example of sphingolipids. what does the structure look like?
sphingomyelin has a polar phosphoryl-choline head.
X what does the structure of sterols look like?
single polar HYDROPHILIC HEAD (OH), attached to steroid ring (carbon rings), and a short non-polar tail (hydrophobic attracted to tails of phospholipids in centre of membrane).
X what percentage of nerve cell membranes are sterols?
25%
what does lipid composition determine?
determines fluidity and mobility of the cell membrane.
what does membrane fluidity refer to?
the easiness of things moving in and out of the lipid bilayer of the cell membrane
what 3 factors affect fluidity of membrane?
- saturated and unsaturated fatty acids
- temperature
- cholesterol
what is the effect of saturated fatty acids on formation of the fatty acid tail?
no double bond–> straight formation of fatty acid
what is the effect of UNsaturated fatty acids on formation of the fatty acid tail?
double bonds–> disruptive formation
what is the effect of longer tail lengths?
increased IM (intermolecular) interactions and rigidity (bent, change shape)
what is the effect of shorter tail length?
less interactions between tails and fluidity
what is the effect of low temperature on fluidity?
low temperature = low energy = low fluidity
what is the effect of warm temperature on fluidity?
warm temperature = more energy = more distance= high fluidity (allows membrane to adapt its shape)
what does cholesterol molecules in the membrane act as?
temperature buffer
in cold temperatures what does cholesterol do to the phospholipids and how does this affect fluidity?
cholesterol keeps phospholipids apart = increase membrane fluidity
in warm temperatures what does cholesterol do to the phospholipids and how does this affect fluidity?
cholesterol binds lipids tighter together = decrease membrane fluidity
what does increased phospholipid tail length mean for fluidity?
decreased membrane fluidity
what does increased temperature mean for membrane fluidity?
increased membrane fluidity
at high temperatures how does cholesterol affect membrane fluidity?
decreases fluidity
at low temperatures how does cholesterol affect membrane fluidity?
increases membrane fluidity
how does an increase in saturated fatty acid (no double bond) content affect membrane fluidity?
decrease membrane fluidity (increases packing between phsopholipids, straight formation stronger rigid )
what does the subdomain of the plasma membrane contain?
variety of proteins (cell signalling), lipid raft (contains high concentrations of cholesterol and glycosphingolipids)
how are lipid rafts positioned in the plasma membraned?
more ordered and tightly packed than the surrounding bilayer. they float freely in the membrane bilayer
what is the difference between the plasma membrane and the bilayer membrane?
plasma membrane encloses the organelles (membrane for the organelles) and bilayer membrane is what encloses the whole cell.
what’s the difference between normal bilayer and plasma membrane?
plasma membrane is high in cholesterol and sphingolipids therefore more compact and solid than normal bilayer
what is the role of the plasma membrane?
compartmentalises (divides into categories) functions in the cell membrane like transmembrane proteins, carbs for signal recognition, G protein receptors
X what are the types of membrane proteins? (5)
peripheral proteins, integral proteins, membrane bound proteins, transport proteins, glycoproteins.
X what are the 2 types of transport proteins?
channel proteins, carrier proteins
what are the functions of protein membrane?
JET RAT
junctions- serve to connect and join 2 cells together
enzymes- fixing (joining to active site)to membranes localises metabolic pathways
transport- responsible for facilitated diffusion and active transport
recognition- may function as markers for cellular identification
anchorage- attachment points for cytoskeleton and extracellular matrix
transduction-function as receptors for peptide hormones
X how does the movement of phospholipids happen?
laterally (side to side)
X what are the 2 characteristics of movement of phospholipids laterally?
- occurs frequently
- requires little energy
X how else does movement occur of phospholipids?
across membrane TRANSVERSE (FLIP FLOP)
X WHAT ARE THE CHARACTERISTICS OF FLIP FLOP TRANSVERSE MOVEMENT ?
SLOW MOVEMENT WITHOUT CATALYST, flipase catalyst (outer to inner), floppose (inner to outer), SCRAMBLASE catalyst flip flop at the same time, energy provided by ATP
what are 3 characteristics of liposomes which carry drugs in the body (hydrophobic and hydrophilic drugs)?
- bilayer of amphipathic molecules
- hydrophobic outer layer with hydrophilic core
- vary in size
what are 3 characteristics of micelle to transports drugs (hydrophobic drugs)?
- monolayer of amphipathic molecules
- hydrophilic outer layer with hydrophobic core
- smaller in size normally 2-10nm
what type of drugs do micelles deliver ?
hydrophobic drugs like antibiotics, chemotherapeutic agents, anti-migraine formulations
are liposomes natural or synthetic?
either
where are hydrophobic drugs placed placed in the membrane in liposomes?
its placed in the lipid bilayer (in-between the two sets of tails)
where are hydrophilic drugs contained in liposomes?
hydrophilic: in the aqueous core
what can liposomes be used in?
chemotherapeutic agents such as doxorubicin and cytarabine for treating ovarian cancer, AIDS
