Membrane Structure and Properties Membrane Lipids Flashcards
General Functions of Membranes
- Compartmentalization (organells - membrane bound comparments - delegate function - increase effecancy)
- Defines a cell’s boundary (plasma membrane - seprates from exteriror)
- Selective Permeability(Regulates, mediates transport) (allows what gets in and what gets out of cell)
- Generates electrochemical gradients (change in voltage due to ion gradent often maintained by ATPases - energy investment - also directs cellular processes)
- Sensor of external stimuli (also internal, cell signaling pathways, adapt to changes in enviorment via receptors)
- Mediates adhesion (protiens - cell cell junctions)
Plasma Membrane
is a __ barrer that __
Protects _
is a fluid __
all cells have
Selective barrier that defines the cell
Protects the interior of the cell from the external environment
is a fluid mozahc - has to be cterin degree - membrain fluidity - for protines to function
Plasma Membrane has
glycome - suggar coat
membrane protines - transport, receptors, etc.
lipids, two layers - non polar in core
membraines are ___ assemblies of __
non covalant
of amipathic (or ampifillic) lipids and protines
Interactions of lipid bilayer
h bonds - polar interacts with polar
vander wals - hydrophoic interact when close
Phospholipids spontaneously form
bilayers
Micelle
single layer of lipids
shape of lipid
determines structure
Hydrophobic efects of lipid bilayer
excule hydro from enviorment - relase H2O from hydrpobic regions
large tear in membrane
requires energy to repair - not self seeling
small tear in bilayer creates __
and ___ to elimate (above)
only way to avoid (above) is ___
creates a free edge with water, which is energetically unfavorable
Lipids rearrange spontaneously to eliminate free edge
The only way to avoid free edges is formation of a sealed compartment
Lipid Bilayer is a __
able to __
2D Fluid
diffuse freely within plane of bilayer. Proteins “dissolved” in the lipid bilayer mediate functions of the membrane.
Lipids difuse
laterally
Lipids flip flop with
flippase
enzime that catolizes this
Lipid Flexion
Lipid Rotation
Liposomes are __
synthetic (artifical) lipid bilayers
formation of vesicles
Implcations/Uses of Liposomes
model systems to studdy membrane properties
delevery systems (non carriers) in drug delevery (ex. targeted way to reach cancer cells)
target specificity - specific ligans for specific cells
good carrer - ampipathic (drug of intrest water soluble also good for medications that get stuck in blood/plasma - protective coating - last longer - get to target)
Can liposomes fuse sponstanously?
NO
hydration scheels prevent this - are a barier - regulate process (so dont fues and ex. nutrents get to their targets)
have to get very clse so that fusion proties can catolize the fustion only with target membranes
Soap consists of
salts of fatty acids
When added to water, soap forms a
micelle
traps dirt on/in hydrophobic inside
How does soap inactivate Sars CoV2
Homophobic attract to hydrophobic in virus and membrane protines → loosens the bilayer → extracts protines needed for infection
Types of membrane lipids
Phosphoglycerides (glycerophospholipids)
Sphingolipids
Glycolipids (Glycosphingolipids)
Sterol
Fatty Acids can be___ Or ____
unsaturated - cis double bond - causes kink/bend
Saturated - strait - fully saturated with H
Unsaturated faty acids are more
fluid
Don’t pack as tightly
Trygliserides are
not membrane lipids
are source of energy
are neutral/have no net charge
entirely hydrophobic and therefore less bulky
Phosphoglycerides are the main phospholipid in __
- Main phospholipid in most animal cell membranes
Phosphoglyceride motif
- Glycerol backbone (has three carbons)
- Fatty acid chains esterified to (glycerol C1, C2)
- Phosphate (C3 on glycerol)
- Alcoholic base (phosphoester linkage), known as head group
Head group has ___ linkage
phosphoester linkage
Phosphoglycerides are Formed from ____ Intermediates
Phospholipid
Phosphatidic acid (PA) & Diacylglycerol (DAG)
Phosphatidic acid (PA) lacks ___
is an important ____
Phosphatidic acid (PA) lacks base. Important precursor intermediate during phospholipid (PL) biosynthesis in the ER.
Diacylglycerol (DAG) lacks __
Generated during ___
•Diacylglycerol (DAG) lacks PO4 and base.
–Generated during Phospholipid biosynthesis and by Phospholipase C hydrolysis of polar head groups
Serine family of alcoholic bases.
phosphatidylserine (PS) - Serine - Ameno Acid
phosphatidylethanolamine (PE) - Ethanolamine - via decarboxolation of Ser.
phosphatidylcholine (PC) - Choline - Via methalation of ethanolamte
Inositol-derived Head Groups
PI-phosphate (PIP), PI-bis-phosphate (PIP2).
Inositol ring may be substituted with one, two, or more phosphates.
Precursors to highly-potent signaling molecules IP3.
Are smaller consenuates in bilayer
Inositol is a ___
forms ___
Inositol—a six-carbon cyclic sugar alcoholic ring. Forms phosphatidylinositol (PI).
Variations in head group (Phosphoglycerides)
Membrane surface properties of these molecules
make them important in cell recognition, signaling, and binding.
Fatty acid chains can vary in length and saturation, resulting in a variety of functions
ex. neg charge - areas consentrated with strongly negative - attracts cetrine (ex. enzimes)
Sphingolipids
(Sphingosine based backbone)
Sphingosine is an
amphipathic long-chain amino-alcohol hydrocarbon
Precursor to all sphingosine-based membrane lipids. Formed from serine and palmitic acid (C16 fatty acid)
Ceramide is the __
Formed by __
is intermedate for ___
Simplest Sphingolipid, Pro-apoptotic molecule, and Main component of epidermis layer of skin (maintain barrier, waterproof)
Formed by addition of fatty acid to amine of sphingosine
Intermediate (foundation) for all sphingosine-based lipids.
Sphingomyelin
(Major class of Sphingolipids)
Phosphocholine or phosphoethanolamine as head group
Major component
of myelin-the insulating sheath for axons
typically in extracellular leaflet
Glycolipids
Resemble ___
___ linked to ___ by___ via ___
Found ___
(aka Glycosphingolipids)
Resemble sphingolipids, but instead of phosphate linked head group, they have sugar
Sugar linked to ceramide by O-glycosidic bond via the OH group of ceramide.
Found exclusively in the noncytosolic
monolayer of cell membranes
noncytosolic
fasing extereor
corrospons to areas that they are made in
Exampels of Glycolipids
–Cerebrosides: 1 sugar
–Gangliosides: >1 sugar with 1 or more sialic acids - neg charge. (role in cell interaction, recognition, signal transduction(voltage difference across membrane) - found more abundantly in nervous sytem
Gangliosides
(charged glycolipids)-electrical effects
Function of glycolipids
Gangliosides (charged glycolipids)-electrical effects
Play a role in altering the electrical field across a membrane and the concentration of ions
Tay Sachs Disease
a genetic mutation alters the lysosomal (organelle containing digestive enzymes) enzyme that breaks down gangliosides, which accumulate in nerve cells - particularly in the brain
early in life - devolop normal
as progrss - delay moto function, cognitive function, and not eat, loose ability to see and hear
avg. lifespan - 5 yrs
Sugar Abbreviations
Glc
Gal
GalNAc
Fuc
Glc - Glucose
Gal – Galactose
GalNAc – N-acetyl-Galactosamine
Fuc - Fucose
basis of blood typing
glycolipids
are blood group antigens
Asymmetry of Lipid Bilayer
Two monolayers of lipid bilayer in many membranes very different
Two differnt allow for functionality - differnt extra and intra cellular
extracellular and cytoplasmic suffaces a symetry
–Phosphatidylcholine and sphingomyelin(extracellular surface)
•cellular recognition, interactions, protection, insulation.
–phosphatidylserine (cytoplasmic surface)
•negative charge - interactions with protein kinases (PKC). - due to Phosphatidylserine (relay signal transduction because attract PKC)
Cholesterol is a
sterol
Cholesterol is a
sterol
Cholesterol contains __
is__
in ___
make __
•Contains a rigid ring structure, with attached polar hydroxyl group and short nonpolar hydrocarbon chain
is very hydrophobic
- Only in eukaryotes
- We make it! (synthsize on own)
Cholesterol functions as sterioid precusor of ___
Ciritcal in mediating __
bile salts
sterioud hormones
and vitamin D
medating membrane fluidity
Cholesterol is carried by __
lipoprotein - is a carriing device - allows cholesterol to be packaged outer - phospholipids - polar
LDL
LDLs can transport cholesterol into artery walls, including arteries in the heart, arteries leading to the brain and arteries in the brain itself.
This leads to the formation of “plaques”. Plaques can slow or obstruct the flow of blood.
is a lipoprotein
_ transports cholesterol into the artery walls
This can lead to the formation of __
LDLs
including arteries in the heart, arteries leading to the brain and arteries in the brain itself.
This leads to the formation of “plaques”. Plaques can slow or obstruct the flow of blood.
The temperature at which phase transition occurs is called __
Phase Transition Temperature.
Fluidity and phase temp
High Fluidity = Low Phase Transition Temp.
Low Fluidity = High Phase Transition Temp.
High Fluidity Means That Lipids Resist Gelling.
Low Fluidity Means That Lipids Gel Easily
Factors Affecting Phase Transition Temperature
aka fluidity
Fatty acid chain length (proportonal to)
Fatty acid double bonds (inversly proportional to)
how fatty acid chain length affects fluidity
Reduced chain length enhances lateral diffusion by reducing the tendency of hydrocarbon chains to interact. Gels at lower temp.
Longer chains - dec fluididty -tangled up with other - steric hindrence
how fatty acid double bonds affects fludity
Double bond introduces a kink in acyl chain. - do not pack as tightly
Thus, unsaturated acyl chain containing phospholipids gel at lower temp.
“Tight Seal” in sterols
Due to interactions near the head groups, sterols reduce permeability to small solutes.
Cholesterol and Fluidity
is a mediator of membrane fluidity
At normal body temperatures cholesterol
Interactions of rigid ring structure of cholesterol and phospholipid fatty acid tails reduces mobility of phospholipids, decreases fluidity.
At low temperatures cholesterol
prevents phospholipids from packing tightly with other phospholipids, increases membrane fluidity
changes of fluididy in diff temp with and without cholesterol
Cholesterol is in these cells
eukaryote but NOT procaryote
partly hydrogenated =
partly hydrogenated =
trans fats
trans fats
Partially hydrogenated vegetable oils formed by a chemical hydrogenation process
Double bond straightens the molecule
How would trans fatty acids affect cell membrane?
cis to trans - no kink - behave like saturated - longer shelf life
trans fats affects on HDL and LDL
Increased LDL (Bad cholesterol)
Decreased HDL (Good Cholesterol)
