Flashcards in S+F OF THE PLAMSA MEMBRANE Deck (56):
what are the 4 components of the eukaryotic cell?
why does the interior of the cell need to be physically separated from the surrounding environment?
To keep desirable substances in
To keep undesirable substances out
what is the function of the plasma membrane?
Sites of metabolic activities
what is hypotonic?
what is hypertonic?
what happens if the membrane is ruptured?
escape of cell contents
what is compartmentalisation?
Applies to most internal organelles
Needed for chemical activities
what is Robertson’s “unit membrane"?
Membranes found to have “railroad track” structure
what is the structure of the unit membrane?
Two dark lines separated by a lightly stained central zone: “A trilaminar (three-layered) staining pattern”
what does the Triliaminar staining pattern by TEM show?
2 dark lines: outer & inner layer (containing the polar head groups)
separated by light central space (containing the hydrophobic region of the lipid molecules which do not stain)
what does the Fluid Mosaic Model show?
2 fluid layers of lipid
Proteins within or on lipid layers
how are lipid molecules arranged in the plasma membrane?
what is amphiphilic?
hydrophilic & hydrophobic regions
what is the polar head?
a hydrophilic (water-loving)
what are non polar tail?
a hydrophobic (water-fearing)
give examples of membrane lipids
what are phospholipids?
2 hydrocarbon tails; usually fatty acids
Tails differ in length between 14 -24 C atoms long
Cis-double bonds in one tail creating a small kink
how are lipid molecules arranged in phospholipids?
spontaneously aggregate to keep their hydrophobic tails in the interior and expose their hydrophilic heads to water
what are the 2 ways lipids can be arranged?
what is cone-shaped?
lipid molecules (single chain) form micelles
what is cylinder-shaped?
phospholipid molecules (double tailed) form bilayers
what are phosphoglyceride?
give examples of phosphoglyceride in the PM
what is the main sphingolipid in PM?
what is the structure o the phospholipid?
Polar head (such as choline, ethanolamine, serine, inositol)
Glycerol or sphinogosine based
how are glycolipids formed?
by the addition of CHO group(s) to lipids
what are glycolipids?
what are sphingolipids?
what are Glycosphingolipids?
Combination of glycerol and sphingosine-based
what are the most common glycosphingolipids?
what is the structure of the glycolipid?
Carbohydrate head group
Glycerol or sphinogosine based
what are sterols?
Eukaryotic PM large amounts of cholesterol
what do sterols effect?
increase permeability barrier properties of PM
maintain stability+integrity of PM
what does the fluidity of the plasma membrane depend on?
what is the composition of the PM?
shorter chain length
what is the effect of having a shorter chain length?
reduces the tendency of the tails to interact with one another, in both the same and opposite monolayer
what is the effect of cis-double bonds?
produce kinks in the hydrocarbon chains that make them more difficult to pack together.
what is the effect of temperature on PM fluidity?
The movements decrease when temp drops and increase as it rises
how do phospholipids molecules move within the memb?
Rotation about its long axis
Lateral diffusion by exchanging places with neighbouring molecules in the same monolayer
Transverse diffusion, or “flip-flop” from one monolayer to
the other (rare)
what are the 3 classes of proteins?
where are integral proteins found?
Embedded within bilayer
what do integral proteins contain?
what is the function of hydrophobic segments in integral proteins?
have affinity for hydrophobic interior of bilayer
what is the function of hydrophilic regions in integral proteins?
extend outward from the membrane into the aqueous phase
what are peripheral proteins?
More hydrophilic, lack the hydrophobic segment
where are peripheral proteins found?
Located on surface of PM / linked to polar head of phospholipids – glycosylphosphatidylinositol (GPI) anchors
what are lipid anchored proteins?
Hydrophilic / on surface of memb
Attached to lipid molecules in bilayer
what are Lipid rafts?
Transient clusters/associations of lipids and proteins within membrane
what is the function of Lipid rafts?
Proposed to increase functional efficiency
what is the barrier function of the PM?
Allow nutrients to enter & keep out harmful
Defines boundaries of cell & compartments
Separates organelles into discrete regions
what is the transport function of the PM?
Controls the passage of substances into & out of the cell
Proteins in bilayer act as pore channels/carriers
what can't criss the lipid bilayer?
Large molecules, ions, hydrophillic substances
what are the 2 proteins that allow transport to occur in the PM?
Ion channel proteins
how does signal detection occur in the PM?
Cells receive info from their environment via signals
Chemical signals bind to specific receptor proteins
what happens when the signal binds to receptor?
molecular event inside membrane