18 Lipids and membranes Flashcards
what are the two basic components which make up biological membranes?
it’s made up of lipids and proteins:phospholipids
(glycerophospholipids and sphingomyelin), cholesterol and integral or peripheral proteins
what is the amphipathic nature of phospholipids?
(polar) head groups, and (non-polar) hydrophobic fatty acid tails or alipathic tails
how are carbohydrates present in biological membranes?
found as glycolipids or glycoproteins on the extracellular side of the membrane
the structure of glycolipids
a sphingosine backbone with one to many sugars attached to the lipid
what’s a micelle and how does it function?
an amphipathic compound made up of lipid bilayer that interacts with aqueous systems and forms spheres, with an entire hydrophobic core
Involved in intestinal digestion and absorption of lipids
what’s a liposome and how does it function?
form spherical vesicles separating the external env’t from an internal aqueous compartment
Involved as carriers of non-permeable solutes
types of movement of phospholipids
rapid lateral diffusion (side to side movement), rapid rotational diffusion (spinning in place) and rapid flexing of hydrocarbon chains
secondary structures found in transmembrane segments of integral membrane proteins
alpha-helices and B-barrels
definition of lipid anchors
lipid anchors have covalently linked lipid inserted into the lipid membrane and attached to peripheral protein.
GPI anchor
phosphatidylinositol (in the membrane) attached to covalently linked sugar residues and covalently bound to the carboy terminus of a peripheral protein
Fatty acid linked anchor
fatty acid linked to the amino terminus of a peripheral protein
isoprenoid lipid anchor
isoprenoid lipid attached to a sulfur group and a peripheral protein
factors affecting membrane fluidity
temperature and degree of unsaturation of fatty acid chains
temperature and membrane fluidity
increasing Temperature (heating up the lipids) leads to greater membrane fluidity
degree of unsaturation of FAs and membrane fluidity
the more unsaturated the Fatty acid, the more kinks from double bonds, and poor packing leads to greater membrane fluidity
cholesterol’s effect on membrane fluidity
overall, net lowering in membrane fluidity, cholesterol lowers membrane fluidity due to is structure, rigid plank of four fused rings, limits rotational ability of the fatty acid tails. cholesterol can also increase membrane fluidty in the hydrophobic core of the lipid bilayer since cholesterol does not extend into this region
role of lipid rafts
segregate and concentrate or exclude certain proteins to facilitate their activity
lipid rafts are…
organized bilayer structure with particular lipids and proteins present, and distinct from the surrounding bilayer. lots of cholesterol and tend to have longer fatty acid chains
outer leaflet of lipid rafts contain
glycosphingolipids and cholesterol
inner leaflet of lipid rafts contain
sphingomyelins and cholesterol
forces which drive the formation of lipid bilyers
hydrophobic forces- hydrophobic, fatty acid tails tend to come together and van der Waals forces
