18 Lipids and membranes Flashcards Preview

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Flashcards in 18 Lipids and membranes Deck (21):

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