In cell membrane, following are true except:
B i.e. Lipids are symmetricalPropeies of Cell MembraneMembranes are asymmetricalQ sheet like enclosed structure with distinct out and inner surfaces. This asymmetry is attributed to irregular distribution of protein with in the cell membranes external location of carbohydrate attached to membrane protein. (inside - outside asymmetry) specific enzymes are located exclusively on the outside or inside of membranes, (inside - outside asymmetry) gap junction synapses and tight junctions occupy only smaller regions of membrane and generate local (regional) asymmetry there is inside - outside (transverse) asymmetry of the phospholipidsThe choline- containing phospholipids (phosphotidylcholine or lecithin & sphingomyelin) are located mainly in the outer molecular layer; the aminophospholipids (phosphotidyl serine & phosphotidylethanolamine) are preferentially located in inner leaflet. There must be limited transverse mobility (flip- flop) of the membrane phospholipid to maintain this transverse asymmetry. Phospholipids exhibit an extraordinarily slow rate of flip flop. When ceain membrane proteins such as erythrocyte protein glycoplwrin are inseed aificially into synthetic bilayers, the frequency of phospholipid fillip -flop increases as much as 100 folds.Membranes are composed of - lipids, proteins and carbohydrates and membranes are dyanic structure- Major lipids in mammalian membranes are phospholipids (phosphoglycerides > sphingomyelin), glycolipids & cholesterol.Membrane lipids are amphipathetic i.e. contain both hydrophobic & hydrophilic regionsQ.- Membrane lipids are bilayer- Proteins are associated with lipid bilayer (+- covalent linkage) and may be integral or peripheral in location. Ion channels are transmembrane proteins that allow selective entry of various ions; ionophores are molecules that act as membrane shuttle for various ions and aquaporins are proteins that form water channels in ceain molecules.Oleic acid is most abundant unsaturated fatty acid in animal membrane lipids. Sphingolipids are found in membranes specifically in tissues of nervous system. Degree of unsaturation determines fluidity of membrane and cholesterol helps to regulate it.
Lipids are regularly arranged
Lipids are symmetrical
Protein displaced laterally
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