Membrane fluidity is increased by :
Ans. is 'd' i.e. Linoleic acid One remarkable feature of all biological membrane is their flexibility (fluidity) i.e. their ability to change shape without losing their integrity.The basis for this property is the noncovalent interactions among lipids in the bilayer.The noncovalent interactions provide the lipids with some degree of motion.The fluidity of the lipid membrane depends onTemperatureType of lipid presentAffect of temperature on the fluidity of lipidsAt low temperatureThe lipids are in Gel phase (lipid bilayer is para crystalline)This limits the motion of the lipid molecules and thus their fluidity is decreased.At relatively high temperaturesThe lipids are in a liquid disordered state or fluid state The motion of the lipid molecule is increased The membrane becomes more fluid The temperature at which the structure undergoes the transition from ordered to disordered state is called transition temperature.At intermediate temperatureLipid exists in the liquid-ordered state.There is less than normal motionAt a physiological temperature, the fluidity of the membrane depends upon the type of lipid presentFatty acidThe fluidity of the membrane increases with unsaturated fatty acid e.g. Linoleic acid. The fluidity of the membrane decreases with saturated fatty acid e.g. Stearic acid, palmitic acid.CholesterolAt physiological temperature, the presence of cholesterol decreases the fluidity of the membraneLehninger states "The rigid planar structure of the steroid nucleus, inserted between fatty acyl side chains, reduces the freedom of neighboring fatty acyl chains to move by rotation about their carbon-carbon bonds, forcing acyl chains into their fully extended conformation. The presence of sterols, therefore, reduces the fluidity in the core of the bilayer."Also, knowThe transition temperature will be increased by (i.e. membrane fluidity will be decreased by)presence of cholesterols presence of saturated fatty acid.
Stearic acid
Palmitic acid
Cholesterol
Linoleic acid