House mice are small mammals that do not hibernate in the wi

House mice are small mammals that do not hibernate in the winter, instead maintaining a normal body temperature all winter, while chipmunks are small mammals that do hibernate in the winter, dropping thier body temperature to 4 degree celsius during hibernation. When the lipid composition of the cell membranes house mice and chimpunks are examined in the middle of winteR, it is found that one of the mammals has much more of the fatty acid oleic acid (C18:1) compared to Steric acid (C18:0) in its cell membranes. Which mammal would you expect to more oleic acid vrs steric acid? Why?

Solution

Here Oleic acid (18:1) represents unsaturated fatty acid and stearic acid (18:0) is saturated fatty acid. Now between house mice that do not hibernate and chipmunks that do hibernate,we expect to have chipmunks to contain much more of Oleic acid (unsaturated fatty acid) than stearic acid (saturated fatty acids) for two main reasons-

1. More amount of unsaturated fatty acid(Oleic acid) in the membrane decreases the melting point of the membrane so that membrane remains fluid even at very low temperatures of 4^o C during hibernation.Because of this membranes do not completely freeze and fluidity of membrane phospholipid is crucial for proper functioning of membrane associated enzymes, diffussion within membranes and maintenance of transmembrane gradient and regaining membrane activity is easy and fast without spending any energy.

2.The fat depots play an important resource of energy during hibernation and when the fat depots are fluid in nature due to more amount of unsaturated fatty acid deposition, mobilization of this resource is easy and cost effective no extra energy in form of heat is utilized to mobilize fats as they are already in the fluid state.

So based on these points we expect to have chipmunks containing more unsaturated fatty acid (Oliec acid) as their body temperature drops to freezing conditions during hibernation that leads to freezing of the membrane but this freezing is avoided by incorporating more of unsaturated fatty acids in the membrane as well as in the fat depots.