Question

On a hot spring day, you collect some skin cells from a black bear that you captured in southern Florida. Meanwhile, a friend of yours who is doing research in northern Alaska also collects skin cells from a polar bear that just woke up from hibernation. You and your friend decide to compare the cell membranes of the skin cells that you collected. With the help of a little cartoon/drawing, explain how you would expect the 2 cell membranes to differ. Make sure that you focus your attention mainly on phospholipids.

Answer 1

• Cell membrane or plasma membrane is composed of lipid bilayer, with hydrophobic tails within the membrane and hydrophilic heads facing outside.
• The plasma membrane is composed of 50 % of lipids, which are majorly phospholipids and lesser amount of cholesterol. The tail may be saturated or unsaturated.
• The saturated and unsaturated fatty acids present in plasma membrane may vary according to the environmental factor such as temperature.
• Black bear resides in region with higher temperature. Thus, the membrane should be able to withstand heat.
• The fatty acids will be more saturated with long and straighter tail. This stabilizes the membrane at higher temperature by increasing the melting or boiling points of the membrane.
• Whereas, in colder region, the lipid may solidify easily. Thus, the lipids are unsaturated with shorter and curved tails.
• This prevents the freezing of the membrane at lower temperatures.