Question

please help me understand this scenario. you have an animal at 20 degrees Celsius and you move it to a negative 20 degrees Celsius and it survives what did it have to do to its cell membrane lipids in order to survive? it made 3 changes. I dont know the changes please help.

or if you have a cell at 20 degrees Celsius and you move it to a very high temperature instead of low what changes in their lipids did they do to survive.

Answer 1

• Cell membrane or plasma membrane is composed of lipid bilayer, with hydrophobic tails within and hydrophilic heads facing outside.
• At lower temperature, the lipid of the cell membrane becomes rigid (membrane fluidity decreases), there is also altered permeability causing the entry of harmful substances. Constant exposure to lower temperatures may freeze the cell components.
• The plasma membrane is composed of 50 % of lipids, which are majorly phospholipids and lesser amount of cholesterol.
• Cholesterol in the plasma membranes help the membrane to maintain fluidity, even when there is drop in temperature.
• More saturated fatty acids in phospholipids increases the rigidity of the membrane, while more unsaturated fatty acids increase fluidity of membrane.
• The temperature between the normal and freezing is termed as transition temperature.
• In organisms that do not have higher cholesterol level, the transition temperature is the function of the type of fatty acid in the membrane.
• Unsaturated fatty acids (UFA) have lower transition temperature than saturated fatty acids (SFA).
• The membrane control system of fatty acyl synthase allows the level of variation of UFA or SFA and retains membrane fluidity at lower temperatures by this transition. Like increase in cis-vaccenic acid and decrease in palmitic acid at lower temperatures.
• Another way certain bacteria cope with decrease in temperature is by increasing the proportion of low-melting point fatty acids (like phospholipids with anteiso-branched-chain fatty acids) in the membrane.