How is the cell membrane affected by temperature?

Cells and cell membranes function best at normal physiological temperatures. Both higher and lower temperatures affect various aspects of the cell membrane including its structure and permeability. They also affect how well molecules found within the membrane can function. Higher temperatures increase fluidity and permeability. Lower temperatures lower fluidity and permeability. Too high or too low temperatures can cause serious damage to the cell and the cell membrane. Prolonged exposure to extreme temperature ranges can kill the cell. 

• At temperatures slightly higher than the physiological temperature, the fatty acid tails of the phospholipids become less rigid and the phospholipids have enough kinetic energy to overcome the intermolecular forces that hold the membrane together. This increases membrane fluidity as well as its permeability. When the temperature is much higher than the physiological normal, it damages the integral and peripheral proteins in the membrane. At dangerously high temperatures the proteins may denature or break down completely, increasing the fluidity of the cell membrane to dangerous levels and allowing potentially dangerous molecules to pass through the membrane. 
• At lower temperatures, the phospholipids in the bilayer have lower kinetic energy. Their fatty acid tails move less, are more rigid, and cluster together more closely. This strengthens intermolecular interactions and decreases membrane fluidity and permeability, potentially preventing essential molecules such as oxygen and glucose from passing through the membrane into the cell. Low temperatures also slow down cell growth. Sub-freezing temperatures or prolonged exposure to temperatures much below the physiological normal can cause the liquid in the cells to freeze and form into sharp crystals that are capable of piercing the cell membrane and potentially killing the cell.