What happens to membrane fluidity at lower temperatures?

At lower temperatures, membrane fluidity decreases due to the closer arrangement of lipid molecules. In a biological membrane, lipids can move laterally within the bilayer, contributing to its fluid nature. However, when temperatures drop, the kinetic energy of these lipids decreases, causing them to become less mobile. This results in a more rigid structure.

In particular, the fatty acid tails of phospholipids tend to pack more closely together when temperatures decline, which restricts their movement. As a result, the overall fluidity of the membrane diminishes, making it less capable of expanding and contracting in response to environmental changes. This decrease in fluidity can affect many membrane functions, such as the transport of molecules and the functionality of membrane-bound proteins.

Understanding this relationship between temperature and membrane fluidity is vital for the concept of homeostasis in cells, as organisms often need to maintain appropriate membrane characteristics under varying environmental temperatures.