Membrane fluidity refers to the flexibility and movement of the lipid bilayer in cell membranes. This property is crucial for various cellular functions, including the transport of materials, communication between cells, and the ability to adapt to changes in temperature. The composition of the membrane, including the types of lipids and proteins present, influences its fluidity. Factors such as temperature and the presence of cholesterol also affect membrane fluidity. At higher temperatures, membranes become more fluid, while lower temperatures can make them more rigid. Cholesterol helps maintain optimal fluidity by preventing the fatty acid chains from packing too closely together, ensuring proper membrane function.