The fluidity of the cell membrane is directly affected by temperature. The cell membrane is primarily composed of a lipid bilayer, which consists of phospholipids, cholesterol, and proteins. The phospholipids have hydrophilic heads and hydrophobic tails, which arrange themselves in a bilayer to create a semi-permeable barrier for the cell.As temperature increases, the kinetic energy of the molecules in the lipid bilayer also increases, causing them to move more rapidly. This increased movement results in greater fluidity of the cell membrane. The phospholipids become more loosely packed, and the membrane becomes more flexible and permeable. This increased fluidity can facilitate the movement of proteins and other molecules within the membrane and across the membrane.Conversely, as temperature decreases, the kinetic energy of the molecules decreases, causing them to move more slowly. This reduced movement leads to a decrease in the fluidity of the cell membrane. The phospholipids become more tightly packed, and the membrane becomes more rigid and less permeable. In extreme cases, if the temperature drops too low, the membrane can undergo a phase transition from a fluid state to a gel-like state, which can impair the function of membrane proteins and compromise the cell's viability.Cholesterol also plays a role in modulating membrane fluidity. At high temperatures, cholesterol can restrict the movement of phospholipids, reducing fluidity and maintaining membrane integrity. At low temperatures, cholesterol can prevent tight packing of phospholipids, thus preventing the membrane from becoming too rigid.In summary, the fluidity of the cell membrane is directly influenced by temperature, with higher temperatures increasing fluidity and lower temperatures decreasing fluidity. This fluidity is essential for maintaining proper cell function, including the movement and function of proteins and other molecules within and across the membrane.