Integral membrane proteins are proteins that are permanently attached to the cell membrane. They span the lipid bilayer, meaning they have regions that extend both inside and outside the cell. These proteins play crucial roles in various cellular functions, including transport, signaling, and maintaining the structure of the membrane. These proteins can be classified into two main types: transmembrane proteins, which pass through the membrane, and lipid-anchored proteins, which are attached to the membrane by lipid tails. Integral membrane proteins are essential for processes like cell communication and nutrient transport, making them vital for cell survival and function.