Absolutely essential for all life on Earth, lipid bilayers are a critical component of all biological membranes, including cell membranes. They are composed of two layers of phospholipids—a class of fat-soluble molecules—positioned such that their hydrophilic, or water-absorbing, heads face outward, and their hydrophobic, or water-repelling, tails face inward, blocking entry of water and water-soluble material into the cell. Why is it important that lipid bilayers are asymmetrical? Discuss
Source: The Free Dictionary