which part of the plasma membrane is nonpolar?

The nonpolar part of the plasma membrane is the interior region formed by the fatty acid tails of the phospholipids. These fatty acid tails are hydrophobic (water-fearing) and nonpolar, which means they do not interact with water or polar molecules. This interior region lies between the two layers of the phospholipid bilayer, while the polar, hydrophilic (water-loving) heads face the aqueous environments inside and outside the cell. Thus, the plasma membrane is composed of a phospholipid bilayer with polar heads on the outside and inside surfaces and a nonpolar, hydrophobic core formed by the fatty acid tails in the middle. This nonpolar core acts as a barrier to polar molecules, allowing the membrane to be selectively permeable.