What is the function of the lipid bilayer of the plasma membrane?
Lipid bi layer prevents the molecules or ions entering a cell
Well, u said a 'lipid' . These are phospholipid molecules which have a hydrophilic ( water loving) head and a hydrophobic tail (water repelling tail ).
Phospholipid bilayer mainly acts as barrier to the ions and molecules including water from entering the cell. But these ions and molecules can enter the cell by the channel or carrier proteins.
Phospholipid contains cholesterol molecules which can adjust the fluidity of the cell membrane.