The biologist is most likely studying plasma or cell membranes. As within these membranes, there are both a combination of lipids and proteins arranged in a fluid mosaic manner, in which the 2 main layers arranged are phospholipids.
The structure that is made up of two layers of phospholipids is called the cell membrane.This enables the cell to selectively permeate molecules that go through in and out of the cell. The molecule has two sides: hydrophobic and hydrophilic sides
