Which of the following statements about a typical plasma membrane is correct?a. Phospholipids are the primary component that determines which solutes can cross the plasma membrane.b. The plasma membrane is a covalently linked network of phospholipids and proteins that controls the movement of solutes into and out of a cell.c. Carbohydrates on the membrane surface are important in determining the overall bilayer structure.d. The two sides of the plasma membrane have different lipid and protein composition.e. The hydrophilic interior of the membrane is composed primarily of the fatty acid tails of the phospholipids.

The fatty acid tails of phospholipids are hydrophobic – meaning they are ‘water-hating’. This is why they are in the middle of the bi-lipid layer of the cell membrane 'hiding' from the 'watery' environment of a cell. This poses a challenge in the diffusion of large and charged molecules across the membrane -such as sodium ions. Such molecules need transmembrane protein channels to help them cross the membrane. These are called integral proteins because they are part and parcel of the cell membrane. The cell membrane, in addition, also has glycolipids and glycoproteins on its surface that are significant in the identification of the cell by other cells.