Final answer:
Lignin is not present in the cell membrane; instead, it is a component of plant cell walls. The cell membrane contains phospholipids, cholesterol, and glycolipids.
Step-by-step explanation:
The element not present in the cell membrane is lignin. The cell membrane is comprised of phospholipids, which form the bilayer; cholesterol, which provides flexibility to the membrane; and various other components such as glycolipids and proteins. Glycolipids, carbohydrates attached to lipids, are found on the cell surface playing a role in recognition and communication. However, lignin is a complex polymer found in the cell walls of plants, not in the cell membrane. Lignin is not present in the cell membrane; instead, it is a component of plant cell walls. The cell membrane contains phospholipids, cholesterol, and glycolipids.