What is the cell membrane made up of?

The cell membrane is primarily composed of **phospholipids**, along with **proteins**, **cholesterol**, and **carbohydrates**. The phospholipid bilayer forms the fundamental structure, while proteins are embedded or associated with the membrane, cholesterol helps to maintain fluidity, and carbohydrates play roles in cell recognition and signaling. So the correct answer from your options is:

**Mostly phospholipids with proteins, cholesterol, carbohydrates.**