Final answer:
The cell membrane is selectively permeable and composed of a lipid bilayer made up of phospholipids. Proteins are involved in transport and communication across the membrane. The cell membrane is not a single layer of molecules.
Step-by-step explanation:
The cell membrane is composed of a lipid bilayer, primarily made up of phospholipids. This structure causes the membrane to be selectively permeable, allowing only certain substances to pass through.
Proteins play a vital role in transport and communication across the membrane. The cell membrane is not composed of a single layer of molecules; it is made up of a double layer of phospholipids.