All eukaryotic cells have a surrounding plasma membrane, which is also known as the cell membrane. The plasma membrane is made up by a phospholipid bilayer with embedded proteins that separates the internal contents of the cell from its surrounding environment.

Composition of the Plasma Membrane in Animal Cells
The plasma membrane of animal cells is composed of a combination of lipids, proteins, and carbohydrates, which work together to maintain the structure and function of the membrane.

Lipids
- The main component of the plasma membrane is phospholipids, which form a lipid bilayer. This lipid bilayer provides the structural framework of the membrane and regulates the passage of molecules in and out of the cell.
- Cholesterol molecules are also present in the plasma membrane, helping to maintain its fluidity and stability.

Proteins
- Integral proteins are embedded within the lipid bilayer and help transport molecules across the membrane, as well as play a role in cell signaling and recognition.
- Peripheral proteins are found on the inner or outer surface of the membrane and are involved in various cellular processes, such as cell signaling and maintaining cell shape.

Carbohydrates
- Carbohydrates are often found attached to proteins or lipids on the outer surface of the plasma membrane. These glycoproteins and glycolipids play a crucial role in cell-cell recognition and communication.
- They also act as receptors for signaling molecules and help the immune system identify foreign cells.
In conclusion, the plasma membrane of animal cells is a dynamic structure composed of lipids, proteins, and carbohydrates, all working together to maintain the integrity and functionality of the cell.