What is the primary function of the plasma membrane in a cell?

The primary function of the plasma membrane in a cell is to protect the cell and regulate what enters and exits it. The plasma membrane serves as a selective barrier that controls the movement of substances, allowing essential nutrients and molecules to enter the cell while preventing harmful substances from crossing in. This selective permeability is crucial for maintaining homeostasis within the cell, ensuring that the internal environment remains stable despite changes in the external environment.

The plasma membrane is composed of a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates that contribute to its function. The proteins serve various roles, including acting as channels for transport, receptors for signaling, and anchors for the cytoskeleton, all of which are essential for the cell’s communication and interaction with its environment.

While genetic storage, protein synthesis, and cellular respiration are vital processes within the cell, they do not describe the primary role of the plasma membrane. Genetic storage is primarily associated with the nucleus, protein synthesis occurs at ribosomes, and cellular respiration mainly takes place in the mitochondria. Thus, the focus of the plasma membrane's function is on protection and regulation, marking it as the correct answer for this question.