The correct answer is D. It is the protective barrier that encloses the cell.
The cell membrane is a thin, flexible layer that surrounds the cell, separating the inside of the cell from the outside environment. It is made up of a phospholipid bilayer and contains various proteins and other molecules that help the cell maintain its structure and function. The cell membrane is essential for the survival of the cell and plays several important roles:
It acts as a barrier: The cell membrane separates the inside of the cell from the outside environment, creating a controlled environment inside the cell that allows it to carry out its functions without interference.
It regulates the movement of materials: The cell membrane is selectively permeable, meaning that it allows some molecules to pass through while preventing others from entering or leaving the cell. This regulation is important for maintaining the balance of materials inside and outside the cell.
It provides structural support: The cell membrane helps to maintain the shape of the cell and provides support for the internal structures of the cell.
Overall, the cell membrane is essential for the survival and proper functioning of all cells.