The outer boundary of a cell is the cell membrane.
The cell membrane, also known as the plasma membrane, is a crucial structure that separates the interior of the cell from the external environment. It is primarily composed of a phospholipid bilayer embedded with proteins, carbohydrates, and cholesterol.
The main functions of the cell membrane are to protect the cell, provide structural support, and regulate the passage of substances in and out of the cell. This selective permeability is essential for maintaining homeostasis, allowing essential nutrients to enter while keeping harmful substances out.
In summary, the cell membrane plays a vital role in communication and interaction with the surrounding environment, making it a fundamental component of all living cells.