STRUCTURE AND FUNCTION OF CELLS
In biology, the smallest unit that can live on its own is the cell, which makes up all living organisms and the tissues of the body. A cell has three main parts: the cell membrane, the nucleus, and the cytoplasm. The cell membrane surrounds the cell and controls the substances that go into and out of the cell.
The structure of an object refers to what it is made of and how its parts are put together. For example, the structure of a car depends on how materials such as plastic, metal, and rubber are arranged. The structure of a living thing is determined by the amazing variety of ways its cells are put together.
A single cell has the same needs as an entire organism. For a cell to stay alive, it must perform biological functions. Those functions include obtaining energy, brining nutrients and water, and getting rid of waste. There are many different cells that work together to keep it alive.