Cells are the basic units of life. All living things are made up of one or more cells. Cells perform all the functions necessary for life, such as taking in nutrients, producing energy, eliminating waste, and replicating themselves.
The cell is the smallest unit of an organism that can carry out all the processes necessary for life. There are many different types of cells, each with a specific function. For example, nerve cells transmit signals from the brain to other parts of the body; muscle cells contract to move the body; and blood cells transport oxygen and nutrients throughout the body.
All cells have a membrane that separates them from their environment and controls what enters and leaves the cell. The interior of the cell is divided into two main parts: the nucleus and cytoplasm. The nucleus contains DNA, which holds the instructions for making proteins, which are essential for all cellular activity. The cytoplasm contains organelles that carry out specific functions within the cell.
Cells reproduce by dividing into two new cells identical to themselves. This process is called mitosis. In order for a cell to divide, it must first replicate its DNA so that each new cell has a complete set of instructions. Once replication is complete, the cell divides into two equal halves, each with its own complete set of DNA. Mitosis ensures that each new cell has exactly the same genetic information as its parent cell so that no important information is lost during reproduction.