1. Cell Membrane:

* Function: Acts as a barrier between the cell's internal environment and the outside world. It controls what enters and exits the cell, selectively allowing nutrients in and waste products out. It also plays a role in cell signaling and communication.

2. Nucleus:

* Function: The "control center" of the cell. It contains the cell's genetic material (DNA) in the form of chromosomes. The DNA provides instructions for building and maintaining the cell, and directs all cellular activities.

3. Cytoplasm:

* Function: The jelly-like substance that fills the cell and surrounds the organelles. It provides a medium for chemical reactions to occur, and allows for the movement of organelles within the cell. It also contains various enzymes and other molecules that are essential for cell function.

It's important to note that these are just three of many important parts of a cell. There are many other organelles and structures within a cell that contribute to its overall function.