The Nucleus is
surrounded by a double membrane and found in all eukaryotic cells.
The nucleus contains the cell's DNA. Mitochondria -
A cell can have hundreds or thousands of mitochondria.
Mitochondria are sometimes described as "cellular power plants," because
their primary function is to convert organic materials into energy
in the form of ATP via the process of oxidative phosphorylation.
Because of this, they are sometimes seen as the cellular equivelant
of the stomach. Endomembrane system - An extensive membrane network
of tubes and cisternae (sac-like structures) comprised of the ER
and Golgi apparatus.
The Endomembrane system manufactures and transports membrane, organellar,
and excreted proteins destined for membranes and secretion.