an organelle
The nucleus is an example of an organelle . An organelle is any structure inside a cell that is enclosed by a membrane. Eukaryotic cells may contain many different organelles. Each does a special job. For example, the mitochondrion is an organelle that provides energy to the cell. You can see a mitochondrion and several other organelles in the animal cell in Figure above . Organelles allow eukaryotic cells to carry out more functions than prokaryotic cells can.