The organelle that manages cell functions in a eukaryotic cell is the nucleus. Most eukaryotic cells have a single nucleus; however, some organisms may have several nuclei per cell.
The cell nucleus is generally spherical in shape. The nuclear envelope protects the nucleus and allows only certain substances to pass between it and the cytoplasm. Within the nucleus exists the nucleolus, a spherical structure that plays some role in the aging of cells.
This central organelle's function is analogous to that of the brain; it takes in information from the rest of the cell and coordinates the different cellular activities, from cell growth to the making of proteins. The nucleus also contains the hereditary material, the DNA, of the cell.