Virginia 7th Grade Science SOL Practice Test

The nucleus serves as the cell’s control center because it houses the DNA, which contains the instructions for building proteins and directing cellular activities. By controlling which genes are turned on or off, the nucleus determines what proteins are made and when, guiding the cell’s functions and responses. In short, it sets the plan and oversees how the cell carries it out. Other organelles do important jobs too—mitochondria provide energy, the Golgi apparatus packages and ships proteins, and the endoplasmic reticulum helps build and transport molecules—but the nucleus is the main command hub that directs everything.