Which cellular structure is known as the control center of the cell?

The nucleus is known as the control center of the cell because it houses the cell's genetic material, DNA, which contains the instructions necessary for the development, functioning, and reproduction of the organism. It is responsible for regulating many cellular activities, including growth, metabolism, and reproduction, by controlling gene expression. The nucleus also plays a critical role in the cell cycle and in processes such as transcription and replication of DNA.

In contrast, the cytoplasm is the jelly-like substance that fills the cell and contains various organelles, but it does not serve as the control center. The cell membrane acts as a protective barrier that regulates what enters and exits the cell but does not have a role in controlling cellular activities. Ribosomes are essential for protein synthesis but do not govern the overall functions of the cell; they operate under the instructions provided by the nucleus. Thus, the nucleus is clearly established as the central hub for cellular control and regulation.