Without a nucleus, multicellular life forms, called eukaryotes, would not exist. According to the Molecular Expressions website from Florida State University, the nucleus acts as the administrative center and information processor for the cell by storing its genetic material and coordinating its activities.
Molecular Expressions explains that simple, one-celled organisms, or prokaryotes, such as bacteria, do not have a nucleus. Instead, their genetic material is dispersed throughout the cell. Eukaryotes, on the other hand, require a greater degree of cellular organization because they perform more complicated functions. These functions include cell reproduction, growth, protein synthesis and intermediary metabolism. A membrane separates the nucleus' contents, which include strings of genetic material called DNA, from the rest of the cell. Each nucleus within a human cell contains nearly 6 feet of DNA arranged into a compact structure known as chromatin. This chromatin organizes to form chromosomes during cell division.
Each nucleus also contains at least one nucleoli, an organelle responsible for synthesizing ribosomes, which produce proteins along with other small cell components. The membrane of the nucleus is full of small holes that allow necessary molecules to pass between the nucleus and the rest of the cell, such as building blocks for DNA and RNA and energy-supplying components, notes Molecular Expressions.