1.2 The Nucleus and DNA
All About the Nucleus
Why is the Nucleus so Important?
You won't find the nucleus in just any cell. For example, bacteria are prokaryotic (this means “before the nucleus”). These cells do not have a nucleus, although they do still have DNA. They also have no membrane-bound organelles, such as chloroplasts or mitochondria.
On the other hand, eukaryotic organisms (animals, plants and fungi) do have nuclei in their cells.
Structure
Notice in this diagram that a membrane surrounds the nucleus, and that there are holes or pores, in this membrane. The membrane around the nucleus is similar to the cell membrane because both allow only certain substances to pass through.
Function
The nucleus is often called the 'control center' for a cell, but what does this really mean?