The nucleus of a cell is a membrane-bound organelle situated within the cytoplasm and can be thought of as the “brain” of a cell. Without a nucleus a cell would not be able to function since it controls all cell operations.
The nucleus holds the cell’s genetic material in the form of chromatin, which is comprised of DNA, RNA and proteins. When the chromatin fibers are in a condensed form, the nucleus’s chromosomes can be seen. Chromosomes provide the cell's hereditary information, its nuclear genome. Thus, the nucleus regulates gene expression. In comparison to prokaryotes which contain singular, circular chromosomes, eukaryotes contain multiple, singular chromosomes.
In addition to controlling gene expression, the nucleus is needed to mediate replication, it is the site of transcription and it manages processes both inside and outside of this membrane-bound organelle. Figure 1 below provides an image of a nucleus.
Figure 1. The figure above provides a schematic image of a nucleus.
Parts of the Nucleus:
Nuclear Envelope: This is composed of both an outer and inner membrane.
Chromatin: Contains the genetic material.
Euchromatin: Is the less compact form of chromatin.
Heterochromatin: Is the more compact form of chromatin.
Nuclear Pores: These pores are composed of proteins and are found within the nuclear envelope, acting as an aqueous channel.
Title Image Credit: Wikimedia Commons