With responsibility for so many critically important functions it’s no surprise that the nucleus is the largest organelle in the cell. Everything that a cell needs to do in order to survive and reproduce (divide) is the responsibility of the nucleus. Looking like a large black spot that’s been plonked into the cell cytoplasm, it can be found anywhere in the cell, not necessarily the centre, which is where most people imagine it to be. Although, it is generally not situated near the membranes.
The Contents of the Nucleus
The nucleus is a full house, locked and loaded with chromosomes, DNA, proteins and much more. The structures are important for the vital functions of the cell nucleus. Some of the key structures of the cell nucleus are;
Chromatin – is the name given to the substance that contains, DNA, RNA and proteins and makes up chromosomes.
Nuclear Envelope – this is a double membrane structure that encloses the nucleus. The membranes are connected at sites known as nuclear pores. At these locations substances such as RNA and transcription factors can pass through. The envelope is a physical barrier separating the contents of the nucleus from the surrounding cytoplasm.
Nucleosomes – is the name given to a subunit of short lengths of DNA that are coiled around a core unit of histone proteins.
Histones – these are proteins inside chromosomes. They act as spindles that DNA can wind around. They also have a role in gene expression.
Chromosomes and DNA – the nucleus is home to most of the cell’s genetic material. It’s in the form of DNA which is organised into chromosomes. In human cells there are 46 chromosomes in each cell, apart from the sperm and egg cells which have 23 chromosomes.
Nucleolus – commonly referred to as a sub-organelle of the nucleus, and it’s where the protein factories called ribosomes are made.