O cell nucleus is the cell region eukaryote in which the control of cellular activities takes place. This is where we find the chromosomes, structures that consist of DNA and associated protein molecules. In the nucleus, all types of RNA are also synthesized, which are later transferred to the cytoplasm.
→ core structure
The nucleus, which measures about 5 µm in diameter, is made up of the nuclear envelope, chromatin, nucleolus, nuclear matrix and nucleoplasm.
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Nuclear envelope: The nuclear envelope, also called the caryotheca, is formed by two membranes and guarantees the separation between the content of the nucleus and the content of the cytoplasm. The outermost membrane is continuous with the granular endoplasmic reticulum, with adhered ribosomes. Between one membrane and another, we find a space: the perinuclear cistern.
The nuclear envelope has pores and a structure called the pore complex, which works by selecting molecules that enter and leave the nucleus. In pores, the inner and outer membranes are continuous.
Chromatin: Chromatin is composed of filaments of DNA associated with proteins, mainly the histone protein. It's the chromatin that makes up chromosomes. Two types of chromatin can be identified in the nucleus: a heterochromatin and the euchromatin. In the latter, the DNA is uncondensed, making it possible to transcribe the genes. In heterochromatin, the DNA is tightly packed.
Nucleoli: The nucleoli are regions specialized in the production of ribosomes. In this location, mainly ribosomal RNA and proteins are found. Ribosomal RNA is synthesized from DNA.
Nuclear matrix: The nuclear matrix works as a skeleton that supports the chromosomes, which have a fibrillar structure.
Nucleoplasm: Component that fills the space between structures present in the nucleus, such as the nucleolus and chromatin.
Heads up: althoughand the nucleus contains the cell's DNA, he it is not the only place where genetic material is observed. It is also possible to verify the presence of DNA in mitochondria and chloroplasts.
By Ma. Vanessa dos Santos Sardinha
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/biologia/o-que-e-nucleo.htm