We explain what the nuclear membrane is and how it is composed. Also, what are its general characteristics and functions?
What is the nuclear membrane?
The nuclear membrane or nuclear envelope belongs to the endomembrane system of the cell. It is a complex structure with a porous appearance that covers the core.
The nuclear membrane is composed of two concentric layers that have pores. These layers fuse and form nuclear pores that are perforations in the membrane.
The main function of the nuclear pores is to allow communication of the cell cytoplasm with the interior of the nucleus. Between both membranes or concentric layers, there is a distance between 20 and 40 nanometers. There is the perinuclear cistern.
The main function of the nuclear membrane is that chromosomes can be attached to the interior of the nucleus.
Nuclear membrane characteristics :
Structure of the nuclear membrane
These membranes are not continuous but have interruptions called pores
. These pores allow the exchange of material between the cytoplasm and the nucleoplasm. The nuclear membrane is composed of 2 lipid bilayers that will be described below:
- Outer membrane. This is the membrane that connects to the cytoplasm. The outer part of this membrane is called the nuclear outer lamina. This sheet is made up of proteins. It can be presented as a continuous layer, other times it has the appearance of a honeycomb.
- Inner membrane. Separate the nucleoplasm with the nuclear space. Has contact with nuclear material.
Ribosomes are complexes of proteins that are present in the outer membrane
. They serve to synthesize proteins from genetic information.
It is present in the inner layer of the nuclear membrane. DNA and proteins are attached there
. There are 2 types of chromatins:
Cistern or perinuclear space
It is the layer that is between the other 2 membranes
. It forms a unit with the rough endoplasmic reticulum.
Nuclear pore complex
They are communication gates between the nucleus and the cytoplasm
. They cross the nuclear membrane and reach the cytoplasm. Each pore is made up of more than 50 proteins. It is the set of these proteins that makes up the pore complex.
The nucleoplasm has direct contact with the inner layer of the nuclear membrane through the nuclear lamina. Within this nucleoplasm are the chromatin fiber and the nucleolus
It has direct contact with the outer membrane of this nuclear envelope.
This sheet is made up of intermediate filaments
. It has the function of support for the nuclear envelope. It does not have continuity in the pores but is interrupted. This lamina, in certain cells and during the prophase of mitosis, disintegrates and is reconstituted in the therophase.
During cell division, the cell envelope can remain or disappear depending on the living being to which the nuclear membrane belongs. In closed mitosis, the nuclear membrane is maintained while in open mitosis it disappears and re-forms when the division of genetic material is complete.
What is the function of the nuclear membrane?
The nuclear membrane has several main functions:
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- Transcribe DNA into RNA.
- It translates RNA into proteins.
- They prevent the exit of DNA and the entry of cytoplasmic enzymes.