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Library: the nuclear envelope of the eukaryote cell
What is (definition)
The library is also known as a nuclear envelope or nuclear envelope. It is that membrane that serves as a boundary between the cell cytoplasm and the cell nucleus. We found the library only in eukaryotic cells.
The fact that the library exists only in eukaryotic cells makes these cells different from prokaryotic cells. In the latter, the genetic material, involved by nothing, is in direct contact with the cellular cytoplasm.
Summary of Key Features
The library has the following characteristics:
- It is composed of two layers of proteins combined with phospholipid molecules: one layer is facing the cytoplasm and the other is in contact with the interior of the nucleus.
- This membrane model, which is the same as the cytoplasmic membrane, contains a smaller amount of cholesterol.
- Some of the library proteins form pores that allow molecules to transit between the nucleus and the cytoplasm.
There are also important protein groups that facilitate the movement of ribonucleic acids between the nucleus and the cytoplasm.
The outer layer of the library extends into the cytoplasm and is adhered to the membrane of the endoplasmic reticulum, one of the cell organelles.
The importance of the library
The library involves the nuclear content, which most of the time is in the form of chromatin. This chromatin undergoes a folding, composing the chromosomes. During cell division, the library breaks down, releasing the chromosomes. After that, each half of the total number of chromosomes in the nucleus goes to opposite poles of the cell.
The importance of the library goes beyond participation in cell division. It acts as a sort of filter between the cytoplasmic and nuclear environment. In addition, some filamentous proteins present in the library play an important role in some processes. For example, chromatin organization and protection against cell aging.
Some researchers suspect that the cell nucleus arose through symbiosis between unicellular organisms. Some less complex organisms would have been engulfed by a larger organism. Then the simple organism that would have given rise to the nucleus would have lost much of its original characteristics but retained its membrane.