Where is nuclear envelope located in a cell

The inner membrane is constituted by a network of filaments called nuclear lamina. The lamina attach to chromosomes. It also acts like a shield for the nucleus. The outer and the inner membranes are connected by the nuclear pores. In mammals, the nuclear envelope spectrin repeat proteins are expressed in the outer membrane.

These proteins connect the cytoskeleton s in the cytoplasm to the nucleoskeleton in the nucleoplasm. This connection aids in the positioning of the nucleus within the cell.

During cell division, the nuclear envelope undergoes major changes in animal and plant cells. The nuclear envelope disintegrates to allow the spindle fibers to access the chromosomes in the nucleus.

An exception to this is the yeast cells whereby the nuclear envelope stays intact during cell division. In animal and plant cells, the nuclear envelope breaks down into pieces during prometaphase of mitosis. Then, during telophase, the nuclear membrane reforms. The reformation process remains unclear how it proceeds. It is postulated to occur via vesicle fusion or probably by reshaping of the endoplasmic reticulum, enclosing the nuclear region with a new nuclear envelope.

The presence of the nuclear envelope prevents the easy passage of large molecules e. Although the nuclear envelope is perforated with nuclear pores, large molecules would still need a nuclear transport mechanism in order to enter and exit the nucleus. Small molecules, such as ions, can pass through the nucleus with ease.

However, cargo proteins and RNAs that need to be transported require importins and exportins to enter and exit the nucleus, respectively. On one hand, the cargo binds with the importin in the cytoplasm, and then moved into the nucleus through the nuclear pore.

In eukaryotic cells, the nucleus is separated from the cytoplasm and surrounded by a nuclear envelope. This envelope safeguards the DNA contained in the nucleus. In spite of this barrier, there is still communication between the nucleus and the cytoplasm. This communication is regulated by the nuclear pores.

Each nuclear pore is a large complex of proteins that allows small molecules and ions to freely pass, or diffuse, into or out of the nucleus. DNA Gallery.

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