[Biology Class Notes] on Eukaryotic Nucleus Pdf

The word nucleus is derived from the Latin word, which means “kernel of a nut”. A nucleus is a large double membrane-bound organelle that contains the cell’s chromosomes, it is responsible for regulating almost all forms of cellular activities. Every cell is categorized based on the presence or absence of the nucleus. If the nucleus is present in a cell it is called a Eukaryotic cell. If the nucleus is absent in a cell it is called a prokaryotic cell.

Structure of Nucleus

• The nucleus is the most important and functional part of the cell.

• The nucleus is enclosed by the nuclear membranes.

• It is covered by a structure called the nuclear envelope.

• The membrane distinguish the cytoplasm from the contents of the nucleus

• The cell’s chromosomes are also cramped within the nucleus.

• DNA is present within the chromosomes, it provides the genetic information for the creation of different cell components including reproductive cells.

Compartmentalization of the Cell

The nuclear envelope gives a definite structure to the eukaryotic nucleus and separates the contents from the rest of the cytoplasm that encloses the nucleus. The nuclear envelope prevents the translation of unspliced mRNA by separating the nuclear process from the cytoplasmic process.

Gene Expression

DNA transcription occurs in the nucleus. DNA transcription involves the unwinding of DNA double helix, synthesis of RNA, the coiling of DNA, and the actual transcription process. 

Nuclear Transport

Transporting various molecules in and out of the nucleus through the nuclear pores is an important function of the nucleus. Important proteins are carried into the nucleus with the help of importins. Molecules like the RNA are transported out of the nucleus with the help of exports. 

Assembly and Disassembly

During cell division, the nucleus is integrated and disintegrated to divide the contents and the genetic material. The cell nucleus is also associated with programmed cell death or apoptosis. The nuclear lamina and the nuclear envelope dissolve and then form again during the cell cycle. Duplication of the DNA and RNA replication takes place in the nucleus. Thus, the nucleus integrates and disintegrates various structures during different phases of the cell cycle. 

Pre-mRNA Processing

Before getting transported to the cytoplasm, the primary transcript, or the newly synthesized mRNA go through post-transcriptional modification. This happens inside the nucleus and involves a series of biological processes.

Ribosome Biogenesis

A part of ribosome biogenesis takes place in the nucleus. Over 200 different proteins work in coordination to synthesize the four eukaryotic rRNAs, which then together with the ribosomal proteins synthesize the pre-40S subunit and the pre- 60S subunit. These subunits are then transported to the cytoplasm for maturation. 

Functions of Nucleus

Following are the important nucleus function:

• It contains the genetic information of the cell and controls the growth and reproduction of the cell.

• It not only stores DNA but also acts as a home of some important cellular processes.

• One’s DNA in the nucleus can be duplicated. This process is called DNA Replication and It can produce DNA’s identical copy.

• The first step of cell division is the Production of two identical copies of the body, where every new cell will get its own instructions.

• Secondly, the nucleus is the site of transcription that creates various types of RNA from DNA. Transcription is similar to creating copies of the human body’s instructions which are moved out and read by the other cells.

• The most important rule of biology states that DNA is copied to RNA, and then proteins.