The Nucleus of the Cell
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.
FAQs on Eukaryotic Nucleus
1. Give some Important Notes on the Nucleus?
The nucleus is a specialized double-bound structure or organelle.
It acts as the control center of the cells.
It is the characteristic part of eukaryotic cells which is absent in prokaryotes like bacteria and viruses.
It contains all the genetic material of organisms.
Most of the eukaryotic cells have one nucleus but some cells may have more than one nuclei. For example, Paramecium.
Some eukaryotic cells even lack a nucleus. For example mature red blood cells or erythrocytes.
The nucleus has different sizes depending upon the cell type.
Most of the nuclei are spherical but in leukocytes, multilobed nuclei are also possible.
2. Are Chromatin and Chromosomes the Same?
Chromatin and chromosome are basically the same, but the only difference is that the chromosomes are more condensed than chromatin.
The duration of chromatin condensation depends and varies depending on the cell cycle phases.
Most of the chromatin is not condensed during interphase.
There are generally two types of chromatin that are based on condensation. They are:
Euchromatin: It has clear evidence of lesser condensation, it is light staining. This is transcriptionally active as there is space available for enzymes to work upon.
Heterochromatin: There is much more evidence for condensation, it is dark staining and transcriptionally inactive.
3. What is a Chromosome?
A thread-like structure in which DNA is compactly packaged inside the nucleus is called a chromosome. The DNA is coiled around with a protein substance called histones, which provides structural support. Chromosomes guarantee that during cell division, DNA gets cloned and distributed appropriately. Each chromosome has a centromere, which disintegrates the chromosome into two sections – the p (short) arm and the q (long) arm. The centromere is located at the constriction point of the cell, which may or may not be the center of the chromosome.
4. What is DNA?
Deoxyribonucleic acid (DNA) has the hereditary material of the cell which consists of instructions for development, growth, and reproduction. DNA is carried through generations in humans and many other organisms. The DNA is similar and it is located in almost all the cells of the human body. DNA is generally located within the chromosomes of the nucleus, but in a few cases, DNA is also found in the mitochondria. Chromosomes consist of DNA, which is coiled around histones (alkaline proteins). If the DNA is extended, it would measure approximately 2 meters in length.
5. What are the Types of Organelle in Eukaryotic Cells?
Types of organelles include
Endoplasmic Reticulum – helps in sorting, processing, and transporting protein and lipid molecules. It is the largest organelle of the eukaryotic cell.
Golgi Apparatus – compact molecules (such as proteins and lipids) processed by the endoplasmic reticulum and carried out of the cell.
Mitochondrion – converts food into energy that the cell can use and synthesizes adenosine triphosphate by a process called oxidative phosphorylation. Mitochondria are the powerhouse of the cell.
Ribosome – creates proteins for use inside and outside the cell.
Lysosome and Peroxisome – digest foreign bacteria in the cell, rid the cell of toxic materials and recycle worn-out cell components. These organelles act as the recycling center of the cell.
