Every living cell has centrally placed circular and dusky structure called “nucleus“. The nucleus function is key to a cell’s normal survival. The cells with a well formed nucleus are called as eukaryotic cells. The cells lacking this nucleus are called prokaryotic cells. It is also absent in red blood cells and hence are called as corpuscles. It appears as a spherical body when viewed under a microscope. The nucleus is the largest organelle of the cell visible under the microscope. Nucleus is believed to have central control over the entire cell and other cell organelles through out its life span. It contains large amounts of DNA, chromatin material which are the genes.
Structure of nucleus: It is spherical in appearance in most case while, it can also have many shapes i.e polymorphic. It looks dense and thick under a microscope.
The nucleus has a double membrane nuclear membrane enclosing the entire nuclear contents. As shown in the picture, there is outer nuclear membrane (ONM) and inner nuclear membrane (INM). It also has nucleoplasm (i.e fluid matrix of nucleus), DNA, chromosomes, nucleolus. On the membrane there are few nuclear pores for connection with external cytoplasm.
Nucleus function & importance:
♣ The pores on the nucleus help in the transfer of formed mRNA from nucleus into the cytoplasm. While amino-acids and other substances required for DNA, RNA etc. formation move from cytoplasm into nucleus.
♣ Steroid and other drugs act by regulating the genes in the nucleus by fixing onto the receptors on nuclear membrane.
♣ Nucleus forms the mRNA by which it guides the protein synthesis required for cell physiology, growth, multiplication, death etc.
♣ Cell division is an important nucleus function. It initiates the process by DNA, nucleus and also cell membrane divisions.
♣ The genes determine the characteristics of the cell’s proteins, including the structural proteins, as well as the intracellular enzymes that control cytoplasmic and nuclear activities.
♣ The genes also control and promote reproduction of the cell itself. The genes first reproduce to give two identical sets of genes; then the cell splits by a special process called mitosis to form two daughter cells, each of which receives one of the two sets of DNA genes.