Nucleus: Definition, Structure And Function

 The nucleus is the largest organelle in the cell, found in all eukaryotic cells, but the cells of the phloem vessels adult and adult mammalian red blood cells. Core shapes are generally round to oval with a diameter of ± 10 μm (micro meter) and a length of ± 20 lm. Generally, each cell has only one core, but there are also organisms that have more than one core. For example, Paramecium which has two cores, the micronucleus and macro nucleus.


The nucleus has a very important role for cell life, because it serves to control all activities of the cell. This is because the cell nucleus contains the genetic information in the form of DNA (deoxyribonucleic acid). DNA is able to replicate (make copies of themselves), followed by nuclear division. Thus, duplicate core contains the same DNA as the parent. Encased by a membrane nucleus and the nucleus containing chromatin, one or two nucleoli, and nucleoplasm. Core membrane consists of two layers of membrane. Deal directly with the outer membrane of the endoplasmic reticulum, the endoplasmic reticulum covered by the ribosome and is involved in protein synthesis. At the core there is a membrane pores that allow the exchange of substances between the nucleus and the cytoplasm, such as the release of RNAd (ribonucleic acid ambassador), the entry of ribosomal proteins, nucleotides, and DNA molecules which regulate activities.


Nucleoplasm contained in the nucleus or core gum gel. Nucleoplasm containing various chemical substances, such as ions, proteins, enzymes, and nukleotid. Chromatin is composed of DNA strands attached to the protein basis. Chromatin means colored material, because it is easy to absorb the colors that can be seen under a microscope. In the process of cell division, chromatin intensively absorbing dyes so that more easily seen. Yarn chromatin constrict (shortened) resembles a twisted yarn called chromosomes. Nucleoli have a spherical shape, contained in the nucleoplasm which serves in making RNA. In addition, the nucleolus contains a lot of DNA that act as organizers of the nucleus and contains copies of the genes encodes ribosomal RNA. Nucleoli will dissolve and did not appear again in the prophase (initial level in the process of cell division) and will be made again by the organizers at the end of cell division (telophase).

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