A Cell is a basic structural and functional unit of a living organism on Earth. They are also known as the building blocks of life. All the components that lie within the cell are enclosed by a membrane that is selectively permeable and monitors what moves in and out of the cell. A cell consists of a cytoplasm which takes up a maximum of the cell’s volume inside which all the organelles lie. The most important organelle that lies within a cell is the Nucleus. The nucleus happens to be a place where genetic transcription takes place. It’s not wrong in saying that a nucleus comprises all the genomes of the cell.
A cell is of two types:
Prokaryotic - This does not have a nucleus.
Eukaryotic - This consists of a nucleus.
Eukaryotes are generally multicellular organisms, they can also be single-celled, while prokaryotes are generally single-celled organisms.
The nucleus lies within the cell and is enclosed by a double-layer membrane called a Nuclear membrane that separates it from the rest of the cell. This nuclear membrane of the cell has pores and thus it helps in allowing the movement of large molecules in and out of the nucleus. The main activity of the cell is controlled and regulated by the nucleus of the cell. A nucleus comprises of a Nucleoli which are small structures found within the nucleus and also the nucleus is filled with a gel-like matrix known as nucleoplasm in which all the nuclear components are suspended. The nucleus is a house for the genetic code of an organism. Hence it is not wrong in saying that, it is the main centre of information of a cell.
Each cell comprises of one Nucleus. However, in some conditions, the nucleus within the cytoplasm divides but the cytoplasm itself fails to divide. This leads to the production of more nuclei within a single cell and such cells are called multinucleated. There are some cells in higher vertebrates known as the red blood cells which lose their nucleus upon becoming mature.
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The nucleus serves as a site for transcription. The proteins that lie within the nucleus helps in carrying out this process. The information that lies in DNA is transcribed into mRNA molecules. These mRNA molecules encode the information for one protein. Further, the mRNA molecules move through the nuclear membrane into the cytoplasm where they get translated. The translation is nothing but the synthesis of proteins from RNA.
A Nucleoid lies within the prokaryotic cells. These are irregularly shaped and contain most of the genetic material of prokaryotic cells similar to that of the nucleus of eukaryotes. Unlike the chromosome of the eukaryotes, the chromosome of the prokaryotic cell is circular and very large in length when compared to the dimension of the cell. For it to fit inside the nucleoid, it needs to be compacted. The Nucleoid is not surrounded by any membrane-like how a nucleus is surrounded by a nuclear membrane. Hence, it comes in contact with the cytoplasm directly.
Nucleoid is found in single-celled organisms like bacteria and archaea in which the other organelles present in the cell are also not surrounded by any membrane.
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Just like the Nucleus, the Nucleoid is responsible for controlling the activity and reproduction in cells. It is the place where the transcription takes place and also DNA replication takes place in Nucleoid. There is the presence of enzymes within the Nucleoid that behave as the catalyst and aid in the process of replication. It helps in the growth of the cell as well as regulates all of the genetic material of the cell.
1. What is Nuclear Lamina?
Ans: When it comes to animal cells, the nucleus is provided with mechanical support by intermediate filaments. The nuclear lamina is in the form of a meshwork made up of a protein called the lamin protein that lines the inner surface of the nuclear envelope becoming a part of the nuclear skeletal network thus providing structural support to the nuclear envelope. The lamin protein just like other proteins is synthesized in the cytoplasm and later gets transported to the inside of the nucleus.
2. What is the Function of Nucleoid Associated Proteins (NAPs)?
Ans: The NAPs are responsible for the organization of the Nucleoid and they also help in the expression of genes. The NAPs are low molecular polypeptides that are responsible for binding DNA and is capable of altering its shape and further leads the DNA in participating in the process of transcription. The NAPs also can remodel the structure of a Nucleoid.