Q. 19

Name the three major functional regions of cells. Briefly mention the components of each and explain the function of each.

Answer :

The cell has three major functional regions:
(a) Cell Membrane
(b) Nucleus
(c) Cytoplasm

(a) Cell Membrane – The outermost layer which regulates the inflow and outflow of various substances of a cell is the cell membrane. It is also known as the plasma membrane. Its main function is to surround and protect the cytoplasm of the cell. The membrane is made of phospholipids bilayer having protein and carbohydrate molecules infused within the lipid bilayer. This fluid-structure provides enough mechanical support and flexibility to allow cells to grow and move. The cell membrane acts as a gate which allows only certain molecules into or out of the cell.
(b) Cytoplasm – It is the jelly-like component within the cell and is mostly composed of water along with various nutrients required by the cell. It provided the enriching environment within the cell for several metabolic reactions to occur systematically.
It serves various functions within the cell:
  • It provides mechanical strength to the cell by exerting turgor pressure against the cell's membrane thus maintaining the shape of the cell.
  • It is the place for the functioning of most regulatory activities like metabolism, cell division, and protein synthesis within the cell.
  • The cytoplasm contains organelles called ribosomes which do protein synthesis.
(c) Nucleus – The nucleus is also known as the master of the cell. It contains the code of life within itself, i.e. DNA (Deoxy-ribonucleic acid) which codes the genetic information of the cell. It is present in the eukaryotic cell but is absent in prokaryotic cell. Instead, prokaryotic DNA is freely lying in the cytoplasm in a region called nucleoid. It is separated from its surrounding cytoplasm by the nuclear membrane. Also, this membrane has certain small pores which regulate the exchange of materials like protein, RNA, etc between the cytoplasm and nucleus. It has chromatin material within the cell consisting of thin long threads of DNA encircled around protein.
Nucleus performs various functions like:
  • It controls gene expression and facilitates the replication of DNA during the cell.
  • It controls the metabolic reactions within the cell by producing mRNA which codes for enzymes.
  • It is also the site for ribosomal RNA (rRNA) synthesis, which assemble as ribosomes in cytoplasm. They are important for translation of proteins.
  • It is responsible for the transfer of characters from parent to offspring via genetic material (DNA) present inside the nucleus.

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