Cell- the basic unit of life ( Prokaryotic cell) | How its Organelle work?

@sudhanshunath December 29, 2020

 - Prokaryotic Cell
        Prokaryotic cells are primitive and lack a true nucleus. Their genetic is not surrounded by a nuclear membrane and is confined to a particular region known as nucleiod. 
 • Prokaryotic cells are generally smaller than eukaryotic cells. There are four basic shapes for prokaryotic (bacteria) as listed below. 
      1- Coccus 
      2- Bacillus
      3- Vibrio
      4- Spirillum 
 • Though their shapes and sizes vary, all cells possess a common structure. All prokaryotic cells have major components that are discussed below
- Cell Wall
       It forms the outermost layer of the cell. it provides integrity to the cell. It is made up of Peptidoglycon, which in turn is made up of carbohydrates. 
It is absent in mycoplasma. 


- Plasma Membranes ( Cell Membranes) 
       It just lies inside the cell wall. It isolates the cell's content from the outside the environment and forms a barrier to substances entering in and out of the cell. Membranes are semipermeable, meaning they allow only certain substances to pass through it while preventing others. It is made up of Phospholipid bilayer. 


- Cytoplasm
         All of the fluid substances present inside the cell constitutes cytoplasm. It comprises all kind of cell organelles present in a cell, with exception of no nucleus in a prokaryotic cell. 


-  Mesosomes 
        These are formed by the plasma membrane extension into the cell. They help in process, such as cell wall formation, respiration, etc. 


-   Ribosomes
        These are the sites of protein synthesis. Ribosomes are found to be associated with the plasma membrane. They are not bound by any membrane system. 


-   Cytoplasmic Inclusion 
     Inclusion bodies lie free in the cytoplasm. They help in the storage of reserve material, 
for example- phosphate granules. 


Recommend topics :- 


   - Cell Theory 
         Cell theory was proposed by Matthias Jakob Schleiden (1838) and Theodor and was later  modified by Rudolf Virchow. The two main postulates are:
  •All organisms are made up of cells. 
  • Cell is the basic structural and functional unit of life. 
 An important addition to the Cell theory was made by Rudolf Virchow In 1868 l. He stated that a new cells arise from preexisting cell (in latin: omins cellular e cellula). 

  - Size of Cell
       Most of the cells are minute and visible only under the microscope. They are only a few micrometres in diameter. The cells range in size from micrometres to as long as 1 m. There are some cells which are bug enough to be seen with naked eye. For example egg of an ostrich is about 25-cm long and 13- cm wide. 
    
  -  Shape of Cell 
        The shape of the cells varies according to their function. They may be disc like, polygonal, columnar, cuboid or thread like. Nerve cells have elongated structure and this help them in conducting impulses quickly. Similarly, there are cells that have flexible shape, for example, amoeba and some blood cells. The flexibility in amoeba's shape helps it to perform various activities, such as movement, feeding, etc. The change in shape of amoeba is due to the formation of Pseudopodia that are projections on its body. 

  - Types of Cell
         Cells an be divided into two types: prokaryotic and eukaryotic, according to the differences in their cellular organization. 
 • The cells which possess a true nucleus along with Membrane bound organelles are called eukaryotic cells, for example, plant cell and animal cells. 
 • The cells which do not possess a well defined nucleus as well as membrane bound organelles are called prokaryotic cells, for example, bacterial cell. 


   Points to remember
 • A cell the smallest individual units of matter capable of performing all essential life process by itself. 
 • Cell theory was proposed by Matthias Jakob Schleiden (1838) and Theodor Schwann (1839). 
 • Rudolph Virchow stated that new cells arise from pre-existing cells. 
 • Eukaryotic Cells possess a true nucleus, that is, their genetic material is surrounded by a nuclear envelope and membrane-bound organelles, example, plant cell. 
 • Prokaryotic cells are primitive type of cells which lack a true nucleus and membrane -bound organelles. 
 


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