PROKARYOTIC CELL

When we look around our surroundings we observe a variety of organisms. Not only us, even on the surface of the skin or inside your digestive or organ tract, but a huge number of different microorganisms also reside there. This is how we are home to approximately 100 trillion bacterial cells and structures.

We can infer that our body is acting as an ecosystem. 

The surroundings and nature consist of both prokaryotic and eukaryotic cells. 

All the cellular structures can be categorised into these two broad segments. The domains-  Bacteria and Archaea (consists of unicellular organisms) are put under prokaryotes. The term pro refers to ‘before’ and Kary refers to the nucleus. Eukaryotes are animals, protists, fungi and plants. The word ‘EU’ refers to true.

PROKARYOTIC CELL

A prokaryotic organism can be defined as a  once which are single-celled organisms that are devoid of membrane-bound organelles and the nucleus. The word prokaryotes are derived from the Greek word (pro, ‘meaning before’) and (karyon, meaning ‘kernel’ or ‘nut’). 

• According to the classification of the two-empire system described in the studies of Édouard Chatton, the prokaryotic cells were segmented within the empire Prokaryotic. On the other hand, the three-domain system that is based on the concept of molecular analysis classifies the prokaryotes into two broad parts: Bacteria/ or the Eubacteria and Archaea/ or the Archaebacteria). The Organisms that possess nuclei are placed in a third segment called Eukaryota. It is believed that the prokaryotes have arisen before the eukaryotes as per the theories of the origin of life.
• Besides being devoid of a nucleus, the prokaryotes have neither a mitochondrion nor the various membrane-bound organelles, unlike the eukaryotes that have them all.

• At one point in time, there was an idea that the cellular parts of the prokaryotes were not enclosed, the exception being an outer cell membrane.

• Some prokaryotes, for example, cyanobacteria (being unicellular) can make large colonies. Whereas other bacteria such as myxobacteria comprise multicellular levels in their life spans.
• The prokaryotic cells are asexual, i.e. reproduction in the absence of fusion of gametes. Furthermore, horizontal gene transfer also occurs in prokaryotes.

PROKARYOTIC CELL SIZE

The diameter of a typical prokaryotic cell varies from 0.1 to 5.0 μm (micrometres) in diameter. Unlike the eukaryotic cells, they are quite small as compared to the eukaryotic cells. They have a variation in diameter ranging from 10 to 100 μm (micrometres).

PROKARYOTIC CELL – ITS COMPONENTS

Regardless of whether the cell is prokaryotic or eukaryotic, there are basic key elements required to fit into the structural definition of any cell. All of them have four primary components described below: 

1. The plasma membrane: is an outer layer that differentiates the interior of the cell from the external environment.
2. Cytoplasm: It is filled with cytosol having jelly-like consistency. It also has cellular organelles suspended in the cytoplasm. Talking specifically about the eukaryotes cytoplasm is the region present in the interior of the plasma membrane but outside the nucleus.
3. DNA: Deoxyribonucleic acid is the basic genetic material of the cell.

The major chunk of prokaryotic DNA is found in the central area of the cell termed the nucleoid. The DNA constitutes a single big loop known as the circular chromosome. 

1. Ribosomes: are the molecular factories where there is a synthesis of proteins.

The ribosomes of prokaryotic cells have ribosomes having a sedimentation coefficient of 70S. It can be divided further into two subunits:

• The L subunit/ largest subunit:

Includes a 50S sedimentation coefficient, plus 31 proteins, 5S and 23S rRNA.

• The minor subunit (S subunit):

 It has a 30S sedimentation coefficient and contains 16S rRNA and 21 proteins.

Most bacteria are enveloped by a rigid cell wall case composed of peptidoglycan. It is a  polymer made of proteins and carbohydrates. The type of cell wall containing glycocalyx is present in some prokaryotes only and not all of them. The cell wall is lacking in the prokaryotes like thermoplasma and mycoplasma. 

THE FUNCTIONS PLAYED BY THE CELL WALL

• The cell wall gives an extra layer of protection to the cell structure.
• It aids the cell to maintain shape and contour and prevents dehydration. 
• Many bacteria possess a capsule, which is an outermost envelope made of carbohydrates called the capsule. The capsule has a sticky consistency and helps the cell adhere to surfaces in its surrounding.

WHAT DOES A WELL LABELLED DIAGRAM OF A PROKARYOTIC CELL CONSIST OF?

A well-labelled diagram of a prokaryotic cell consists of the following structures: 

• Plasma membrane
• Cell wall
• Plasmid
• Nucleoid (DNA)
• Pilus
• Cytoplasm
• Ribosomes
• Capsule 
• flagella

CONCLUSION

Our body acts as an ecosystem. The environment consists of both prokaryotic and eukaryotic cells and all the cellular structures can be categorised into these two broad segments. Initially, the prokaryotic cells were segmented within the empire Prokaryotic. On the other hand, the three-domain system that is based on the concept of molecular analysis classifies the prokaryotes into two broad parts: Bacteria/ or the Eubacteria and Archaea/ or the Archaebacteria). The Organisms that possess nuclei are placed in a third segment called Eukaryota. Besides being devoid of a nucleus, the prokaryotes have neither a mitochondrion nor the various membrane-bound organelles, unlike the eukaryotes that have them all.