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Prokaryotic Cells

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  • Last Updated : 30 Nov, 2022
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The cell is the smallest unit of a living entity, the cell is the foundation of all life. There are some species with only one cell, like bacteria. Then there are species with 100 trillion cells or more, like humans. All the different cells have the same chemical composition but they carry because of the expression of different genes according to the environment or requirement of the cell.

Definition of Prokaryotic Cells

Prokaryotic cells are those  primitive cells which don’t have a nucleus and membrane-bound organelle.

Characteristics of Prokaryotic Cells

  • Prokaryotic cells lack organelles and have no nucleus.
  • They are significantly smaller than eukaryotic cells
  • Cell wall protects every prokaryotic cell.
  • Many additionally include a polysaccharide-based capsule or slime layer.
  • Prokaryotes frequently have protrusions (protrusions) on their surface.
  • They have single chromosomes due to their simple body and they are primitive ones. 
Prokaryotic Cell

 

Prokaryotic Cells

  •  Pk doesn’t have a nucleus but it contains genetic material. 
  • Cell  Envelope: The cell envelope is a combination of the cell membrane, cell wall, and outer membrane if it is present. Prokaryotes like bacteria exhibit this envelope. It consists of a bacterium’s cell wall and inner cell wall. The integrity of the cell’s structure is provided by the cell envelope.
  • Glycocalyx: Prokaryotic cells are covered in a layer of glycoproteins and glycolipids called the glycocalyx. Although the composition varies depending on the species and the environment, all bacteria secrete a glycocalyx. The glycocalyx has a number of functions, including desiccation resistance, nutrition storage, substrate adherence, surface enhancement (biofilm development), and resistance to phagocytosis. Layers of bacterial populations attaching to a substrate (or host cells) that is covered with a typical glycocalyx make up a biofilm.
  • Cell wall: It is below the Glycocalyx and is formed of peptidoglycan. Its work includes giving the bacteria structure and structural support as well as preventing them from bursting or collapsing.
  • Plasma membrane: A prokaryotic cell’s cytoplasm is encased by a lipid bilayer called the plasma membrane. The cytoplasm is physically isolated from the outer world by it. Additionally, the plasma membrane functions as a barrier that regulates what enters and leaves the cell in a selectively permeable or semipermeable manner.
  • Cytoplasm: Cytoplasm in prokaryotes, which are cells without nuclei, is the entirety of the plasma membrane. In both prokaryotes and eukaryotes, the gel-like cytosol, a water-based fluid containing ions, tiny molecules, and macromolecules, is a significant part of the cytoplasm.
  • Ribosomes: 80S ribosomes are found in eukaryotes while 70S ribosomes are found in prokaryotes. RNA makes up around 62% of ribosomes, with proteins making up the remaining 38%. Similarities in the structure of free and bound ribosomes are related to protein synthesis.
  • Flagella: Flagella, which are present in various eukaryotes as well as prokaryotes, are largely used for cell motility. A filament in the prokaryotic flagellum spins to propel the cell forward. A prokaryote may have one or more flagella, which may be confined to one pole or may be dispersed throughout the cell.
  • Pilli: Prokaryotic cells have a small, hair-like structure called pili on their surface. Although they can play a part in mobility, their involvement in adhesion to surfaces, which promotes infection, is a crucial virulence trait.
  • Plasmids: A plasmid is a type of double-stranded, circular, tiny DNA molecule that differs from a cell’s chromosomal DNA. Both bacterial and certain eukaryotic cells naturally contain plasmids. Plasmid genes frequently provide genetic advantages to bacteria, such as antibiotic resistance. 
  • Nucleoid region: In prokaryotic cells, DNA is found in the nucleoid area. The cytoplasm contains the nucleoid, which is without a membrane. In addition to DNA, the nucleoid area also contains RNA and proteins, including enzymes. The histone proteins of the nucleoid are wrapped around the DNA.

Reproduction in Prokaryotes

Prokaryotes can divide in two ways: sexually, and asexually. 

Binary Fission in Amoeba

 

  • Asexually(binary fission): binary fission, also known as asexual body division into two new bodies, When an organism divides into two halves (cytokinesis) through binary fission, it doubling its genetic material, or deoxyribonucleic acid (DNA), with each new organism receiving one copy of DNA.
Conjugation

 

  • Sexual (conjugation): One bacteria can exchange genetic material with another directly through the process of conjugation. One bacterium acts as the genetic material giver during conjugation, and another bacterium acts as the recipient. The fertility factor, or F-factor, is a DNA sequence that is carried by the donor bacterium.

Gram-staining

The basic dye crystal violet is used to first stain the bacteria. Gram’s iodine solution is then used to treat the bacterium. Then, Gram’s decolorizer, ethyl alcohol, and acetone mixture are added. Safranin, a counterstain that is actually a basic dye, is applied last. With this gram-staining method, we classified the bacteria into Gram Positive and Gram Negative bacteria

Gram-Positive Bacteria

  • These are those bacteria that maintain their crystal violet color and leave a purple stain.
  • The numerous thick peptidoglycan layers provide them with a thicker cell wall.
  • After the decolorization process, the stain is retained by peptidoglycan layers.
  • Typically, they release exotoxins.
  • Streptococcus, Staphylococcus, etc. are examples.

Gram-Negative Bacteria

  • Gram-negative bacteria are those that lose their crystal violet color and stain with red.
  • They have a thinner cell wall and no outer membrane.
  • It is made up of thin layers of peptidoglycan.
  • Endotoxins are typically produced by them.
  • Gram-negative prokaryotes, including Escherichia coli and Salmonella.

Examples of Prokaryotes

  1. Archaea Cells: These are similar to normal bacteria, but they can survive or be found in harsh conditions because of the composition of the surface layer.
  2. Cyanobacteria: These are the Photosynthetic prokaryotes. They have chlorophyll inside and they can do photosynthesis and make their own food. In the aquatic environment, they are the Primary producer.

FAQs on Prokaryotes

Question 1: What are the components of prokaryotic cells? 

Answer:

These are the components of prokaryotic cells,

  • Cell wall
  • Cell membrane
  • Capsule
  • Pili
  • Flagella
  • Ribosomes
  • Plasmids

Question 2: How do prokaryotic cells divide? 

Answer:

Prokaryotic cells reproduce asexually. The majority of prokaryotic cells divide via binary fission, which produces two daughter cells from each parent cell.

Question 3: The intracellular compartments are not found in which of the following cells?

Answer:

The intracellular compartments are not found in prokaryotes.

Question 4: What are examples of prokaryotes? 

Answer: 

Prokaryotes are blue-green algae, bacteria, and mycoplasma. Among prokaryotes, bacteria are the most common. 

Question 5: What kind of cell is referred to as a prokaryotic cell?

Answer:

Prokaryotes are organisms without a nucleus or other organelles in their cells. The bacteria and the archaea are two separate categories of prokaryotes.


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