Essay on Basic Microbiology

Categorising the differences between prokaryotic and eukaryotic cells

Introduction

Cells are the basic unit of life and the first living cells to have evolved on earth were the prokaryotes. Prokaryotes are synonymous to bacteria. The process of evolution gave rise to the more advanced cellular forms known as the eukaryotes which are the building blocks of plants and animals. It was the attainment of complex characteristics by the prokaryotic cells to perform advanced function that led to the evolution of eukaryotic cells billions of years following appearance of prokaryotic cells.1 Since, certain bacteria are known to be pathogenic to humans, it is important to understand the differences between the two to direct drugs for better therapeutic results.

Differences between Prokaryotes and Eukaryotes

Features

Prokaryotic cells

Eukaryotic cells

Nucleus

Not membrane bound

Membrane bound

Cholesterol containing plasma membrane

Generally absent

Present

Cell wall

Complex composed of peptidoglycan

Relatively simple without peptidoglycan

Organelles such as mitochondria, chloroplasts, Golgi apparatus, endoplasmic reticulum, lysosomes, peroxisomes

Not seen

Present

Genome

Haploid

Diploid

Exchange of genetic material

Limited by unidirectional transfer

Sexual reproduction involves formation of gametes and crossing over of genes

Ribosomes

Small

Large

Table : List of the differences between prokaryotes and eukaryotic cells2

The differences in prokaryotic and eukaryotic cells are important from pharmacological point of view. Antibiotics have to be formulated in such a way that they are selective in their action of targeting pathogenic bacteria without affecting the host eukaryotic cells. Antibiotics can be directed towards the cell wall synthesis. As the eukaryotic cells lack cell wall, these drugs will specifically destroy bacterial cells. Penicillin inhibits the formation of peptidoglycans which leaves bacteria with a susceptible cell wall. Since human or animal cells do not need peptidoglycans, the host cells are saved. The synthesis of proteins is a simpler and faster process in the prokaryotes. The mRNA is translated simultaneous with their manufacture due to absence of membrane bound nucleus. Certain antibiotics inhibit the protein synthesis by binding to the subunits of ribosomes. Antibiotics such as tetracyclines can thus hinder the protein synthesis. Since eukaryotic cells have a more complex and elaborate process of protein synthesis, similar consequence is not seen with tetracycline accumulation in the host cell. Antibacterial selectivity can also be achieved by targeting nucleic acid synthesis. Both eukaryotic and prokaryotic cells have different set of enzymes that may be targeted to inhibit enzyme function. Drugs like rifampin target transcription by affecting elongation of RNA while others like quinolone exert their lethal action by their action on DNA gyrase. This enzyme is vital for DNA replication. If the nuclear material is not duplicated, the cell multiplication is repressed. Similar result on inhibition on DNA replication can also be achieved by metabolites of drugs such as metronidazole. Similarly, if the crucial metabolic processes are hampered, the bacterial cell is unable to survive in a host. E.g. Inhibition of folic acid pathway by sulphonamides. As humans cannot synthesize folates, the harmful action of the drug is averted.3,4

Conclusion

Thus, it is imperative to understand the basic and molecular differences between the prokaryotic and eukaryotic cells so as to apply this knowledge for the ultimate benefit of humans.

References

  1. Cooper GM, Hausman RE. A molecular approach. The Cell. 2nd ed. Sunderland, MA: Sinauer Associates. 2000.
  2. Willey JM, Sherwood L, Woolverton CJ. Prescott, Harley, and Klein's microbiology.
  3. Xie Y, Dix AV, Tor Y. Antibiotic selectivity for prokaryotic vs. eukaryotic decoding sites. Chemical Communications. 2010;46(30):5542-4.
  4. Ullah H, Ali S. Classification of Anti-Bacterial Agents and Their Functions. Antibact. Agents. 2017 May 31.

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