Difference Between Prokaryotes and Eukaryotes


Prokaryotes and eukaryotes differ in cell structure, chemistry, and evolution. Prokaryotes are among the simplest of life forms and may be the oldest true form of life on Earth. Eukaryotes are thought to have evolved from Prokaryotes over millions and in fact billions of years of time.

In general, eukaryotes can be considered to be plant and animal cells while prokaryotes are bacteria and simpler organisms. Some of the most ancient fossils ever discovered are prokaryotes that were simple enough to survive the changes in climate that occurred over time.

The most basic difference between the two types of cells is that eukaryotes have a cellular nucleus that houses chromosome among other elements and prokaryotes do not have a nucleus and do not have chromosomes but do have a structure that performs the same function as chromosome. The structures are called plasmids.

Plasmids differ in physical shape, size, and chemical makeup from true chromosomes. The mechanism of replication of individual cells is different between prokaryotes and eukaryotes due to the difference in the structure of the genetic material in the two different types of cells.

The number of chromosomes in prokaryotes and eukaryotes is different. Eukaryotes have more than one chromosome and prokaryotes have only one. The prokaryote plasmid is chemically less complex than the chromosomes in eukaryotes. Part of the reason for the lack of complexity in prokaryote plasmids is that the organisms are simpler and require less space to transfer the information necessary for replication.

Prokaryotes and eukaryotes reproduce differently. Eukaryotes reproduce through meiosis that produces cells that have only one half of the necessary chromosomes needed to create a new cell. Two of the cells combine and produce the genetic structure that initiates the development of new cells. This process also includes sexual reproduction in plants and animals.

Prokaryotes reproduce by the transfer of DNA through plasmids, conjugation, or bacterial assisted transduction. Some the DNA of the parent is transferred to a new cell. DNA transfer has been shown to have occurred between simple cells and more complex cells giving rise to the concept that one of the forces that produced the development of higher forms of life was the transfer of DNA.

Prokaryotes do not have distinct membrane separated structures like a nucleus, mitochondria, Golgi bodies, or chloroplasts that are found in plants. The function of the structures is carried out in prokaryotes by regions of localized chemical activity in compartments within the cell.

Vacuoles, flagella, vesicles, and ribosomes are present in both prokaryotes and eukaryotes. The ribosomes in prokaryotes are smaller than those in eukaryotes. Eukaryotes have multiple small flagella while prokaryotes that are mobile have a single flagellum. Prokaryotes are smaller in size than eukaryotes in general. The largest eukaryotes can be 100 micrometers in diameter and the largest prokaryotes are 10 micrometers in diameter.

The cell wall in eukaryotes is usually semi-permeable and chemically simpler than the cell walls in prokaryotes. The advantage of semi-permeability provides the potential for the transfer of chemicals in a directed path at a controlled rate. This is why blood can deliver oxygen to all the cells of an animal’s body and nutrients taken from the Earth are transferred to different types of cells in plants at different rates.

The differences in cell wall structure, composition, chemistry, and permeability have allowed prokaryotes to adapt to more extreme environments than eukaryotes. Eukaryotes have been found thriving in the depths of Antarctic lakes that have been sealed for millions of years and in underwater volcanoes.

The lack of permeability in the cell wall of prokaryotes provides survival advantages to this type of organism. Some bacteria that are still actively producing disease today can be tracked back through millions and millions of years. The present disease bacteria have changed in response to antibiotics. The change is often a change in the shape of the cell wall that prevents an antibiotic from being functional.

Prokaryotes have a smaller volume to surface area ratio than eukaryotes. This difference allows the prokaryotes to grow faster due to a higher rate of metabolism. This difference also allows prokaryotes to reproduce much faster than eukaryotes.

Eukaryotes usually exist in multi-cellular groups or organisms. The advantage of large numbers of cells is a higher level of differentiation in function. Different functions allow organisms to develop a competitive advantage over simpler organisms.

Prokaryotes usually exist as single cells. Some prokaryotes do associate together in groups. This association provides a reproductive advantage, a defense against predators, and can accelerate the exchange of DNA that can lead to the evolution of new species or different characteristics.

The physical genetic structure of both types of cells differs considerably. Prokaryote genes carry more information per unit than eukaryote genes. Most of the genes of animals and plants do not control a specific function that produces a protein or any other chemical or structure. All of the genes in eukaryotes control the production of some type of chemical or structure.

Every gene in eukaryotes is expressed on its own while the expression of any other gene. Prokaryotes require the activation of at least three different sites on a given gene. Eukaryotes do not create messenger-RNA that is necessary for the combination of gene function to occur.

Eukaryotes and prokaryotes differ in structure, genetics, reproduction, chemistry, and life span. Most experts in biology and evolution consider that eukaryotes developed from prokaryotes through simple survival of the fittest and the transfer of DNA between different species of prokaryotes that produced an evolutionary advantage.

Prokaryotes are simpler organisms and that simplicity is one of the advantages that have produced such a large population of bacteria. Many of the prokaryotes are fundamentally necessary for human life. The bacteria that inhabit the human gut are a protection against disease causing species. Humans could not exist without prokaryotes.