Question

Why is it important to be aware of the differences between prokaryotic cells and eukaryotic cells when using prokaryotic models to study eukaryotic cellular processes or molecules?  

Answer 1

During the course of evolution some of the processes were highly conserved and some became divergent. Thus, general molecular mechanisms of many of the processes at a fundamental level remain similar. But one should keep in mind that the processes though similar may not be the same. This is because during evolution eukaryotic cells became organellar bound and thus processes became compartmentalized leading to bigger and complex cells. The differences can be classified into the following points:

1) Genetic Complexity - Prokaryotes as a starting level act as a blueprint for these processes to occur. For example, in DNA replication, the basic principle remains the same, the DNA has to unwound, the strand have to be clamped, and one is a leading strand and other a lagging strand. However, if you compare molecularly, since eukaryotic DNA content is much higher, thus the complexity involved in replicating this huge molecule changes,and more number of molecules are now required for the same process.

2) Size-- Cell biological porcesses such as study of cytoskeleton in prokaryotes has to deal with cells which are small, thus conceptually, the polymerization/ depolymerization etc can be studied but these effects and the forces involved etc can be studied, but these will be at a smaller scale as prokaryotic cells are much smaller as compared to eukaryotic cells.

3) Environmental differences-- prokaryotes in general can stay at much harsher environments as compared to eukaryotes. This is because of their smaller size and speical proteins/genes dedicated for such processes. Thus this can lead to variations.

4) Sexual dimophism-- Eukaryotic cells have sexual reproduction in them, which cannot be studied in prokaryotes. The sexual reproduction leads to genetic variation which cannot be studied in prokaryotes.

5) Organellar complexity-- Inter-organellar interactions, such as between mitochondria and nucleas to maintain the energy status of the cell can not be studied in prokarotic cells as organelles came into existence in eukaryotic cells.Thus complexities arising due to these have to be considered.