• Question: Which type of cell evolved first, the eukaryotic cell or the prokaryotic cell?

    Asked by Ana María to Tom, Paul, Natasha, Ildiko, Ester, Eoin on 6 Nov 2017. This question was also asked by 273cesk28.
    • Photo: Natasha Myhill

      Natasha Myhill answered on 6 Nov 2017:

      Another great question. I don’t think that we know for sure, but I believe the idea that eukaryotes evolved from prokaryotes by a process called endosymbiosis. That basically means that one cell ate another cell and a new cell was made! This would explain how eurkaryotic cells developed organelles such as mitochondria, which have their own DNA. If the mitochondia was originally a bacterium, then it is likely there was a new relationship made between the bacterium and the larger cell that worked well for both, so it was favoured during evolution.

    • Photo: Paul McKeegan

      Paul McKeegan answered on 6 Nov 2017:

      I agree with Natasha!

      Prokaryotes must have appeared first. Eukaryotes get their name from having a ‘true’ nucleus containing their DNA, rather than letting it float around exposed within the cell. However, for me, the most impressive part of a eukaryote is the mitochondrion – the little machine which burns fuel to release energy for growth and development. Prokaryotes don’t have mitochondria – they carry out similar tasks of energy release within the main body of the cell, called the cytoplasm. So if a bigger cell ‘ate’ a smaller prokaryote, rather than breaking it down for food, it could have benefitted from the controlled energy release carried out by its little passenger and keep it around for good. Only eukaryotes have mitochondria, and as Natasha said, the popular idea is that the mitochondria we have today are very distant descendants of a bacterium that was eaten by a bigger cell long ago.

      It’s also a good idea to lock up this energy factory away from delicate parts of the cell, like DNA. Releasing energy through respiration constantly releases a small amount of ‘Reactive Oxygen Species’ which are very reactive charged atoms and molecules containing oxygen. DNA is easily damaged by these, and this damage can cause mutations that permanently damage the cell. So keeping the energy factory and the DNA in separate parts of the cell works out very well for eukaryotes and this may be one of the reasons eukaryotes could evolve to form organisms made out of trillions of cells working together.

Comments