Why do prokaryotes not develop organelles? Is there a benefit to being more simple if you’re unicellular?


Why do prokaryotes not develop organelles? Is there a benefit to being more simple if you’re unicellular?

In: Biology

Firstly, there are lots of unicellular organisms that do have organelles, as there is a broad diversity of unicellular eukaryotes (probably over 95% of eukaryotic diversity is unicellular).

The most simple answer to why prokaryotes don’t have organelles is that prokaryotes by chance have not evolved the machinery to generate and maintain organelles.

One particular organelle of note, the mitochondrion, was acquired in a single event where a primitive cell engulfed a particular prokaryote and enslaved it, and the engulfed prokaryote was passed down to all of the descendants of that original cell, eventually evolving into the current mitochondrion. All descendants from that event are eukaryotes.

To answer the last part of your question, some would argue that prokaryotes, lacking a mitochondrion, do not generate as much energy as eukaryotes, so they can’t meet the energy needs to maintain organelles, although this is controversial.

In the most general terms, there is always a benefit to being more simple in that every thing that an organism makes costs energy.

Prokaryotes are unicellular but all eukaryotes aren’t multicellular.

Setting aside if viruses are alive, all life is divided into two groups prokarya and eukarya. Prokaryotes are single celled organisms that have no nucleus, no membrane bound organelles and are much smaller than eukaryotes(less than a tenth of the size on average.) Prokaryotes are bacteria and archea. Most people are familiar with bacteria, archea are organisms that are like bacteria but just as distantly related to bacteria as eukaryotes are. So eukaryotes can be both unicellular and multicellular. Yeast are single celled fungi for example.


Above is a link explaining endosymbiosis which is the theory that organelles came from a cell engulfing another cell but then not digesting it. Basically, organelles were once free living organisms. Chloroplasts (organelle for photosynthesis) were once cyanobacteria.

It might be the case that organelles allow for multicellularity. All eukaryotes have mitochondria (one of those organelles). Mitochondria is where the vast majority of ATP (energy storage molecule of cells) is produced.

Some prokaryotes did develop organelles, but by doing so stopped being what we would label prokaryotes. But not all prokaryotes did, of course. Yes, there is a niche for simpler organisms. For example, cell division can be much faster than for more complex organisms. The fastest known division time in yeast (which was achieved by artificial selection) is about 5 times longer than the fastest known for for bacteria.