What is the maximal possible size of a single cell organism? Why can’t a single cell be the size of a coin for example?
In: Biology
Well, there are plenty of large single celled organisms. Many are algae, but some, like Gromia sphaerica are grape sized amoeba. And they move! 🙂
Whether there’s a maximum size isn’t really known. Since we already know that plants and protists can grow pretty large, let’s focus on animal cells.
The largest single celled animals aren’t much larger than a couple of millimeters. The reason for this may have to do with the chemistry of growth and reproduction.
In order for a cell to metabolize and divide it needs its DNA just about everywhere within its volume otherwise the cell won’t be able to “communicate” the right chemicals where they need to be when they need to be there. That’s why the nucleus of an animal cell is the largest organelle and takes up a good chunk of the cell’s volume.
In order for an animal cell to get larger, its nucleus must grow proportionally. But there’s almost no reason for the nucleus to do this because there’s a finite amount of DNA. So it may come down to the “peanut butter spreading too thin”. If the nucleus becomes too large, it’s possible that the proteins the DNA is synthesizing won’t be in the right locations or right proportions when another organelle needs them, and the cell dies.
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