How did the first cellular structures evolve?

Ok. Just so you know, I am not a cell biologist! I study evolution. This will probably be rudimentary, although I hope the gist is understandable.

First of all, “cells” existed before DNA did. Their ability to replicate was what necessitated DNA. RNA probably existed first, enabling transcription of specific proteins – DNA later became the “permanent” holder of this information, because it is more stable than RNA.

The first thing that made cells possible is membranes. Molecules called phospholipids have a tendency to form membranes, and membranes are what make cells possible – they create an “inside” and an “outside.” Membranes form spontaneously from phospholipids, and with enough they form bubbles. Different molecules might happen to migrate in and out of these bubbles, making the inside different than the outside. Eventually they might uptake molecules that enabled them to metabolize sugars, and eventually this metabolism could become more complex and become what we would call “cellular machinery” (although the line of when these phospholipid bubbles became what we now call cells is blurry at best). The slow process of gaining machinery capable of doing different processes that work together, and differentiating from other cells, and further compartmentalization of tasks within the cell is what eventually led to something like the modern cell. The capability to form specific proteins from an RNA template evolved first, then the ability to “save” these templates indefinitely in the form of DNA came later.

If any of this was confusing, or you want more details about any step, let me know and I’ll try to remember more. This was like a brain exercise, I haven’t thought about an organism smaller than a fish in a long time! :)

@fireinthepriory I wish I could give you 6 great answers, this is exactly what I was looking for.

@RocketSquid Aw thanks! Glad it made sense. :)

I find this video useful. It explains it better than I can.

GA @fireinthepriory.

Remember too that molecules (combinations of atoms) make up everything around us alive or not. There are different types of molecules and different types of chemical bonds that will hold molecules together to then form different types of relatively larger matter…If you are studying cells for the first time, look at images of bacteria cells first, as they are (while still very complex) much simpler than plant or animal cells. Look at the actual chemical makeup of different parts of the cell. What different types of molecules are in the…cytoplasm for example (water, salt, enzymes (proteins made of amino acid), etc.)?