The Earth formed from stellar gases that eventually formed the solid structure we now know. Stellar, or star (like the Sun) masses are massive fusion reactors emitting different forms of energy. Fusion refers to the process whereby two atoms collide and form a new atom, with energy released in the process. Two Hydrogen atoms can come together and form Helium, for example.
In this way more and more complex atoms are formed, and one of the atoms formed in the stellar nursery is Carbon. Without the carbon born of the chaotic energies in the stars, life on the Earth as we know it would not exist.
It was on this early Earth, a sordid, spinning mass wracked by electrical storms, blazing hot magma and constant upheaval that life was born. But even before life there was carbon.
Carbon has an unique electrochemistry which makes it the perfect building block of larger structures. Almost every single molecule in your body has carbon in it. It is the key atomic component of life.
Carbon atoms are like little balls with 4 sticky nubs that rotate freely around the center. They can attach themselves together in lots of different shapes and to lots of other elements. Carbon forms many different and stable molecular structures. A very useful quality in a building block. And quite unique among the elements of the periodic table.
One of the things these incredible, beautiful and flexible stickyballs naturally form are chains of other carbon-based molecules. And chains of carbon atoms, in the form of hydrocarbons, are the basis for all life on our planet.
The first thing life had to do was escape from it's own turbulent surroundings. If you are a hydrocarbon molecule, a stray ion could destroy or alter your structure. So one of the first things life had to accomplish was homeostasis.
It needed a barrier to prevent the outside world from getting in. A gate preventing miscreants from spoiling the party inside while allowing honoured guests entrance.
While little is known about actual protobiont structure, it is very likely that even if they did not exhibit pure homeostasis they did have an internal environment which was different from the external environment. A way of protecting what was inside from the outside.
Currently we know that all cells, including single-cell organisms, use a membrane structure, the cell membrane to ensure the internal environment of the cell is distinct from the outer environment. A lot of organisms also rely on a cell wall as a defense against the evil elements of the world outside. Cell walls were first seen in our lovely ancestors the prokaryotes. Cell walls are different from cell membranes in that they are rigid versus flexible structures.
Regardless, both cell walls and cell membranes allow for the creation of spaces that are safe from the ravages of the raw environment.
With these structures in place, our quest for existence can begin in earnest, but how exactly did life do it?