Explaining how life came about is my favorite thing ever. Chemical evolution is so cool. To start you have to talk about the Urey-Miller experiment.

Explaining how life came about is my favorite thing ever. Chemical evolution is so cool. To start you have to talk about the Urey-Miller experiment. Back in the 1950s these two biochemists did an experiment in which they took a containment chamber, filled it with water, ammonia, methane, hydrogen, and all the things you expect to find on any fledgling planet. All the things you would expect on any new Earths. They put a fire underneath so it would evaporate, go into another container to be zapped with electrodes, cooled, funneled back to the original container and cycles back through. They are simulating the patterns of an early Earth, and simulating all the elements you could find on Earth. You take early simple ingredients, get them hot, get them cold, zapped with lightning and other normal processes. They ran it for a while and when they come back they took samples. To their surprise, the water is no longer clear, but is a gross reddish brown. They test it and find it is now full of amino acids. Amino acids are the things that build proteins and make life happen. That is called chemical evolution. Very simple inorganic ingredients come together via totally natural means and form organic macromolecules. There are 4 macromolecules that make up life. Lipids, proteins, carbs and nucleic acids. Those are the 4 macromolecules that make up everything alive. Each one is a polymer meaning its a molecule that forms a chain. I’ll explain each of these below:

PROTEINS are made of chains of amino acids that fold up on themselves. A chain of amino acids is a primary structure. Then it folds into an alpha helix or a beta pleated sheet called a secondary structure. Then it forms a glob called a tertiary structure. Sometimes some globs come together and thats then a quaternary structure and so on. Thats how proteins work. Proteins make up skin, muscle, bones, and everything like that.
CARBS are sugars. Long chain simple sugars such as glucose or fructose. If you stick them together you get sucrose. A bunch of those together makes a polysaccharide. This makes carbs like starche, cellulose and such.
LIPIDS are fats. You have a twisted hydrocarbon chain that repels water and thats a lipid. There are various kinds like phospholipids where a long hydrocarbon chain comes off it to repel water and on the other end is a phosphorus group that attracts water. This makes a hydrophilic and hydrophobic end. One attracts and one repels water. If you take any lipid like cooking oil for example and put it in water it forms a bubble all by itself. Nobody has to tell it to do that. That’s because a sphere is the smallest possible surface area and is the most energetically protected from the water around it. It would take more energy to make any other shape and the universe is lazy. Everything is always as energetically simple as possible. Lipids that naturally form out of normal stuff under normal circumstances, naturally form spheres. Amino acids which make proteins that naturally form out of natural stuff can get stuck in one of these spheres, and you now have something that practically represents a cell. All this stuff formed by totally natural means and naturally assumes the shape of a sphere can naturally come together and form a cell. You can do this in a jar. Now imagine that on a planet taking place over millions of years.

The Urey-Miller experiment has been redone in different ways many times by putting other things in, leaving some things out, and hundreds of combinations and it just always works. Later, we figured out this happens in hydrothermal vents. They pump out acids and bases. These have proton gradients. Whats that? Well an acid is a chemical with a bunch of extra protons and a base is something that doesn’t have enough and has too many electrons. When they neutralize they give off electrical charges that move one place to the next. This is how your cells make energy today. Mitochondria pass protons across a membrane. This turns a protein called ATP synthesis which makes adenosine triphosphate and thats how our body works. It’s how most cells today work. Where can we find natural proton gradients right now? Hydrothermal vents. Where can we find the building blocks of lipids and proteins? Hydrothermal vents. We can even find amino acids, including all the ones important to life, in space. Just floating on asteroids. They form naturally all by themselves all over. You have the building blocks of life, the thing that makes energy in cells even today happening naturally all by itself in hydrothermal vents and all over the universe. Life then starts all by itself. Now we also have NUCLEIC ACIDS, the 4th macromolecule, which is DNA and RNA. We do debate what came first, but the most common consensus is RNA came first. I also follow the RNA world hypothesis. Let me explain why.

RNA is cool because it isn’t just something that carries information, but it also works as a catalysts to make reactions happen. A catalysts is something that lowers the activation energy of a reaction. It makes a reaction happen easier and faster with less energy. So RNA carries genetic information, it can also make more of itself, and it can make other reactions happen faster. Think about how proteins are made in your body today. It’s like this.

You have mRNA(messenger RNA) that makes proteins happen. How? It goes to a ribosome to be read. What are ribosomes made of? They are made of rRNA(ribosomal RNA), and aren’t membrane bound organelles. In the ribosome something brings over amino acids to make the protein. What brings them over? tRNA(transfer RNA). So when your body makes proteins it uses RNA to tell RNA to use RNA to make a protein. Again, you can do this in a jar. That is why the major consensus is that RNA came first. RNA is something that is so unbelievably useful. Why do we have DNA then? Because once it happened to form DNA was/is really good at long term storage and it’s far more stable meaning it stuck around better. You can divide it, make more of it, pack it into a tight wad and have it twist around proteins called histones to makes a tight rope called chromatin, and then chromatin forms a body called a chromosome. Thats how DNA works. It wraps around proteins, wraps into a thick rope, and those thick ropes form a chromosome. It’s super easy to divide these and split them up.

Is it so hard to believe that some of these naturally forming nucleic acids found their way into a blob of naturally forming lipids? THEN they split, THEN you have 2 sets of chromosomes in a cell THEN cytokenesis happens where actin filaments tighten around the cell in a contractile ring, and remember lipids form bubbles naturally, so once squished together you now have a cleavage furrow that then splits into two seperate bubbles! You now have dividing life out of literally “nothing”. It’s not difficult at all to say that very simple ingredients found all over the universe that naturally form organic molecules by natural processes then naturally stated making more of themselves. You then get a VERY early organism. Something so insanely simple. Not bacteria, that would be unbelievably complex in comparison. Just a very simple membrane, very simple genetic material and very simple proteins. The very basics of all of this. That is what we call LUCA. There was probably a ton of very early life, but LUCA is the one that stuck around. Everything that ever lived past that point is related to LUCA. We have a very clear picture of how everything evolved after that. I can gladly get into that if anyone want me to. I’m an evolutionary biologist so this tickles me all over when I get to explain it.


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