Eli5: (This prob sounds stupid) How did life forms come to be on earth? Like, how did something become ‘living’?
In: Biology
A basic chemical reaction might go a bit like this:
A + B = P
You mix two things together (reactants), they combine to make a new thing (product)
How fast this happens depends on a few things like heat and concentration of reactants and the general reactivity of the chemicals involved. Different reactions go at different speeds. Some happen in a matter of moments, others can take years.
So if you’re in chemistry class and you want a reaction to go faster, you might heat up your beaker rather than wait around.
Another way of speeding up a reaction is to add a catalyst. Catalysts are a type of substance that increases the rate of a reaction without themselves being changed.
Enzymes are good examples of catalysts, and you’ll also find them in the catalytic converters on cars.
So your reaction might look a bit like this:
A + B + C = P + C
So you get your catalyst back after the reaction, and it can go on to catalyse (speed up) another reaction. It doesn’t get used up like A and B.
Catalysts are chemicals like everything else, so they too can get formed by chemical reactions. So can you have a catalyst for a reaction that makes a different catalyst?
Yes
But what happens if the catalyst for making the catalyst is itself the same catalyst?
A + B = C (slow)
A + B + C = C + C (fast)
You would quickly end up with a lot of Cs because every C you make helps make more.
So this is what happened in the primordial soup. At some point, a molecule formed that was a catalyst for it’s own creation and started making more. (chemicals don’t have a “choice” whether to react, they just do if the conditions are right)
In a sense, these molecules started competing with each other for those reagents, A and B (in this case the reagents are amino acids). Slight changes to the catalysts made them more efficient or faster or resilient to other chemicals, which in turn meant that more of that particular version of the catalyst was made.
Bit by bit, the catalysts became more and more complex, and started coating themselves in lipids to protect themselves, made systems that only allowed proper reagents through that lipid barrier and developed ways to break down bigger molecules back into amino acids. Millions of years pass and the catalysts have gotten so complex we get the first cells.
Because that is essentially what DNA is. A chemical that catalyses the reaction to make more DNA. Our lifecycle is a bit more roundabout than that now, but in a pure sense it is true. Life makes life. A catalyst that makes more of itself.
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