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For life to evolve on Earth, a bunch of complex organic molecules had to evolve a way to assemble into cells. So how did those proto-cells get cell membranes? Some researchers have a new hunch. Also, scientists are borrowing a trick from cheap laxatives to improve energy storage in supercapacitors.

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Sources:
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Go to Brilliant.org/SciShow to learn more. {♫Intro♫}. For life to evolve on Earth, a bunch of complex organic molecules had to evolve a way to assemble into cells.

That’s not as easy as it sounds. But this week in. Proceedings of the National Academy of Sciences, researchers from the University of Washington think they’ve found a way for things to have come together.

Basically, we know that before life emerged, there were limited ingredients to work with. Stuff like fatty acids, amino acids, salt, and magnesium. And from that limited recipe, somehow, cells came about.

But there are some issues here. All cells are enclosed in membranes derived from fatty acids. But those fatty acid membranes aren’t very stable in the presence of charged particles -- like sodium, chlorine, or magnesium ions.

That pretty much describes the primordial soup that gave rise to the first cells. And what’s more, magnesium ions are required for nucleic acids-- like RNA -- to function. It’s crucial for life.

So how did those proto-cells get cell membranes? There must have been some other molecule in the early oceans that could have kept those fatty acids stable enough to assemble into membranes. So the team turned to another class of molecules from their limited cast of characters: amino acids.

Amino acids are the building blocks of proteins, and scientists think there were 10 specific amino acids floating around those early oceans that led to the very first proteins. The scientists combined these amino acids with a particular fatty acid they think would have been present before the first cells formed, then analyzed the interactions between them. It turns out that all of these amino acids had some kind of interaction with the fatty acid membranes.

They found that water-repelling amino acids like leucine bind easily to fatty acids, while more water-loving ones like serine and glycine protect membranes from the harmful effects of magnesium ions. This was similar to previous research the team had done finding that RNA bases also bind to and stabilize fatty acid membranes. As a result, the researchers proposed a new model for the formation of the first cells: amino acids and RNA bound to fatty acids and stabilized them, which helped them form membranes and led to higher concentrations of amino acids and RNA, which led to more binding.

This potentially explains how cell membranes formed in such an inhospitable environment. But it can also answer another question: why fatty acids, proteins, and RNA started hanging out together in the first place, before life was a thing. You can’t have stable proto-cell membranes without amino acids and RNA bases, they say.

Which means all the ingredients for life actually… kinda needed each other, before they were ingredients for life. The researchers say their next step is to figure out how these building blocks teamed up to create functional cellular machinery. The murky history of life on Earth is getting clearer by the day.

There’s also some news about ionic interactions here in the present day, and it connects two fields you wouldn’t usually think of as going together. are high-capacity energy storage devices that can release a large amount of energy relatively quickly. They’re often used in wind turbines to smooth out the intermittent power supplied by the wind, as well as in the regenerative braking systems of hybrid vehicles. They store the energy that would otherwise be wasted during braking to help the car get going again.

They’re a little bit like batteries, except batteries can store more energy over longer periods of time than supercapacitors, whereas supercapacitors can release energy more quickly than batteries. This week, scientists published a paper in the journal Nature Materials showing a way to improve supercapacitors with a class of chemical that’s similar to — wait for it — laxatives. A supercapacitor is made up of two conductors, or plates, of opposite charge soaked in a liquid called an electrolyte and separated by a thin insulator.

An electrolyte is a liquid that contains ions, which are particles that carry a positive or negative charge. That makes it a good conductor of electricity. The electrolyte contains a uniform mix of positively and negatively charged ions.

When the plates are charged, each one attracts ions of the opposite charge, which in turn attract ions of /their/ opposite charge. That forms a double layer on each plate, and the charge separation stores a bunch of potential energy that the supercapacitor can discharge. Right now, supercapacitors mostly use electrolytes that are either water-based or carbon-based, but both have their drawbacks.

So lately, researchers have been tinkering with electrolytes made of ionic liquids — a liquid made of positively and negatively charged components, a little bit like if table salt were liquid at room temperature. In any electrolyte, the ions kind of go wherever they feel an attraction. But these researchers came up with a tweak that could make ionic liquids more predictable.

That’s where the laxatives come in. The researchers in this new study designed a new ionic compound that’s amphiphilic, which means their molecules have one end that’s polar, or slightly electrically charged, and one end that’s nonpolar. And while ionic liquids are not very familiar materials, researchers in the past have taken inspiration from cheap, widely available laxative compounds.

In those, the water-loving polar end and the lipid-friendly non-polar end work together to lower the surface tension and help poop retain more water, which makes it softer and easier to pass. But in supercapacitors, these amphiphilic molecules arrange themselves in a double layer on each plate automatically. The result is a more ordered lineup of ions, which makes for a more efficient energy storage device.

The researchers say that this means there’s the potential to design specific ionic liquids for specific purposes. Not only could this lead the way to improved supercapacitors in hybrid cars, but it could also come in handy in areas as lofty as space exploration. Which is not bad for a principle that also makes your… movements a little more comfortable. [

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