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  • Thanks to Brilliant for supporting this whole week of SciShow!

  • 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 actuallykinda 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 towait for

  • itlaxatives.

  • 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 yourmovements a little more comfortable.

  • [Outro:] Thanks for watching this episode of SciShow

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  • {♫Outro♫}

Thanks to Brilliant for supporting this whole week of SciShow!

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細胞是如何獲得膜的(也許)|科學秀新聞 (How Cells Got Their Membranes (Maybe) | SciShow News)

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    林宜悉 發佈於 2021 年 01 月 14 日
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