Why are human bodies asymmetrical? - Leo Q. Wan

Prevodilac: Milenka Okuka Lektor: Mile Živković

Symmetry is everywhere in nature,

Simetrija je prisutna svuda u prirodi

and we usually associate it with beauty:

i obično je povezujemo s lepotom:

a perfectly shaped leaf,

list savršenog oblika

or a butterfly with intricate patterns mirrored on each wing.

ili leptir raznolikih šara preslikanih na oba krila.

But it turns out that asymmetry is pretty important, too,

No, ispostavilo se da je asimetrija takođe izuzetno važna

and more common than you might think,

i uobičajenija nego što biste mislili:

from crabs with one giant pincer claw

od kraba s jednim džinovskim kleštima

to snail species whose shells' always coil in the same direction.

do vrsta puževa čije se školjke uvek uvijaju u istom pravcu.

Some species of beans only climb up their trellises clockwise,

Neke vrste pasulja se jedino penju pritkama u smeru kazaljke na satu,

others, only counterclockwise,

druge to rade u suprotnom smeru,

and even though the human body looks pretty symmetrical on the outside,

a iako ljudsko telo izgleda prilično simetrično spolja,

it's a different story on the inside.

potpuno je drugi slučaj u unutrašnjosti.

Most of your vital organs are arranged asymmetrically.

Mnogi vaši vitalni prgani su raspoređeni asimetrično.

The heart, stomach, spleen, and pancreas lie towards the left.

Srce, stomak, slezina i pankreas su nagnuti ulevo.

The gallbladder and most of your liver are on the right.

Žučna kesa i veći deo jetre su desno.

Even your lungs are different.

Čak su i vaša pluća nejednaka.

The left one has two lobes, and the right one has three.

Levo krilo ima dva režnja, a desno tri.

The two sides of your brain look similar, but function differently.

Dve strane vašeg mozga izgledaju slično, ali imaju različite funkcije.

Making sure this asymmetry is distributed the right way is critical.

Od izuzetne je važnosti da ova asimetrija bude pravilno raspoređena.

If all your internal organs are flipped, a condition called situs inversus,

Ako se svi vaši unutrašnji organi preokrenu nastaje oboljenje situs inversus

it's often harmless.

koje je često bezazleno.

But incomplete reversals can be fatal,

Međutim nepotpuna preobraćanja mogu da budu fatalna,

especially if the heart is involved.

naročito u slučaju srca.

But where does this asymmetry come from,

No, odakle potiče sva ova asimetrija,

since a brand-new embryo looks identical on the right and left.

s obzirom na to da novi embrion izgleda identično s obe strane.

One theory focuses on a small pit on the embryo

Jedna teorija se usredsređuje na maleno udubljenje na embrionu

called a node.

koje se zove čvor.

The node is lined with tiny hairs called cilia,

Čvor je okružen sićušnim dlakama, nazvanim cilije,

while tilt away from the head and whirl around rapidly,

koje se naginju od glave i brzo se obrću,

all in the same direction.

sve u istom smeru.

This synchronized rotation pushes fluid from the right side of the embryo

Ovo sinhronizovano obrtanje gura tečnost s desne strane embriona

to the left.

u levu.

On the node's left-hand rim,

Na desnom obodu čvora,

other cilia sense this fluid flow

druga cilija oseća ovaj protok tečnosti

and activate specific genes on the embryo's left side.

i aktivira naročite gene sa embrionove leve strane.

These genes direct the cells to make certain proteins,

Ovi geni naređuju ćelijama da proizvode određene proteine

and in just a few hours,

i samo za nekoliko sati,

the right and left sides of the embryo are chemically different.

desna i leva strana embriona su hemijski različite.

Even though they still look the same,

Iako i dalje izgledaju isto,

these chemical differences are eventually translated into asymmetric organs.

ove hemijske razlike će vremenom da pređu u asimetrične organe.

Asymmetry shows up in the heart first.

Asimetrija se prvo primećuje na srcu.

It begins as a straight tube along the center of the embryo,

Ono nastaje kao ravna cevčica u središtu embriona,

but when the embryo is around three weeks old,

ali kad embrion ima oko tri nedelje,

the tube starts to bend into a c-shape

cevčica počinje da se savija u obliku slova c

and rotate towards the right side of the body.

i rotira se prema desnoj strani tela.

It grows different structures on each side,

Razvija različite strukture na obje strane,

eventually turning into the familiar asymmetric heart.

vremenom se pretvarajući u poznato asimetrično srce.

Meanwhile, the other major organs emerge from a central tube

U međuvremenu, drugi značajni organi se razvijaju iz centralne cevčice

and grow towards their ultimate positions.

i rastu prema svojim konačnim pozicijama.

But some organisms, like pigs, don't have those embryonic cilia

Međutim, neki organizmi, poput svinja, nemaju ove embrionske cilije,

and still have asymmetric internal organs.

a i ipak imaju asimetrične unutrašnje organe.

Could all cells be intrinsically asymmetric?

Da li je moguće da su sve ćelije prevashodno asimetrične?

Probably.

Verovatno.

Bacterial colonies grow lacy branches that all curl in the same direction,

Bakterijske kolonije razvijaju mrežaste ogranke koji se savijaju u istom smeru,

and human cells cultured inside a ring-shaped boundary

a ljudske ćelije nastanjene unutar prstenastih ograničenja

tend to line up like the ridges on a cruller.

poravnavaju se poput ivica kuglofa.

If we zoom in even more,

Ako još malo zumiramo,

we see that many of cells' basic building blocks,

videćemo da su mnoge gradivne materije ćelija,

like nucleic acids, proteins, and sugars, are inherently asymmetric.

poput nukleinske kiseline, proteina i šećera - prevashodno asimetrične.

Proteins have complex asymmetric shapes,

Proteini imaju složene asimetrične oblike,

and those proteins control which way cells migrate

a ti proteini određuju kuda će ćelije da migriraju

and which way embryonic cilia twirl.

i na koju stranu će embrionske cilije da se uvrću.

These biomolecules have a property called chirality,

Ovi biomolekuli imaju svojstvo zvano kiralnost,

which means that a molecule and its mirror image aren't identical.

što znači da molekul i njegov odraz u ogledalu nisu identični.

Like your right and left hands, they look the same,

Poput vaše desne i leve ruke, one izgledaju isto,

but trying to put your right in your left glove proves they're not.

ali pokušaj stavljanja desne u levu rukavicu dokazaće suprotno.

This asymmetry at the molecular level is reflected in asymmetric cells,

Asimetrija na molekularnom nivou se odražava na asimetrične ćelije,

asymmetric embryos,

asimetrične embrione

and finally asymmetric organisms.

i konačno na asimetričan organizam.

So while symmetry may be beautiful,

Pa, iako je simetrija možda lepa,

asymmetry holds an allure of its own,

asimetrija ima sopstvenu privlačnost,

koja počiva u njenim ljupkim spiralama,

found in its graceful whirls,

its organized complexity,

u njenoj uređenoj složenosti

and its striking imperfections.

i upečatljivim nesavršenostima.