Goddard Glossary: Chirality

Narration: Katy Mersmann

Transcript:

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Chirality. Are you

right- or left-handed?

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And did you know that some building blocks of life have an answer to that question, too?

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Amino acids are molecules

that make up proteins.

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All living things on

Earth rely on them.

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Many amino acids come in

two mirror image versions

that can't be superimposed.

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To get a sense of this,

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put your hands palms

down and then try to

cover one with the other.

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See how your thumbs still

point in opposite directions?

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This handedness is chirality, and it can be found in molecules too.

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So who cares if amino acids are north or south paws?

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Well, it affects how

they interact with

life. On Earth,

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life produces almost exclusively left-handed amino acids and right-

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handed sugars.

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But no one knows when or how that convention got started.

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One theory is that the

solar system predominantly

made left-handed

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amino acids before life

began, and life just followed suit.

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To find out, we recently sent a spacecraft

called OSIRIS-REx to

an asteroid called

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Bennu to collect samples of

early solar system material

and bring them to Earth.

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Astrobiologists found

amino acids in the

rocks from Bennu,

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but they weren't

all left-handed.

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They were evenly split, about half left-handed

and half-right.

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This suggests that early Earth might have had

a more equal mixture

of left- and right-

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handed amino acids, too, and something about life turned things to the left.

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Scientists are just

beginning to study

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the Bennu samples and are already asking new questions.

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Sometimes getting the right

data means you're left with

an even bigger mystery.