Activation energy: Kickstarting chemical reactions - Vance Kite

235,767 views ・ 2013-01-09

TED-Ed


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Transcriber: Andrea McDonough Reviewer: Bedirhan Cinar
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Right now, trillions of chemical reactions
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are humming away in the cells of your body.
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You never feel them,
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but without these reactions,
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you wouldn't be alive.
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Unfortunately, each of those reactions needs some help.
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You see, most molecules are stable,
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they are happy just the way they are.
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The atoms in them are all bound-up and friendly with one another
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and would prefer to stay that way.
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The problem is, for a chemical reaction to happen,
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the atoms that make up those stable molecules
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need to break away from their friends
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and go buddy up with another atom.
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This break-up is where the molecules need a hand.
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This initial kick-start is known as activation energy.
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It's used to destabilize the molecule,
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to push the bonds between the atoms
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to a place where they are ready to break.
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This unstable state is known as the molecule's transition state.
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Once a transition state has been achieved,
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the atoms become willing to leave their current molecular friends
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and go make new friends elsewhere.
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Once they are convinced, it's a piece of cake.
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Bonds break,
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atoms rearrange,
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and the rest of the reaction happens automatically.
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After that first push, the body doesn't need to put in
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any more energy to help the reaction along.
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Left alone, most of these reactions would be very slow
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because it takes quite a while to build up
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the activation energy the molecules need to get started.
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Enter the enzyme.
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Enzymes are proteins that speed up,
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or catalyze, reactions
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by lowering the activation energy.
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They make it easier for the molecule,
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also known as a substrate,
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to get to the transition state.
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You can think of a reaction like a race.
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Some racers are running along,
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while others have teammates to help them.
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Meet Sam the Substrate.
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His team is the MODS Squad.
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Together, his team is able to get to the finish faster,
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using less energy.
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There are four special enzymes in Sam's team.
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Each has a different strategy
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for lowering the energy it takes to get going
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and speeding up the pace to get the MODS to the finish line.
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The "M" stands for "microenvironment".
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This enzyme creates a tiny, special environment for the substrate,
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resulting in a faster reaction time.
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He runs ahead of the pack,
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flattening out bumps in the road
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and misting cool water on his team of molecules.
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"O" is for "orientation".
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Sometimes two molecules must be positioned
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just right before they will react.
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Like a friend at the finish line,
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the O enzyme provides his molecules
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with specially shaped spaces
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that allow the substrates to interact in just the right way.
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"D" stands for "direct participation".
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Every now and again, a little muscle is needed.
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And when his teammates are struggling to finish the race,
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Teammate D is there to pick them up
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and carry them over the line.
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Finally, "S" is for "straining bonds".
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This guy pushes the team
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through some serious flexibility exercises:
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splits,
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lunges,
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backbends,
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the works.
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Sometimes his substrate teammates
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just need to be stressed and flexed
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into their transition state.
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So that's it.
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Remember that all reactions need energy to get going.
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This energy is known as the activation energy.
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Enzymes lower that activation energy
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and speed the reaction through team MODS:
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microenvironment,
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orientation,
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direct participation,
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and straining bonds.
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