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Every chicken was once an egg,

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every oak tree an acorn,

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every frog a tadpole.

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The patch of mold on that old piece of bread

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in the back of your fridge,

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not so long ago that was one, solitary cell.

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Even you were once but a gleam

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in your parents' eyes.

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All these organisms share

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the same basic goal:

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to perpetuate their own existence.

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All lifeforms that we've discovered so far

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stay alive by using

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basically the same rules, materials, and machinery.

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Imagine a factory full of robots.

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These robots have two missions:

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one, keep the factory running,

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and two, when the time is right,

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set up an entirely new factory.

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To do those things,

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they need assembly instructions,

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raw materials,

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plenty of energy,

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a few rules about when to work normally,

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when to work quickly,

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or when to stop,

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and some exchange currencies

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because even robots need to get paid.

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Each factory has a high security office with blueprints

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for all the possible factory configurations

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and complete sets of instructions

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to make all the different types of robots

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a factory could ever need.

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Special robots photocopy these instructions

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and send them off

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to help make the building blocks of more robots.

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Their colleagues assemble those parts

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into still more robots,

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which are transported

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to the right location in the factory

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and given the tools they need to start working.

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Every robot draws energy

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from the central power plant,

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a giant furnace that can burn regular fuel

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but also scrap materials

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if not enough regular fuel is available.

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Certain zones in the factory

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have harsher working conditions,

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so these areas are walled off.

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But the robots inside can at least communicate

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with the rest of the factory

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through specialized portals

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embedded directly into the walls.

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And as you've probably figured out,

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what we're describing here

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is a cell.

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The high security office is the nucleus.

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It stores the blueprints and instructions

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as deoxyribonucleic acid, or DNA.

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The photocopied instructions are RNA.

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The robots themselves are mostly proteins

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built from amino acids,

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but they'll often use special tools

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that are, or are derived from,

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vitamins and minerals.

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The walls between factory zones

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and around the factory itself

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are mostly made up of lipids,

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a.k.a. fats.

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In most organisms,

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the primary fuel source are sugars,

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but in a pinch,

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fats and proteins can be broken down

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and burned in the furnace as well.

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The portals are membrane proteins

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which allow very specific materials and information

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to pass through the walls at the right times.

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Many interactions between robot proteins

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require some kind of push,

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think robot minimum wage.

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A few small but crucial forms of money

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are transferred between proteins

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to provide this push.

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Electrons, protons, oxygen, and phosphate groups

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are the main chemical currencies,

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and they're kept in small molecular wallets

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or larger tote bags to keep them safe.

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This is biochemistry,

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the study of how every part of the factory

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interacts to keep your life running smoothly

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in the face of extreme challenges.

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Maybe there's too much fuel;

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your body will store the excess as glycogen or fat.

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Maybe there's not enough;

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your body will use up those energy reserves.

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Maybe a virus or bacteria tries to invade;

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your body will mobilize the immune system.

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Maybe you touched something hot or sharp;

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your nerves will let you know so you can stop.

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Maybe it's time to create a new cell

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or a new person.

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Amazingly, oak trees, chickens, frogs,

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and, yes, even you

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share so many of the same

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basic robot and factory designs

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that biochemists can learn a lot

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about all of them

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all at the same time.