WEBVTT 00:00:07.542 --> 00:00:09.632 Every chicken was once an egg, 00:00:09.632 --> 00:00:11.575 every oak tree an acorn, 00:00:11.575 --> 00:00:13.573 every frog a tadpole. 00:00:13.573 --> 00:00:15.283 The patch of mold on that old piece of bread 00:00:15.283 --> 00:00:16.735 in the back of your fridge, 00:00:16.735 --> 00:00:19.781 not so long ago that was one, solitary cell. 00:00:19.781 --> 00:00:21.569 Even you were once but a gleam 00:00:21.569 --> 00:00:23.742 in your parents' eyes. 00:00:24.818 --> 00:00:26.346 All these organisms share 00:00:26.346 --> 00:00:27.974 the same basic goal: 00:00:27.974 --> 00:00:30.633 to perpetuate their own existence. 00:00:31.448 --> 00:00:33.969 All lifeforms that we've discovered so far 00:00:33.969 --> 00:00:35.178 stay alive by using 00:00:35.178 --> 00:00:38.725 basically the same rules, materials, and machinery. 00:00:38.725 --> 00:00:41.940 Imagine a factory full of robots. 00:00:41.940 --> 00:00:43.028 These robots have two missions: 00:00:43.028 --> 00:00:44.572 one, keep the factory running, 00:00:44.572 --> 00:00:45.927 and two, when the time is right, 00:00:45.927 --> 00:00:48.484 set up an entirely new factory. 00:00:49.114 --> 00:00:49.783 To do those things, 00:00:49.783 --> 00:00:51.755 they need assembly instructions, 00:00:51.755 --> 00:00:52.862 raw materials, 00:00:52.862 --> 00:00:54.029 plenty of energy, 00:00:54.029 --> 00:00:56.003 a few rules about when to work normally, 00:00:56.003 --> 00:00:57.011 when to work quickly, 00:00:57.011 --> 00:00:58.037 or when to stop, 00:00:58.037 --> 00:00:59.627 and some exchange currencies 00:00:59.627 --> 00:01:02.587 because even robots need to get paid. 00:01:02.587 --> 00:01:05.292 Each factory has a high security office with blueprints 00:01:05.292 --> 00:01:08.260 for all the possible factory configurations 00:01:08.260 --> 00:01:09.641 and complete sets of instructions 00:01:09.641 --> 00:01:11.510 to make all the different types of robots 00:01:11.510 --> 00:01:13.793 a factory could ever need. 00:01:13.793 --> 00:01:15.971 Special robots photocopy these instructions 00:01:15.971 --> 00:01:16.843 and send them off 00:01:16.843 --> 00:01:19.469 to help make the building blocks of more robots. 00:01:19.469 --> 00:01:21.093 Their colleagues assemble those parts 00:01:21.093 --> 00:01:23.428 into still more robots, 00:01:23.428 --> 00:01:24.256 which are transported 00:01:24.256 --> 00:01:25.839 to the right location in the factory 00:01:25.839 --> 00:01:28.894 and given the tools they need to start working. 00:01:28.894 --> 00:01:30.261 Every robot draws energy 00:01:30.261 --> 00:01:32.148 from the central power plant, 00:01:32.148 --> 00:01:34.691 a giant furnace that can burn regular fuel 00:01:34.691 --> 00:01:36.057 but also scrap materials 00:01:36.057 --> 00:01:38.911 if not enough regular fuel is available. 00:01:39.895 --> 00:01:41.212 Certain zones in the factory 00:01:41.212 --> 00:01:42.794 have harsher working conditions, 00:01:42.794 --> 00:01:44.623 so these areas are walled off. 00:01:44.623 --> 00:01:46.875 But the robots inside can at least communicate 00:01:46.875 --> 00:01:48.045 with the rest of the factory 00:01:48.045 --> 00:01:49.454 through specialized portals 00:01:49.454 --> 00:01:51.464 embedded directly into the walls. 00:01:52.433 --> 00:01:53.723 And as you've probably figured out, 00:01:53.723 --> 00:01:55.141 what we're describing here 00:01:55.141 --> 00:01:56.429 is a cell. 00:01:56.429 --> 00:01:59.035 The high security office is the nucleus. 00:01:59.035 --> 00:02:00.392 It stores the blueprints and instructions 00:02:00.392 --> 00:02:03.515 as deoxyribonucleic acid, or DNA. 00:02:03.515 --> 00:02:06.226 The photocopied instructions are RNA. 00:02:06.226 --> 00:02:08.437 The robots themselves are mostly proteins 00:02:08.437 --> 00:02:09.852 built from amino acids, 00:02:09.852 --> 00:02:11.409 but they'll often use special tools 00:02:11.409 --> 00:02:13.227 that are, or are derived from, 00:02:13.227 --> 00:02:15.045 vitamins and minerals. 00:02:15.045 --> 00:02:16.863 The walls between factory zones 00:02:16.863 --> 00:02:18.333 and around the factory itself 00:02:18.333 --> 00:02:20.040 are mostly made up of lipids, 00:02:20.040 --> 00:02:22.084 a.k.a. fats. 00:02:22.084 --> 00:02:23.374 In most organisms, 00:02:23.374 --> 00:02:25.455 the primary fuel source are sugars, 00:02:25.455 --> 00:02:26.285 but in a pinch, 00:02:26.285 --> 00:02:27.954 fats and proteins can be broken down 00:02:27.954 --> 00:02:30.266 and burned in the furnace as well. 00:02:30.266 --> 00:02:32.349 The portals are membrane proteins 00:02:32.349 --> 00:02:34.847 which allow very specific materials and information 00:02:34.847 --> 00:02:37.789 to pass through the walls at the right times. 00:02:37.789 --> 00:02:39.555 Many interactions between robot proteins 00:02:39.555 --> 00:02:41.677 require some kind of push, 00:02:41.677 --> 00:02:43.923 think robot minimum wage. 00:02:43.923 --> 00:02:46.193 A few small but crucial forms of money 00:02:46.193 --> 00:02:47.983 are transferred between proteins 00:02:47.983 --> 00:02:49.811 to provide this push. 00:02:49.811 --> 00:02:52.939 Electrons, protons, oxygen, and phosphate groups 00:02:52.939 --> 00:02:54.486 are the main chemical currencies, 00:02:54.486 --> 00:02:56.612 and they're kept in small molecular wallets 00:02:56.612 --> 00:02:59.518 or larger tote bags to keep them safe. 00:02:59.979 --> 00:03:01.783 This is biochemistry, 00:03:01.783 --> 00:03:03.740 the study of how every part of the factory 00:03:03.740 --> 00:03:06.242 interacts to keep your life running smoothly 00:03:06.242 --> 00:03:08.822 in the face of extreme challenges. 00:03:08.822 --> 00:03:10.330 Maybe there's too much fuel; 00:03:10.330 --> 00:03:13.510 your body will store the excess as glycogen or fat. 00:03:13.510 --> 00:03:14.615 Maybe there's not enough; 00:03:14.615 --> 00:03:17.122 your body will use up those energy reserves. 00:03:17.122 --> 00:03:19.590 Maybe a virus or bacteria tries to invade; 00:03:19.590 --> 00:03:22.138 your body will mobilize the immune system. 00:03:22.138 --> 00:03:24.122 Maybe you touched something hot or sharp; 00:03:24.122 --> 00:03:26.967 your nerves will let you know so you can stop. 00:03:26.967 --> 00:03:29.687 Maybe it's time to create a new cell 00:03:29.687 --> 00:03:31.242 or a new person. 00:03:31.843 --> 00:03:34.569 Amazingly, oak trees, chickens, frogs, 00:03:34.569 --> 00:03:36.102 and, yes, even you 00:03:36.102 --> 00:03:37.646 share so many of the same 00:03:37.646 --> 00:03:39.894 basic robot and factory designs 00:03:39.894 --> 00:03:41.641 that biochemists can learn a lot 00:03:41.641 --> 00:03:42.911 about all of them 00:03:42.911 --> 00:03:45.202 all at the same time.