What If a Human Cell Were the Size of a City?

A protein inside you is sprinting at twice the speed of sound, dragging a building behind it. 🧬 Let's blow up a single human cell a billion times, to a city 20 km wide, and walk through it. Forget the calm blob with a yolk in the middle from your biology textbook. The real inside of a human cell is more crowded than a subway at rush hour. Its walls are liquid. Its power plants (mitochondria) hold back an electric field as strong as lightning. Its factories (ribosomes) build thousands of proteins every second. And its DNA is a cable that would reach the Moon and back five times, packed into one district. The strangest part? Almost nothing in there is steered. The whole city runs on collisions and chance, and it just works. Every number in this video is a real measurement. By the end you'll know how long the DNA inside you actually is (spoiler: it reaches Pluto). ⏱ Chapters 0:00 Intro: a supersonic courier inside you 0:27 The textbook cell is wrong 1:16 Scaling a cell up a billion times 2:13 The liquid wall (cell membrane) 3:00 Water gates: aquaporins 3:52 Cytoplasm: more packed than egg white 5:28 Highways: microtubules 6:05 Kinesin, the protein that walks 7:37 Mitochondria: power plants holding back lightning 9:22 ATP synthase, a real rotary motor 10:33 Ribosomes: the protein factories 12:00 The nucleus and its gates 13:13 DNA: a cable to the Moon and back 15:15 Where the city idea breaks: Brownian motion 17:21 A neuron one meter long 18:31 How many cells are you? 19:00 Your DNA reaches Pluto 20:14 Recap 📚 Sources • Ron Milo & Rob Phillips, Cell Biology by the Numbers, and the BioNumbers database • J. Ellis (2001), "Macromolecular crowding: obvious but underappreciated" • Svoboda et al. (1993), kinesin steps measured with optical tweezers • Noji, Yoshida et al. (1997), ATP synthase filmed rotating • Bianconi et al. (2013), Annals of Human Biology: cell count of the human body • Sender, Fuchs & Milo (2016): how many cells in the body have a nucleus • Molecular paintings by David Goodsell If this changed how you picture your own body, subscribe to The Brainery Lab. More "what if" science is on the way. #biology #humancell #science