{"format":"molecular-machines.cards","version":1,"updated":"2026-10-12","decks":[{"machine":"groel","name":"GroEL–GroES","count":10,"url":"/learn/cards/groel.json"}],"cards":[{"id":"groel-what-it-does","machine":"groel","kind":"qa","prompt":"A new protein chain can get stuck half-folded, and its sticky patches can clump with other chains. What does GroEL do with such a chain?","answer":"It shuts the chain in a sealed chamber, where it folds alone.","explanation":"A lid protein, GroES, closes the chamber over one ring. Inside, the chain cannot meet other chains, so it cannot clump.","section":"summary","topic":"purpose","sources":["machine:summary","mechanism:Folding in isolation","stop:chain"],"tags":["folding","aggregation"],"difficulty":1,"url":"/machines/groel#summary","cites":[{"source":"machine:summary","machine":"groel","label":"Summary","section":"summary"},{"source":"mechanism:Folding in isolation","machine":"groel","label":"Step: Folding in isolation","section":"mechanism"},{"source":"stop:chain","machine":"groel","label":"Big picture: A new chain","section":"story"}]},{"id":"groel-fuel","machine":"groel","kind":"qa","prompt":"GroEL closes and opens its lid again and again, once per folding round. What fuel pays for each round?","answer":"ATP.","explanation":"One ring binds and splits seven ATP in each cycle. ATP synthase makes the ATP that GroEL spends.","section":"summary","topic":"purpose","sources":["machine:energy","stat:ATP per folding cycle","link:atp-synthase"],"tags":["energy","atp"],"difficulty":1,"url":"/machines/groel#summary","cites":[{"source":"machine:energy","machine":"groel","label":"Summary","section":"summary"},{"source":"stat:ATP per folding cycle","machine":"groel","label":"Key number: ATP per folding cycle","section":"summary"},{"source":"link:atp-synthase","machine":"groel","label":"Link to ATP synthase","section":"story"}]},{"id":"groel-capture-hydrophobic","machine":"groel","kind":"qa","prompt":"The rim of an open GroEL ring is water-repelling and sticky. A folded protein hides its own water-repelling parts. What lets the rim catch an unfolded protein?","answer":"The unfolded protein still shows water-repelling stretches, and the rim binds them.","explanation":"A folded protein buries these stretches inside, so the rim ignores it.","section":"mechanism","topic":"cycle","sources":["step:An unfolded protein is caught","mechanism:Capture"],"tags":["capture","hydrophobic"],"difficulty":1,"url":"/machines/groel#mechanism","cites":[{"source":"step:An unfolded protein is caught","machine":"groel","label":"Step: An unfolded protein is caught","section":"mechanism"},{"source":"mechanism:Capture","machine":"groel","label":"Step: Capture","section":"mechanism"}]},{"id":"groel-why-no-aggregation-inside","machine":"groel","kind":"qa","prompt":"Once the lid is on, the GroEL chamber has water-loving walls and room for just one protein. Why can the protein not clump in there?","answer":"It meets no other chains, so it has nothing to stick to.","explanation":"The walls are not sticky either, so the chain is free to fold.","section":"mechanism","topic":"cycle","sources":["mechanism:Folding in isolation","step:One ring is a closed chamber"],"tags":["folding","chamber"],"difficulty":1,"url":"/machines/groel#mechanism","cites":[{"source":"mechanism:Folding in isolation","machine":"groel","label":"Step: Folding in isolation","section":"mechanism"},{"source":"step:One ring is a closed chamber","machine":"groel","label":"Step: One ring is a closed chamber","section":"mechanism"}]},{"id":"groel-hydrolysis-timer","machine":"groel","kind":"qa","prompt":"With the lid on, GroEL splits its ATP slowly. After the split, the ring holds the lid less tightly. So what does the time to split ATP control?","answer":"How long the chamber stays shut.","explanation":"The ATP split works as a timer that gives the protein time to fold before the lid can come off.","section":"mechanism","topic":"cycle","sources":["step:ATP is split: the timer","mechanism:Hydrolysis primes release"],"tags":["atp","timer"],"difficulty":2,"url":"/machines/groel#mechanism","cites":[{"source":"step:ATP is split: the timer","machine":"groel","label":"Step: ATP is split: the timer","section":"mechanism"},{"source":"mechanism:Hydrolysis primes release","machine":"groel","label":"Step: Hydrolysis primes release","section":"mechanism"}]},{"id":"groel-what-opens-old-chamber","machine":"groel","kind":"qa","prompt":"GroEL has two rings that take turns, so only one chamber folds a protein at a time. What makes the closed chamber on one ring open again?","answer":"ATP and a new protein binding the other ring.","explanation":"That binding throws off the lid and the protein from the first ring. The protein leaves whether it has folded or not.","section":"mechanism","topic":"cycle","sources":["mechanism:The other ring fires","step:The old chamber opens"],"tags":["rings","alternation"],"difficulty":2,"url":"/machines/groel#mechanism","cites":[{"source":"mechanism:The other ring fires","machine":"groel","label":"Step: The other ring fires","section":"mechanism"},{"source":"step:The old chamber opens","machine":"groel","label":"Step: The old chamber opens","section":"mechanism"}]},{"id":"groel-sr1-folds-inside","machine":"groel","kind":"qa","prompt":"Scientists built a GroEL with a single ring that closes its lid but never opens again. A protein trapped inside still became active. What does this show?","answer":"The protein folds inside the closed chamber, not only after it leaves.","explanation":"It is open how much the chamber actively helps the fold, beyond keeping other chains away. Some proteins fold faster in a slightly smaller chamber.","section":"evidence","topic":"debate","sources":["evidence:folding-inside-single-ring","frontier:Single-ring reactors","analogy:A quiet room for one","step:The protein folds inside"],"tags":["chamber","folding"],"difficulty":2,"url":"/machines/groel#evidence","cites":[{"source":"evidence:folding-inside-single-ring","machine":"groel","label":"Folding inside a cage that never opens (Weissman JS 1996)","section":"evidence","anchor":"ev-folding-inside-single-ring"},{"source":"frontier:Single-ring reactors","machine":"groel","label":"Open question: Single-ring reactors","section":"summary"},{"source":"analogy:A quiet room for one","machine":"groel","label":"Analogy: A quiet room for one","section":"story"},{"source":"step:The protein folds inside","machine":"groel","label":"Step: The protein folds inside","section":"mechanism"}]},{"id":"groel-share-of-proteins","machine":"groel","kind":"qa","prompt":"GroEL is a busy helper in a growing E. coli cell, and it gets busier under heat stress. Roughly what share of the cell's cytoplasmic proteins pass through it in normal growth?","answer":"About one in ten.","explanation":"Measured in living cells as 10 to 15 percent, and 30 percent or more under heat stress.","section":"story","topic":"numbers","sources":["fact:G4","story:summary"],"tags":["scale"],"difficulty":1,"url":"/machines/groel#story","cites":[{"source":"fact:G4","machine":"groel","label":"Share of cytoplasmic protein that passes through GroEL: 10–15 %","section":"story"},{"source":"story:summary","machine":"groel","label":"Big picture","section":"story"}]},{"id":"groel-essential-for-growth","machine":"groel","kind":"qa","prompt":"Most E. coli proteins fold without help, but a small group of hard cases need GroEL. What happens to E. coli that has no GroEL?","answer":"It cannot grow at all.","explanation":"About 85 proteins need GroEL to fold, and some of those are essential for life.","section":"story","topic":"purpose","sources":["fact:G8","fact:G7","story:summary"],"tags":["essential"],"difficulty":1,"url":"/machines/groel#story","cites":[{"source":"fact:G8","machine":"groel","label":"Temperatures at which E. coli needs GroEL and GroES to grow: 17–42 °C","section":"story"},{"source":"fact:G7","machine":"groel","label":"E. coli proteins that bind GroEL: 250 of about 2,400 cytosolic proteins","section":"story"},{"source":"story:summary","machine":"groel","label":"Big picture","section":"story"}]},{"id":"groel-proteasome-chamber","machine":"groel","kind":"qa","prompt":"GroEL and the proteasome are both closed chambers that hold one protein. What is the difference in what happens to the protein inside each?","answer":"In GroEL it gets a place to fold; in the proteasome it gets destroyed.","explanation":"In your cells, many new proteins that fold wrong go to the proteasome.","section":"story","topic":"purpose","sources":["link:proteasome","machine:summary"],"tags":["links","proteasome"],"difficulty":2,"url":"/machines/groel#story","cites":[{"source":"link:proteasome","machine":"groel","label":"Link to Proteasome","section":"story"},{"source":"machine:summary","machine":"groel","label":"Summary","section":"summary"}]}]}