Protein Folding & Denaturation Tournament
Two onboarding diagrams orient you in protein quality control. Then eight MCAT-level rounds: Anfinsen's principle, prion disease as conformational templating, the folding-to-proteasome life cycle, what each denaturant actually attacks, alpha helix geometry, the thermodynamics of the hydrophobic effect, which bonds hold which level of structure, and the unfolded protein response.
Where the Protein folding fits in Metabolism of proteins
Translation only produces a linear chain of amino acids - it is folding that turns that chain into a working molecule with a binding site, an active site, or a channel. On Reactome's protein metabolism map, the highlighted panel is exactly that step, sitting between synthesis of the polypeptide and everything a mature protein goes on to do. Click the highlighted Protein folding panel to enter the tournament.
Click the highlighted Protein folding box to continue.
What this tournament tests
Each task maps to a distinct MCAT cognitive demand. The first two orient you in the broader topology; the next eight test the high-yield mechanism, regulation, sequence and quantitative reasoning that consistently appear on test day.
The Bigger Picture
Anchor protein folding inside metabolism of proteins on the live Reactome map.
Whole-Pathway Overview
Pan and zoom the curated WikiPathways unfolded protein response figure before you start answering.
Fill in the Blank
Recall Anfinsen's principle - primary sequence carries all the information needed for the native fold.
Disruptor
Explain spongiform encephalopathy as PrPC being templated into beta-sheet-rich, protease-resistant PrPSc.
Sequence Ordering
Order the chain's life cycle: ribosomal release, Hsp70, hydrophobic collapse, chaperonin barrel, isomerases, native state, ubiquitination, proteasome.
Match the Pairs
Pair each agent (heat, pH, urea, SDS, beta-mercaptoethanol, Hsp70, chaperonin, ubiquitin ligase) with what it actually does.
Numeric Input
Recall the 3.6 residues per turn geometry of the right-handed alpha helix.
Select All That Apply
Identify TRUE statements about folding thermodynamics: solvent entropy, chain conformational entropy, the small negative net free energy change, and which bonds hold each level of structure.
Odd One Out
Separate peptide bonds (primary structure) from the side-chain interactions that maintain tertiary structure.
ER Stress Disruptor
Recognize the unfolded protein response - PERK, ATF6, IRE1, ERAD, and CHOP-driven apoptosis - in a secretory cell.
Public leaderboard
Your score posts to a global, persistent leaderboard scored by points first, time as tiebreaker.
Protein folding in 60 seconds
Anfinsen's principle: the primary sequence contains all the information needed to specify the native fold. Denatured ribonuclease A refolds spontaneously once urea and the reducing agent are removed. The dominant driving force is the hydrophobic effect - burying nonpolar side chains in the core releases the ordered water caged around them, so the entropy of the solvent increases. That gain, plus hydrogen bonds and van der Waals contacts, only slightly outweighs the conformational entropy the chain loses, so net ΔG of folding is small and negative and the native state is only marginally stable.
Know which bonds hold each level. Primary = peptide bonds. Secondary = backbone hydrogen bonds, giving the alpha helix (3.6 residues per turn, C=O of residue n to N-H of residue n+4) and beta sheets (hydrogen bonds between strands). Tertiary = side-chain interactions: hydrophobic packing, salt bridges, hydrogen bonds, and covalent disulfides. Quaternary = the same noncovalent forces assembling multiple subunits.
In a crowded cell, folding is a race against aggregation, so ATP-dependent chaperones intervene without adding information: Hsp70 shields exposed hydrophobic segments on the nascent chain, and the Hsp60 / GroEL chaperonin barrel lets one molecule fold in isolation. Two slow chemical steps get their own catalysts - protein disulfide isomerase shuffles cysteine pairs and prolyl isomerase converts X-proline bonds between cis and trans.
Denaturants sort cleanly by target: heat and pH extremes break noncovalent interactions, urea and guanidinium compete for hydrogen bonding, SDS coats the chain with negative charge, and only reducing agents such as beta-mercaptoethanol break disulfides - the peptide backbone survives all of them. Gentle denaturation is often reversible; boiling an egg is not. Failed folding is high yield clinically: amyloid is a beta-sheet-rich aggregate (Alzheimer disease), prions convert PrPC -> PrPSc by templating, and the unfolded protein response answers ER stress by slowing translation, inducing chaperones, and routing hopeless proteins to the ubiquitin-proteasome system before finally triggering apoptosis.
FAQ
If the sequence determines the fold, why does the cell need chaperones at all?
Chaperones change the kinetics, not the destination. A nascent chain emerges from the ribosome with hydrophobic patches exposed in a cytosol packed with other partly folded chains, so the fastest reaction is often aggregation with a neighbor rather than correct intramolecular collapse. Hsp70 and the Hsp60 chaperonin spend ATP to keep those patches shielded and to give the chain repeated chances to fold, which raises the yield of native protein without specifying its structure.
When is denaturation reversible and when is it not?
Reversibility depends on whether the unfolded chains stay soluble and separate. Mild, brief denaturation of a small single-domain protein is often fully reversible, as in Anfinsen's ribonuclease. Once unfolded chains find each other and form intermolecular aggregates, or once the exposed groups undergo chemical change, the process is effectively irreversible - which is why a boiled egg white never turns clear again even though no peptide bonds were broken.
How is amyloid different from ordinary protein aggregation?
Amyloid is a specific, highly ordered structure: cross-beta fibrils in which beta strands stack perpendicular to the fibril axis, giving a stable, protease-resistant, apple-green birefringent deposit on Congo red staining. Many unrelated proteins can adopt it - amyloid-beta in Alzheimer disease, transthyretin in familial and senile amyloidosis, immunoglobulin light chains in AL amyloidosis, and islet amyloid polypeptide in type 2 diabetes - which is why amyloid is described as a conformational rather than a sequence-specific disease.
What does SDS-PAGE tell me about protein structure?
SDS plus heat destroys secondary, tertiary, and quaternary structure and coats each chain with a roughly mass-proportional negative charge, so migration reflects mass alone rather than native charge or shape. Any subunits that still travel together are therefore held by disulfide bonds, and adding beta-mercaptoethanol resolves them - an IgG that runs as a single band unreduced separates into roughly 50 kDa heavy and 25 kDa light chains once reduced.
Do I need an account to play?
No. The tournament is fully public. You get a randomized handle and your score posts to the public leaderboard at the bottom of this page.
Keep going
How the polypeptide that has to fold gets built - ribosome, tRNA, and the initiation, elongation, and termination cycle.
What happens when proteins are taken apart - transamination, the nitrogen problem, and ketogenic versus glucogenic fates.
Overview diagram: Reactome Pathway R-HSA-392499, licensed CC BY 4.0.