Pyruvate Dehydrogenase Complex Tournament
Two onboarding diagrams orient you in pyruvate metabolism. Then eight MCAT-DoK quiz rounds: PDC's five cofactors, E1-E2-E3 mechanism, kinase/phosphatase regulation, thiamine deficiency in chronic alcoholism, and the classical lipoamide-poisoning of arsenite.
Where the Pyruvate metabolism fits in Aerobic respiration & pyruvate metabolism
The pyruvate dehydrogenase complex (PDC) is the irreversible bridge between glycolysis and the TCA cycle. It sits inside the mitochondrion and converts pyruvate + CoA + NAD+ into acetyl-CoA, NADH, and CO2. Click the highlighted Pyruvate metabolism box to enter the tournament.
Click the highlighted Pyruvate metabolism 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 the PDC step inside aerobic respiration on the live Reactome overview map.
Whole-Pathway Overview
Pan and zoom the curated WikiPathways TCA + PDC figure before you start answering.
Fill in the Blank
Recall PDC's net reaction: pyruvate + CoA + NAD+ -> acetyl-CoA + NADH + CO2.
Disruptor
Predict why thiamine-deficient alcoholics develop Wernicke encephalopathy + lactic acidosis.
Sequence Ordering
Order the four steps: E1 decarboxylation -> E2 transacetylation -> E3 reoxidation.
Match the Pairs
Pair E1/E2/E3 + PDK/PDP with their precise roles and cofactors.
Numeric Input
Count NADH produced by PDC per glucose (after glycolysis splits to 2 pyruvates).
Select All That Apply
Identify which signals (acetyl-CoA, NADH, ATP) inactivate PDC via PDK.
Odd One Out
Distinguish PDC's five cofactors from biotin (the carboxylase cofactor).
Arsenic Poisoning Disruptor
Predict how arsenite locks lipoamide and stalls PDC + αKGDH.
Public leaderboard
Your score posts to a global, persistent leaderboard scored by points first, time as tiebreaker.
PDC in 60 seconds
The pyruvate dehydrogenase complex sits in the mitochondrial matrix and links glycolysis to the TCA cycle. It carries out an irreversible oxidative decarboxylation: pyruvate + CoA + NAD+ -> acetyl-CoA + NADH + CO2. Because this step is irreversible, fatty-acid carbons (which converge on acetyl-CoA) cannot become net glucose.
PDC is built from three enzymes (E1, E2, E3) and uses five cofactors: TPP (B1), lipoate, CoA (B5), FAD (B2), and NAD+ (B3). Two homologous complexes - α-KG dehydrogenase and the branched-chain α-keto-acid dehydrogenase (MSUD enzyme) - share the same architecture, so a single B1 deficiency hits multiple metabolic nodes at once.
Regulation runs through PDK (phosphorylates / inactivates) and PDP (dephosphorylates / activates). PDK is activated by acetyl-CoA, NADH, and ATP (energy-replete signals). PDP is activated by Ca2+ (muscle contraction) and insulin (fed state). Pyruvate itself inhibits PDK - substrate-driven activation.
Two classic poisons hit PDC: chronic thiamine deficiency (alcoholism, malnutrition) -> Wernicke encephalopathy + lactic acidosis, and arsenite -> vicinal-thiol locking of lipoamide -> PDC + αKGDH both stall. Treatment: thiamine repletion (give B1 BEFORE glucose) or dimercaprol for arsenic.
FAQ
Why is PDC irreversible?
The decarboxylation step releases CO2 and the energy of the high-energy thioester (acetyl-CoA) is committed downstream. There is no PDC running in reverse, which is why fatty acids and ketones cannot make net glucose.
Why must thiamine be given before glucose in suspected Wernicke?
Glucose load demands TPP-dependent PDC + transketolase. In a thiamine-deplete patient, the glucose triggers further B1 consumption and can precipitate or worsen Wernicke encephalopathy. Always B1 first, then dextrose.
How is arsenite different from arsenate?
Arsenite (As III) covalently locks vicinal thiols (PDC and αKGDH lipoamide). Arsenate (As V) substitutes for phosphate in glycolysis (uncoupling substrate-level phosphorylation at GAPDH). Both are toxic but via distinct mechanisms.
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.