Ketone Body Metabolism Tournament
Two onboarding diagrams orient you in lipid metabolism + ketogenesis. Then eight MCAT-DoK quiz rounds: HMG-CoA synthase as rate-limiting, β-OH-butyrate vs. acetoacetate, why liver makes but cannot use ketones, DKA biochemistry in T1DM, the energetic cost of thiophorase, and MCAD's paradoxical hypoketotic hypoglycemia.
Where the Ketone body metabolism fits in Metabolism of lipids
Ketone bodies are the liver's overflow product when fasting / starvation / DKA flood mitochondria with acetyl-CoA. They feed brain, heart, and skeletal muscle when glucose runs short. Click the highlighted Ketone body metabolism box to enter the tournament.
Click the highlighted Ketone body 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 ketogenesis inside lipid metabolism on the live Reactome overview map.
Whole-Pathway Overview
Pan and zoom the curated WikiPathways β-oxidation / ketogenesis figure before you start answering.
Fill in the Blank
Recall β-OH-butyrate (BHB) as the most abundant fasting plasma ketone.
Disruptor
Predict why insulin deficiency in T1DM cascades into severe DKA via lipolysis + low OAA.
Sequence Ordering
Trace 2 acetyl-CoA -> acetoacetyl-CoA -> HMG-CoA -> acetoacetate -> BHB.
Match the Pairs
Pair each enzyme (HMG-CoA synthase, lyase, BHB DH, thiophorase) with its precise role.
Numeric Input
Calculate ATP yield from full BHB oxidation (~21 ATP) using canonical TCA + ETC stoichiometry.
Select All That Apply
Identify TRUE facts: liver lacks thiophorase, RBCs cannot use ketones, DKA dipstick BHB blind spot.
Odd One Out
Distinguish acetyl-CoA (precursor) from the three actual ketone bodies.
MCAD Hypoketotic Hypoglycemia Fill-in
Recognize why FAO defects produce LOW ketones with hypoglycemia (no acetyl-CoA to drive ketogenesis).
Public leaderboard
Your score posts to a global, persistent leaderboard scored by points first, time as tiebreaker.
Ketones in 60 seconds
Ketones are the liver's response to prolonged fasting / DKA: high fatty-acid oxidation -> flood of acetyl-CoA -> oxaloacetate is drained for gluconeogenesis -> acetyl-CoA cannot enter the TCA -> HMG-CoA synthase shunts it into ketones.
Three molecules circulate: acetoacetate, β-hydroxybutyrate (most abundant), and acetone (volatile, fruity-breath byproduct). The BHB / acetoacetate ratio reports the mitochondrial NADH / NAD+ ratio.
The liver MAKES ketones but cannot USE them, because hepatocytes lack thiophorase (succinyl-CoA:acetoacetate CoA-transferase). Brain, heart, and muscle have thiophorase and consume ketones eagerly during fasting.
DKA pathology = no insulin -> uninhibited lipolysis -> massive ketone production + osmotic diuresis. Standard urine dipsticks miss BHB - so when the patient improves and BHB shifts back to acetoacetate, the dipstick can paradoxically look 'worse' even as plasma ketones fall.
FAQ
Why don't RBCs use ketones?
Red blood cells have NO mitochondria. They are obligate glucose-on-glycolysis cells with lactate as their endpoint. Even in deep starvation when ketones supply most other tissues, the brain reserves glucose for the RBCs and the renal medulla.
Why does the BHB-to-acetoacetate ratio matter clinically?
It reflects the mitochondrial NADH / NAD+ ratio. Severe shock or alcoholic ketoacidosis push BHB up disproportionately - which standard dipsticks miss. Always measure plasma BHB directly when the picture is severe.
Why is the brain's switch to ketones so important?
After ~3 days of fasting, ketones supply >50% of brain energy. This dramatically reduces the brain's glucose demand - protecting muscle from being broken down for gluconeogenic precursors. It is the metabolic basis of why we can fast for weeks without losing all lean mass.
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.