Enzyme Kinetics Tournament
Two onboarding diagrams put you inside carbohydrate metabolism. Then eight MCAT rounds: the definition of Km, a Lineweaver-Burk intercept, the E + S ⇌ ES → E + P sequence, parameter matching, hexokinase vs glucokinase curves, a half-Vmax calculation, Michaelis-Menten assumptions, and what a competitive inhibitor actually does to rate.
Where the Glucose metabolism (gluconeogenesis branch) fits in Metabolism of carbohydrates
Every carbohydrate pathway on this Reactome map is an enzyme-catalyzed rate problem. Hexokinase vs glucokinase, PFK-1 vs FBPase, and the bypasses of gluconeogenesis are the MCAT's favorite kinetic contrasts. Click the highlighted glucose-metabolism panel to enter the tournament.
Click the highlighted Glucose metabolism (gluconeogenesis branch) 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 8 test the high-yield mechanism, regulation, sequence and quantitative reasoning that consistently appear on test day.
The Bigger Picture
Anchor glucose-metabolizing enzymes on the live Reactome carbohydrate map.
Whole-Pathway Overview
Pan and zoom the WikiPathways glucose-metabolism figure before you answer.
Fill in the Blank
Recall that Km is [S] at one-half Vmax.
Disruptor
Read Km from a Lineweaver-Burk x-intercept.
Sequence Ordering
Order E + S ⇌ ES → E + P.
Match the Pairs
Pair Km, Vmax, k_cat, and both LB intercepts with their meaning.
Graph Reading
Read hexokinase vs glucokinase Michaelis-Menten curves.
Numeric Input
Compute v when [S] = Km.
Select All That Apply
Identify true Michaelis-Menten assumptions.
Odd One Out
Spot the change that lowers, not raises, unsaturated velocity.
Public leaderboard
Your score posts to a global, persistent leaderboard scored by points first, time as tiebreaker.
Enzyme kinetics in 60 seconds
Michaelis-Menten: v = Vmax [S] / (Km + [S]). Km is [S] at half Vmax — a low Km is high affinity. Vmax is the saturated rate and equals k_cat [E].
Lineweaver-Burk plots 1/v against 1/[S]. Y-intercept is 1/Vmax, x-intercept is -1/Km. The MCAT uses this plot to diagnose inhibitor type, which is the sister tournament.
Hexokinase (low Km, G6P-inhibited) traps glucose in every tissue at fasting concentrations. Glucokinase (high Km, liver and β-cell) only runs hard after a meal.
FAQ
Is Km the same as Kd?
Only when k_cat is negligible compared with k_off. In general Km = (k_off + k_cat) / k_on, so a very fast catalytic step inflates Km above the true dissociation constant.
Why does the MCAT love hexokinase vs glucokinase?
It is the cleanest tissue-specific kinetic pair on the exam. Same reaction (glucose → G6P), opposite physiologic jobs, opposite Km and regulation.
What is the Lineweaver-Burk x-intercept?
−1/Km. The y-intercept is 1/Vmax. The MCAT uses those two numbers to read affinity and capacity off a double-reciprocal plot without fitting a curve.
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.
Keep going
Overview diagram: Reactome Pathway R-HSA-71387, licensed CC BY 4.0. Reference figure: WikiPathways WP534.