Blood Components Tournament
Two onboarding diagrams orient you in the red cell's gas-transport machinery. Then eight MCAT-DoK quiz rounds: why an anucleate red cell can only run glycolysis, carbon monoxide poisoning with a normal PaO2, the full CO2-pickup choreography, blood components and erythrocyte proteins, hemoglobin's P50, the CADET-right-shift rules, myoglobin vs. hemoglobin cooperativity, and why one substituted amino acid causes vaso-occlusive crises.
Where the Erythrocytes take up carbon dioxide and release oxygen fits in O2/CO2 exchange in erythrocytes
Reactome splits erythrocyte gas exchange into the two halves of the same round trip: the lung-side panel, where the red cell loads O2 and dumps CO2, and the tissue-side panel below it, where everything runs in reverse. The highlighted tissue-side panel is where the Bohr effect, the Haldane effect, carbonic anhydrase, and the chloride shift all live. Click the highlighted Erythrocytes take up carbon dioxide and release oxygen panel to enter the tournament.
Click the highlighted Erythrocytes take up carbon dioxide and release oxygen 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 tissue-side gas exchange inside erythrocyte O2/CO2 transport on the live Reactome map.
Whole-Pathway Overview
Pan and zoom the curated WikiPathways erythropoiesis figure before you start answering.
Fill in the Blank
Recall why a mitochondria-free erythrocyte can make ATP only by anaerobic glycolysis.
Disruptor
Explain carbon monoxide poisoning - severe hypoxia with a normal PaO2 and a falsely reassuring pulse oximeter.
Sequence Ordering
Trace CO2 entry -> carbonic anhydrase -> bicarbonate and H+ -> Bohr unloading -> Haldane loading -> chloride shift -> lung reversal.
Match the Pairs
Pair each blood component and red cell protein (band 3, carbonic anhydrase, 2,3-BPG, EPO, neutrophil, eosinophil) with its role.
Numeric Input
Recall the P50 of adult hemoglobin, the reference point for every curve shift.
Select All That Apply
Identify which factors right-shift the dissociation curve - CO2, acid, 2,3-BPG, exercise, temperature.
Odd One Out
Separate monomeric, hyperbolic myoglobin from cooperative, sigmoidal hemoglobin.
Sickle Cell Disruptor
Connect the beta-6 glutamate-to-valine substitution to deoxygenation-dependent polymerization and crisis triggers.
Public leaderboard
Your score posts to a global, persistent leaderboard scored by points first, time as tiebreaker.
Blood and gas transport in 60 seconds
Whole blood is roughly 55 percent plasma and 45 percent formed elements, and the hematocrit is essentially the erythrocyte fraction. Mature red cells eject the nucleus and mitochondria, so they run anaerobic glycolysis only (never consuming their own cargo) and shunt about a tenth of their glucose into the pentose phosphate pathway for NADPH - the reason G6PD deficiency hemolyzes under oxidative stress. Erythropoietin from the kidney drives production, so chronic kidney disease causes a normocytic anemia.
Hemoglobin is a tetramer (two alpha, two beta), and its four subunits cooperate: binding at one heme shifts the protein from the T state toward the R state, producing the sigmoidal curve. Monomeric myoglobin has no partners, so its curve is hyperbolic and it holds O2 until PO2 is very low - a storage protein, not a transporter. The reference point is P50, about 26 to 27 mmHg.
Right shifters spell CADET - CO2, Acid, 2,3-DPG, Exercise, Temperature - all signatures of a tissue that needs O2 now; the Bohr effect is the acid-driven piece. The mirror-image Haldane effect says deoxygenated hemoglobin binds CO2 and H+ better. CO2 rides home about 70 percent as plasma bicarbonate (made by carbonic anhydrase, exported by band 3 in exchange for Cl-), about 20 to 23 percent as carbaminohemoglobin, and under 10 percent dissolved.
High-yield pathology: carbon monoxide lowers carrying capacity and left-shifts the rest, giving tissue hypoxia with a normal PaO2 and a normal-looking pulse oximeter; methemoglobinemia (Fe3+) gives chocolate-brown blood treated with methylene blue. Sickle cell disease is a structural defect (beta-6 Glu to Val) where only deoxygenated HbS polymerizes, while the thalassemias are quantitative defects in chain synthesis and hereditary spherocytosis is a membrane cytoskeleton defect.
FAQ
Why can pulse oximetry read 99 percent in a patient who is severely hypoxic?
Standard two-wavelength pulse oximetry cannot distinguish carboxyhemoglobin from oxyhemoglobin, so carbon monoxide poisoning reads falsely high. PaO2 is also normal, because it measures only dissolved O2 - and CO does not displace dissolved gas. What has fallen is O2 CONTENT, which depends on how many heme sites are actually available. Co-oximetry, or simply the exposure history, makes the diagnosis, and treatment is high-flow or hyperbaric oxygen.
What is the difference between the Bohr and Haldane effects?
They are two faces of the same allosteric coupling. Bohr describes O2 release: rising CO2 and H+ in a working tissue lower hemoglobin's O2 affinity, so more O2 is unloaded. Haldane describes CO2 pickup: once hemoglobin gives up O2, it binds CO2 and protons more readily. Together they make the red cell self-regulating - the tissues that produce the most acid and CO2 automatically extract the most oxygen.
Why does fetal hemoglobin bind oxygen more tightly than adult hemoglobin?
Fetal hemoglobin is two alpha and two gamma chains, and the gamma chains bind 2,3-BPG poorly. Because 2,3-BPG is what normally stabilizes the low-affinity deoxy state, its weaker binding leaves HbF left-shifted with a P50 near 19 to 20 mmHg. That gradient is what lets the fetus strip O2 from maternal blood across the placenta. It is also why hydroxyurea helps in sickle cell disease: HbF does not join the HbS polymer.
Why does 2,3-BPG rise at altitude?
Chronic hypoxia increases red cell glycolytic flux through the Rapoport-Luebering shunt, raising 2,3-BPG over a few days. 2,3-BPG binds the central cavity between the beta chains of deoxyhemoglobin, stabilizing the T state and right-shifting the curve so more O2 is released per pass. Combined with hyperventilation (immediate) and erythropoietin-driven polycythemia (weeks), it is one of the three classic altitude adaptations.
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
Where the heme inside every hemoglobin comes from - ALA synthase, the porphyrias, and lead poisoning.
What the platelets and plasma factors in this same blood do when a vessel is breached.
Overview diagram: Reactome Pathway R-HSA-1480926, licensed CC BY 4.0.