Hemoglobin vs. myoglobin: cooperative binding
Hemoglobin's oxygen-binding curve is sigmoidal, while myoglobin's is hyperbolic. What explains the difference?
Answer B: explanation for every choice
A
Myoglobin has the higher affinity: its P50 is about 3 mmHg, compared with about 26 mmHg for hemoglobin.
B
Correct. Hemoglobin shows positive cooperativity: binding shifts subunits from the low-affinity T state toward the high-affinity R state.
C
Each heme binds one O2. Hemoglobin carries four because it has four subunits.
D
Hemoglobin's Hill coefficient is about 2.8 to 3. Myoglobin's is 1.
TakeawaySigmoidal curve = cooperativity (Hill coefficient > 1). Single-subunit myoglobin is hyperbolic.
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Reviewed 2026-11-05 by a medical student. Spot an error? Report it with question ID bb6.