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Hill Coefficient 2.8 — FRCA Primary MCQ

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HardPhysiology - RespiratoryHill Coefficient 2.8FRCA Primary

Regarding the oxyhaemoglobin dissociation curve which statement about the Hill coefficient is correct?

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Correct answer: D — The normal value is 2.8 reflecting cooperative binding

The Hill coefficient (n) for haemoglobin is approximately 2.8 (not 4 despite 4 binding sites). This reflects the degree of cooperativity in oxygen binding. n = 1 indicates no cooperativity (like myoglobin which has a hyperbolic dissociation curve). n > 1 indicates positive cooperativity giving the sigmoid shape. The higher the Hill coefficient the steeper the sigmoid curve.

Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist