Question

Why is oxygen haemoglobin dissociation curve sigmoid?

Answer 1

Hemoglobin's affinity for oxygenincreases as successive molecules ofoxygen bind. ... As this limit is approached, very little additionalbinding occurs and the curve levels out as the hemoglobin becomes saturated with oxygen. Hence thecurve has a sigmoidal or S-shape.

Answer 2

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$\purple\longmapsto\:$ Oxyhaemoglobin dissociation curve is obtained when percentage saturation of haemoglobin with O2 is plotted against the pO2.

$\purple\longmapsto\:$ At normal condition this curve is sigmoid and normal.

$\purple\longmapsto\:$ By increasing the concentration of CO2 ,the curve shifts towards right side.

$\purple\longmapsto\:$ By decreasing concentration Co2 the curve shifts towards left side.In this way the graph forms sigmoidal pattern.

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