Question

The oxygen-hemoglobin dissociation curve is sigmoid because

Answer 1

When the concentration in terms po2 of o2 is more then there is no need of 02 in tissues as in alveoli but as the pc02 increases and also the po2 decrease , (increase in ph may also effect). The o2molecules dissociate

from haemoglobin and thus the curve bends right and makes a sigmoid. Note binding efficiency if co2 with haemoglobin is more than o2.