The part of the curve in shaded area a has a steeper slope than the part of the curve in area b. true each shaded area on the x axis represents a 5 mm hg range in partial pressure of oxygen. true each shaded area on the y axis represents a 10% range in o2 saturation of hemoglobin. false if the partial pressure of oxygen in the blood dropped from 25 to 20 mm hg, the percent o2 saturation of hemoglobin would decrease to about 25%.