When the Oxygen-Saturation Curve of Hemoglobin Is Analyzed by Use

Multiple Choice

When the oxygen-saturation curve of hemoglobin is analyzed by use of the Hill equation, a Hill constant of about 3 is found. This means that

A) only 3 of the 4 hemes can bind O2.
B) negative cooperativity causes hemoglobin to behave as if it had only 3 hemes that can bind O2.
C) each of the 4 hemes can bond O2, but not as tightly as they would in the absence of cooperativity.
D) the binding of O₂ is highly, but not perfectly, cooperative.
E) 3 of the heme groups bind O₂ equally tightly, and the 4th heme binds O₂ more tightly.