Which Statement About Positive Cooperativity of Hemoglobin Is True

Multiple Choice

Which statement about positive cooperativity of hemoglobin is true?

A) Binding by the first O₂ molecule means that a larger increase in PO₂ is needed for hemoglobin to bind a second O₂ molecule.
B) Positive cooperativity results from changes in the primary structure of hemoglobin.
C) Positive cooperativity applies for binding the fourth O₂ molecule once a third O₂ molecule is bound.
D) The linear relationship between PO₂ and the amount of O₂ bound to hemoglobin reflects positive cooperativity.
E) Binding by the second O₂ molecule allows the third O₂ molecule to bind more easily.