How does positive cooperativity contribute to the sigmoidal shape of hemoglobin's oxygen binding curve?

• A. It has no effect on the shape of the oxygen binding curve.
• B. It causes hemoglobin to bind oxygen less efficiently, resulting in a hyperbolic curve.
• C. It allows hemoglobin to bind oxygen more efficiently after the first molecule is bound, creating an S-shaped curve.
• D. It prevents hemoglobin from binding oxygen, resulting in a linear curve.

Answer: (C)