Final answer:
When oxygen binds to heme, hemoglobin assumes a slightly different shape and is called oxyhemoglobin (HbO₂). This change increases hemoglobin's affinity for oxygen, shown by the sigmoidal O₂-binding curve, demonstrating cooperative binding where each subsequent oxygen binds more easily until the hemoglobin is nearly saturated.
Step-by-step explanation:
When oxygen binds to heme, hemoglobin changes shape and is known as oxyhemoglobin.
This conformational change facilitates the binding of additional oxygen molecules, characteristic of the cooperative binding nature of hemoglobin.
The S-shaped or sigmoidal O₂-binding curve of hemoglobin demonstrates how the affinity for oxygen increases after the initial molecules bind, making it easier to bind a second and third oxygen molecule.
However, binding the fourth oxygen molecule is more difficult. This effect is due to the physical changes in the spatial structure of the hemoglobin protein as O₂ molecules bind.
Oxygen binding alters the conformation of hemoglobin, increasing its oxygen affinity until it becomes nearly saturated. The oxygen dissociation curve of hemoglobin is sigmoidal due to the cooperative nature of this binding.
The transformation from hemoglobin without bound oxygen, called deoxyhemoglobin, to hemoglobin with bound oxygen, known as oxyhemoglobin, is essential for the efficient transport and release of oxygen by red blood cells.