Final answer:
Cooperative binding exhibits an S-shaped curve in cases of positive cooperativity, like that seen in hemoglobin's oxygen-binding curve. Negative cooperativity would show a curve with a steeper slope and quick leveling off, which can be advantageous when proteins need to be saturated at lower ligand concentrations.
Step-by-step explanation:
Cooperative binding in biology typically refers to the situation where the binding of a ligand to a protein enhances the affinity of additional ligand molecules. In cases of positive cooperativity, as the ligand concentration increases, each additional ligand molecule that binds to the protein increases the protein's affinity for the next ligand. This results in a characteristic S-shaped or sigmoidal curve when the percentage of binding sites occupied (Y-axis) is plotted against the ligand concentration ([L], X-axis). This is well exemplified by the oxygen-binding curve of hemoglobin, which shows that the affinity of oxygen for heme increases as more oxygen molecules bind.
Negative cooperativity, on the other hand, occurs when ligand binding decreases the affinity for subsequent ligand molecules. This is usually represented by a curve with a steeper initial slope that levels off more quickly than the S-shaped positive cooperativity curve. A low value of K (indicating the ligand concentration at which the binding site on a protein is half occupied) with negative cooperativity might be advantageous in conditions where it is beneficial for a protein to become saturated with ligand molecules at lower concentrations, thus ensuring efficient function even at low ligand availabilities.