Answer: Binding of one O 2 increases affinity for subsequent O 2 molecules.
- A The first O<sub>2</sub> molecule binds with the highest overall affinity
- B Binding of one O<sub>2</sub> increases affinity for subsequent O<sub>2</sub> molecules
- C Each subunit binds O<sub>2</sub> fully independently of the others
- D O<sub>2</sub> binding affinity decreases with each subsequent molecule bound
Correct answer: B. Binding of one O<sub>2</sub> increases affinity for subsequent O<sub>2</sub> molecules
Explanation: Positive cooperativity: binding of the first O<sub>2</sub> causes conformational change that increases affinity for subsequent O<sub>2</sub>. This gives the sigmoidal O<sub>2</sub> dissociation curve of hemoglobin.
As substrate concentration rises, reaction rate increases steeply at first, then plateaus at Vmax once every enzyme molecule is working at full capacity; Km is the substrate concentration giving half-maximal rate, and a LOWER Km means the enzyme reaches that rate with less substrate (higher affinity).
Concept context
Carbohydrates, proteins, lipids, nucleic acids, and enzyme kinetics. Essential foundation for understanding metabolism.