Answer: Binding of one O2 increases affinity for subsequent O2 molecules.
- A The first O2 molecule binds with the highest overall affinity
- B Binding of one O2 increases affinity for subsequent O2 molecules
- C Each subunit binds O2 fully independently of the others
- D O2 binding affinity decreases with each subsequent molecule bound
Correct answer: B. Binding of one O2 increases affinity for subsequent O2 molecules
Explanation: Positive cooperativity: binding of the first O2 causes conformational change that increases affinity for subsequent O2. This gives the sigmoidal O2 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.