AEMCA Practice Exam

How many binding sites does hemoglobin have?

1. 2 binding sites

2. 4 binding sites

3. 6 binding sites

4. 8 binding sites

The correct answer is: 4 binding sites

Hemoglobin has four binding sites for oxygen molecules. This quaternary structure consists of four polypeptide chains, each with an iron-containing heme group that can bind to one oxygen molecule. Therefore, hemoglobin can carry up to four oxygen molecules at a time, allowing for efficient oxygen transport throughout the body. This ability to bind multiple oxygen molecules is crucial for meeting the oxygen demands of various tissues during different physiological states. The other choices suggest fewer or greater binding sites, which do not accurately represent the well-established structure and function of hemoglobin. For instance, if hemoglobin had only two binding sites, it wouldn’t be as effective in fulfilling the oxygen transport needs in the body. Having six or eight binding sites would also not align with the known physiological properties of hemoglobin.