Myoglobin vs Hemoglobin
Start with the big picture
Myoglobin is a 153-amino-acid monomer with one heme, while adult hemoglobin (HbA) is an α₂β₂ tetramer with four hemes. Their oxygen-binding curves reflect this structural difference: myoglobin binds oxygen hyperbolically without cooperativity, whereas hemoglobin binds it sigmoidally through positive cooperativity between subunits. Myoglobin has higher oxygen affinity; hemoglobin’s affinity changes with factors including pH, CO₂, 2,3-BPG, and temperature. Hemoglobin’s T and R conformations help explain this allosteric regulation and the Bohr effect. Their distinct roles also inform clinical interpretation: hemoglobin variants are associated with disorders such as sickle cell disease and thalassemias, while increased serum myoglobin can indicate acute muscle injury.
What you'll learn
- Compare the subunit structure and heme content of myoglobin and HbA.
- Distinguish their oxygen-binding curves and explain the role of cooperativity.
- Describe hemoglobin’s allosteric regulation, T–R states, and Bohr effect.
- Relate each protein’s function to the clinical findings noted in the source.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
