What is the total molecular mass of hemoglobin?

Hemoglobin is a complex protein found in red blood cells, primarily responsible for the transportation of oxygen throughout the body. The molecular mass of hemoglobin is typically around 64,500 daltons (or grams per mole), which is commonly rounded to approximately 64 to 65 kDa (kilodaltons). This mass corresponds well with the answer provided and is consistent with the commonly accepted values in biochemistry.

Understanding the molecular structure of hemoglobin can help clarify why its mass falls into this range. It is composed of four subunits, each containing a heme group that binds oxygen. This quaternary structure contributes to its overall molecular weight. The other values presented in the choices are either too low or way too high for a protein of this nature, as proteins typically range in mass from a few thousand to several hundred thousand daltons, but rarely reach the extreme numbers suggested in the higher range. Hence, the choice of 65 k g/mol aligns with established biochemical knowledge of hemoglobin's molecular weight.