If all human hemoglobin were free in the plasma rather than being contained in RBCs, the circulatory fluid would be too viscous for the cardiovascular system to function effectively.
Ademais, se toda a hemoglobina humana estivese flotando libre no plasma (en lugar de estar toda dentro dos glóbulos vermellos), o fluído circulatorio sería demasiado viscoso para que o sistema cardiovascular puidese funcionar eficazmente.