 Myoglobin can take the forms oxymyoglobin (MbO2), carboxymyoglobin (MbCO), and metmyoglobin (met-Mb), analogously to hemoglobin taking the forms oxyhemoglobin (HbO2), carboxyhemoglobin (HbCO), and methemoglobin (met-Hb).Like hemoglobin, myoglobin is a cytoplasmic protein that binds oxygen on a heme group.It harbors only one globulin group, whereas hemoglobin has four.