Each hemoglobin molecule can transport two molecules of oxygen.

FALSE. Each hemoglobin molecule can transport four molecules of oxygen.

Hemoglobin, or Hb, is a protein molecule found in red blood cells (erythrocytes) made of four subunits: two alpha subunits and two beta subunits. Heme the component of hemoglobin responsible for binding oxygen consists of an iron ion that binds oxygen and a porphyrin ring that binds the globin molecules, one molecule binds one molecule of oxygen and can bind up to four oxygen molecules.