The plasma glycoprotein Tf binds up to 2 ferric (Fe³⁺) ions per molecule. Iron-bound forms of Tf bind to the Tf receptor (TfR) to deliver iron to cells. Tf is a bilobed protein that contains an iron binding site within each lobe. Thus, the monoferric forms of Tf carry iron in either their amino-terminal (N) lobe or carboxy-terminal (C) lobe.