In which state can iron be transported by transferrin?

Transferrin, a glycoprotein found in the blood, has a specific role in the transport of iron throughout the body. It primarily binds to ferric iron (Fe+3) for transport. In this oxidized form, iron is stable and soluble, making it suitable for binding to transferrin, which effectively delivers iron to various tissues, including the liver, spleen, and bone marrow.

Ferric iron (Fe+3) is the correct form for transferrin because its binding at this oxidation state allows for efficient transport to cells that require iron for processes such as hemoglobin synthesis and cellular respiration. The other forms of iron, such as ferrous iron (Fe+2), are less stable when in the bloodstream and are typically converted to the ferric state before transport. Forms like Fe+4 are less common and not typically involved in biological transportation mechanisms, while Fe+0 represents elemental iron, which is not bound by transferrin. Therefore, ferric iron is the state that allows transferrin to perform its role effectively in iron transport.