Which molecule is responsible for transporting iron out of the gastrointestinal tract?

The molecule responsible for transporting iron out of the gastrointestinal tract is transferrin. Transferrin is a glycoprotein that binds iron in the bloodstream, facilitating its transport to various tissues where it is needed, such as the bone marrow for erythropoiesis.

In the gastrointestinal tract, when iron is absorbed primarily in its ferrous form (Fe2+) from dietary sources, it is then released into the circulation. Once in the blood, transferrin binds this iron and transports it to cells that require it, including the liver, spleen, and bone marrow. This mobilization is critical for maintaining iron homeostasis and ensuring that iron is available for vital processes like hemoglobin synthesis.

Other options listed serve different roles. Ferritin, for instance, is responsible for storing iron in a non-toxic form, while hemosiderin is an aggregate form of stored iron, typically found in tissues when iron overload occurs. Apotransferrin is the iron-free form of transferrin and does not transport iron until bound to it. Therefore, the key role of transporting iron out of the gastrointestinal tract and into the bloodstream distinctly belongs to transferrin.