What is the correct order of steps from iron absorption to incorporation into heme?

The correct order of steps from iron absorption to incorporation into heme is indeed represented by the choice provided.

First, dietary iron is absorbed in the intestines. This initial absorption occurs primarily in the duodenum, where iron can be in either the ferric (Fe3+) or ferrous (Fe2+) state. Ferrous is the more absorbable form.

Next, once inside the intestinal cells, iron can either be stored as ferritin or transported into circulation via a specific transporter protein. This transport happens in the next step, allowing iron to enter the bloodstream where it can bind to transferrin, the protein responsible for transporting iron in the plasma.

After entering the circulation via transferrin, iron is delivered to the bone marrow, the site of erythropoiesis (the formation of new red blood cells). Here in the bone marrow, iron is then incorporated into hemoglobin, which contains the heme group.

Lastly, the heme is synthesized by combining iron with protoporphyrin IX inside the mitochondria of erythroid precursor cells, completing the pathway from iron absorption to incorporation into heme.

This sequential process underlines the critical steps of iron metabolism and highlights the various roles of proteins for transport and incorporation