Complex sentence: There are two transferrin receptors in humans, transferrin receptor 1 and transferrin receptor 2.Cellular iron uptake occurs chiefly via these two well documented transferrin receptors, the existence of a receptor for transferrin iron uptake being recognized over half a century back.
Split into simpler sentences: There are two transferrin receptors in humans, transferrin receptor 1 and transferrin receptor 2.Cellular iron uptake occurs chiefly via these two well documented transferrin receptors. The existence of a receptor for transferrin iron uptake being recognized over half a century back.