Question

A small percentage of the body’s iron supply circulates freely in the blood, bound to a protein called transferrin. Transferrin binds to specific proteins on the surfaces of a cell's plasma membrane. The cell then ingests the transferrin by forming a pit, which becomes a vesicle. Which of the following BEST describes how transferrin is transported across the plasma membrane? A. exocytosis B. pinocytosis C. phagocytosis D. receptor-mediated endocytosis

Answer 1

What best describes how transferrin is transported through the erythrocyte plasma membrane is receptor-mediated endocytosis.

Step-by-step explanation:

The incorporation of transferrin across the erythrocyte membrane depends on a transferrin receptor expressed on the surface of the membrane. The specific receptor recognizes the presence of iron-charged transferrin, transferin diferrica, incorporating it into the cell by endocytosis. Once in the cytoplasm, the iron is dissociated from the transferrin.

Free transferrin is called apotransferrin. The transferrin receptor has a high affinity for transferrin di-ferrica, which facilitates its incorporation by endocytosis, and the release of apotransferrin into the extracellular space.

The other options are not correct because:

A. Exocytosis implies the exit of substances from the cell.

B. Pinocytosis involves the invagination of the membrane to incorporate soluble substances into the cell.

C. Phagocytosis is the incorporation of solid substances by invagination of the membrane.