Final answer:
Haptoglobin is the transport plasma protein that carries free hemoglobin from intravascular hemolysis to the macrophages of the mononuclear phagocyte system in the liver for further breakdown.
Step-by-step explanation:
The transport plasma protein that carries free hemoglobin from intravascular hemolysis to the macrophages of the mononuclear phagocyte system in the liver for further breakdown is haptoglobin. Haptoglobin binds to free hemoglobin released from damaged red blood cells and forms a complex that is then cleared by the liver. This prevents the free hemoglobin from causing damage to the kidneys and helps recycle the iron in hemoglobin for future use.