Final answer:
The name of the molecule formed when protoporphyrin within macrophages is broken down is unconjugated bilirubin. This is part of the normal breakdown of hemoglobin from aged red blood cells, with bilirubin eventually contributing to bile production and feces coloration.
Step-by-step explanation:
The molecule that is formed when protoporphyrin (from heme) within macrophages, which have consumed RBCs, is broken down, is called unconjugated bilirubin. Therefore, the correct answer to the question 'What is the name of the molecule shown in the figure?' out of the given options is option 4) Unconjugated bilirubin. This breakdown occurs as part of the degradation of hemoglobin, when red blood cells (RBCs) reach the end of their lifespan and are phagocytosed by macrophages primarily in the spleen, liver, and bone marrow.
The non-iron portion of heme is initially converted to biliverdin, which is a green pigment, and subsequently reduced to bilirubin, the yellow pigment. Bilirubin is then transported in the blood to the liver, where it is further processed and contributes to the manufacturing of bile. Eventually, in the large intestine, bilirubin is converted by bacteria to urobilinogen and then into stercobilin, which is excreted from the body in the feces, contributing to their brown color.