You are interested in exocytosis and endocytosis in a line of cultured liver cells that secrete albumin and take up transferrin. To distinguish between these events, you tag transferrin with colloidal gold and prepare ferritin labeled antibodies that are specific for albumin. You add the tagged transferrin to the cell culture medium, and then after a few minutes you fix the cells, prepare thin sections, and react them with ferritin-labeled antibodies against albumin. Colloidal gold and ferritin are both electron-dense and therefore readily visible when viewed by electron microscopy. Additionally, they can be easily distinguished from one another on the basis of size. A) Will this experiment allow you to identify vesicles in the exocytic and endocytic pathways?
B) Not all the gold labeled vesicles are clathrin-coated. Explain this result.