Answer:
Due to their sizes.
Step-by-step explanation:
Some materials diffuse through a semipermeable membrane because of their small size which can pass through small pores present in the semipermeable membrane of the cell while on the other hand, some molecules can't diffuse through semipermeable membrane of the cell due to its large size. Glucose, oxygen and sodium are the examples which are smaller in size and can diffuse through semipermeable membrane whereas fats, carbohydrates and proteins are big in size so it can diffuse through semipermeable membrane of the cell.