The tiny structures inside of cells, such as Ribosomes or chloroplasts that have specialized roles are called organelles. These structures are found in the cytoplasm of eukaryotic cells and are enclosed with a membrane. These tiny structures are not present in prokaryotes like in bacteria.
When the fish is put into fresh water, suddenly the concentration around them is very low and the water potential is extremely high. Water will now move from the relatively high water potential in the water to the relatively low water potential in the cells, the cells start to burst and the fish dies.
Answer:
it allows only some materials to pass through and leave the cell.
Neuroglial Cells is the answer