We look for some form of movement like walking, talking, breathing etc. or growth in the body part like height, size to confirm the organism is live. But this is not always true. For example, we can not detect a movement in plants and unicellular organism easily. So we look for molecular exchange. Molecules inside the cell move inside and outside in living cells. As a result, if there is a movement of molecules inside a cell, we can say that the organism is live.