In cellular systems, water can move easily across membranes, but other molecules __ Therefore, it is often only water that can move and follow the law of diffusion. According to the law of diffusion, water will move from where it is more concentrated (less __ ) to an area of lower water concentration. The amount of solute per unit volume is referred to as __ With respect to cell systems ISOTONIC: HYPOTONIC: HYPERTONIC:

In cellular systems, water can move easily across membranes, but other molecules **cannot**. Therefore, it is often only water that can move and follow the law of diffusion.<br /><br />According to the law of diffusion, water will move from where it is more concentrated (less **solute**) to an area of lower water concentration.<br /><br />The amount of solute per unit volume is referred to as **concentration** or **osmolarity**.<br /><br />With respect to cell systems:<br /><br />* **ISOTONIC:** Two solutions are isotonic when they have the same concentration of solute. There is no net movement of water across the membrane.<br /><br />* **HYPOTONIC:** A hypotonic solution has a lower concentration of solute compared to another solution. Water will move *into* a cell placed in a hypotonic solution.<br /><br />* **HYPERTONIC:** A hypertonic solution has a higher concentration of solute compared to another solution. Water will move *out of* a cell placed in a hypertonic solution.<br />