The model below represents a beaker filled with water and glucose (diamond symbols). The beaker is separated in half by a semi-permeable barrier consisting of a cell membrane and all of its protein components.

[Beaker concentrated more on left than right]

If the membrane in the beaker were only permeable to the water, the water would move due to _______.

The water in the beaker moves from the side with higher water concentration to the side with lower concentration (higher glucose concentration) due to osmosis until equilibrium is reached.

Explanation:

The water in the beaker would move from the side with a higher concentration of water (lower glucose concentration) to the side with a lower concentration of water (higher glucose concentration) due to osmosis. Osmosis is the diffusion of water through a semipermeable membrane from a region of higher water concentration to one of lower water concentration, attempting to equalize concentrations on both sides of the membrane. In the described beaker, where the membrane is permeable to water but not to glucose, the selective permeability allows only water to move. The water will continue to flow to the side with the higher concentration of glucose until the osmotic pressure caused by the difference in solute concentration is balanced by the hydrostatic pressure that builds up due to the increased water level, or until the concentration gradient disappears and equilibrium is achieved.

The process is driven by the tendency of the system to reach thermodynamic equilibrium. The hypertonic solution on one side, being more concentrated with glucose and having less water, causes water from the hypotonic side, which has a higher water concentration, to cross the membrane. Upon crossing the membrane, the water equalizes the solute concentrations, thereby establishing isotonic conditions. Once this equilibrium is reached, there will be no net movement of water across the membrane; however, individual water molecules may still move back and forth.