Advanced Placement (AP) Biology Practice Exam

The formula for solute potential is expressed as Ys = -iCRT. This equation is fundamental in understanding how solutes affect the movement of water across membranes through osmosis. In this formula: - Ys represents the solute potential, which is the tendency of water to move into a solution due to the presence of solute. - The negative sign indicates that the presence of solute lowers the water potential of the solution, as pure water (with no solute) has a solute potential of zero. - 'i' is the ionization constant, which represents the number of particles the solute dissociates into when dissolved. - 'C' is the molar concentration of the solute solution. - 'R' is the pressure constant, typically set at 0.0831 liter bar per mole per Kelvin. - 'T' is the temperature in Kelvin. By incorporating all these factors, this equation allows us to quantify the solute potential, reflecting how solute concentration influences the movement of water across membranes. This understanding is crucial in biological processes, such as cellular osmoregulation, where cells must maintain proper water balance relative to their internal solute concentrations.