# investigating the water potential of potato cells

Lavender Nguyen’s Internal assignment

BIOLOGY SL

Internal assignment: Measure water potential of a potato’s cells

Research question: how is water potential of potato cells differ in different sucrose concentration?

Background information: Investigate the water potential of a potato’s cells in different sucrose concentrations. The concentrations will be: 0.8M, 0.4M, 0.2M, 0.15M, 0.075M and 0.00M.

Terminologies used in this experiment:

• Hypertonic solution: solution that has higher osmosis pressure (or has more solutes) than another solution to which it is compared.

• Hypotonic solution: a solution that contains less solute (more water) compared to the cytoplasm of the cell.

• Isotonic solution: Solutions of equal solute concentration

• Diffusion: the spread of particles through random motion from regions of higher concentration to regions of lower concentration.

• Osmosis: movement of solvent molecules through a selectively-permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves, without input of energy, across a semi-permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations

• Water potential: potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects such as surface tension. Water potential has proved especially useful in understanding water movement within plants, animals, and soil. Water potential is typically expressed in potential energy per unit volume and very often is represented by the Greek letter Ψ.

Hypothesis: in this experiment, 6 different concentrations of sucrose solution will be used to find the water potential of potato cells. They are 0.8M, 0.4M, 0.2M, 0.15M, 0.075M and 0.00M. Different concentration will have different affect on potato cells, hence, I will find out the water potential of a potato cells.

If the sucrose solution’s concentration is lower than the potato’s cells, the water molecules in the solution will move to the potato’s cells, so that the mass of potato tissues will increase. Vice versa, if the sucrose concentration is higher than the potato’s cells, the mass of potato tissues will decrease because the water molecules in the potato cells will move outside of the cells to the concentration and the particles in the solution will move to the potato’s cells. The movement of water molecules and sucrose solution’s particles is the result of a balance process between potato’s cells and ...