osmosis?

what is osmosis?

• the net movement of water molecules from a high water potential to a low water potential across a selectively/partially permeable membrane

how does water potential, thickness of membrane and surface area affect rate of osmosis?

• the lower the water potential, the slower the rate of osmosis

• the thicker the membrane, the slower the rate of osmosis

• the smaller the surface area, the slower the rate of osmosis

what plant is most commonly used to investigate the water potential of cells?

• potatoes

identifying the water potential of plant cells experiment?

• cut potato pieces into chips that are around 2cm long

  • the chips must all be the same shape, size, and mass

• weight each chip, then record the results

• put each chip into separate boiling tubes

• each boiling tube should contain different sucrose concentrations

  • use distilled water as the control group

• make sure the whole chip is submerged in the solution and heat in a water bath at 30C for 20 mins

• remove chips from solution, blot them dry, then weigh and remeasure the chips again

  • record this information in a table

• plot a graph. there should be both negative and positive values on the y-axis. draw a line of best fit

• the concentration where the line crosses the x-axis represents the water potential of the potato. this is the isotonic point

  • the isotonic point is where the water has not moved into or out of the tissue because the water potential is the same inside the cells as the solution is outside

how to find water potential of potato tissue?

• plot a graph with concentration on x axis and percentage change in mass on y axis

• find concentration where curve crosses the x-axis

• use another resource to find water potential of sucrose concentration

processed results meaning?

• calculations are made from a raw data table