BIOLOGY 5090 · STRUCTURED PRACTICE
An investigation was conducted to study osmosis in plant tissues and synthetic partially permeable membranes. In Part 1, a Visking tubing bag filled with 15 cm³ of 20% sucrose solution was attached to a glass capillary tube and submerged in a beaker of distilled water at 25 °C. The height of the liquid column in the capillary tube was recorded over 60 minutes. In Part 2, uniform potato cylinders of initial mass 5.00 g were placed into sucrose solutions of concentrations 0.0, 0.2, 0.4, 0.6, and 0.8 mol dm⁻³. After 60 minutes, the final mass of each potato cylinder was recorded.
Explain, in terms of water potential, why the liquid column in the capillary tube rose during Part 1.
The potato cylinder placed in 0.0 mol dm⁻³ sucrose solution (distilled water) increased in mass from 5.00 g to 5.65 g. Calculate the percentage change in mass of this potato cylinder. Show your working.
Describe the appearance of potato cells taken from the 0.8 mol dm⁻³ sucrose solution when viewed under a light microscope, and explain the biological cause of this appearance.
Total: 6 marks