Water Potential · Paper 2 — Free Biology HL Practice Questions

A student investigates osmosis using cylinders of potato (Solanum tuberosum) tissue. She cuts five cylinders of equal size and mass, then places each in a different concentration of sucrose solution. After 30 minutes, she removes the cylinders, blots them dry, and measures their mass again. Her results are shown below. Sucrose concentration $(\text{mol dm}^{-3})$ — $0.0$ — $0.2$ — $0.4$ — $0.6$ — $0.8$ Percentage change in mass $(\%)$ — $+12$ — $+5$ — $-2$ — $-8$ — $-15$

A researcher studies water uptake in the freshwater plant Elodea canadensis. She places a leaf in a $10\%$ sucrose solution and observes the cells under a microscope. Initially, the chloroplasts are distributed throughout each cell. After 10 minutes, the chloroplasts are clumped in the centre of each cell, and the cell membrane has pulled away from the cell wall.