CAIE IGCSE Biology 3.2 Osmosis Question Bank

Practise applying osmosis and water-potential gradients to animal cells, plant tissues and investigation data, including turgor, plasmolysis and percentage change.

Exam points

explain net water movement across a partially permeable membrane using a water-potential gradient
interpret plant-cell, red-blood-cell or tissue diagrams after immersion in contrasting solutions
use a percentage-change graph's zero-change point to infer that there is no net movement of water

Covered syllabus points

3.2.1—Water as a solvent 3.2.2—Water diffuses through partially 3.2.3—Osmosis through cell membranes 3.2.4—Osmosis using materials such 3.2.5—Effects on plant tissues of immersing 3.2.6—Plants are supported by the pressure 3.2.7—Osmosis as the net movement of water 3.2.8—Effects on plant cells of immersing 3.2.9—Importance of water potential

[Maximum number: 1]

Digestive enzymes catalyse the breakdown of large insoluble molecules.

State the name of the substance that is the solvent for most molecules that have been digested by enzymes.

[Maximum number: 9]

Some students investigated osmosis in raw potato sticks.

(a)

Define the term osmosis.

[ 3 ]

(b)

The students measured the mass of four of the potato sticks using an electronic balance.

Fig. 4.1 shows an electronic balance.

Fig. 4.1

The students left each potato stick in one of four different liquids for 5 hours:
- distilled water
- 0.1 mol per $\mathrm{dm}^{3}$ sodium chloride solution
- 0.5 mol per $\mathrm{dm}^{3}$ sodium chloride solution
- 1.0 mol per $\mathrm{dm}^{3}$ sodium chloride solution.

After 5 hours they measured the mass again and calculated the change in mass.

[ 1 ]

(i)

Predict which of the liquids would cause the largest decrease in mass of a potato stick.

[ 1 ]

1.0 (mol dm ${ }^{-3}$ sodium chloride solution) ;

(c)

After the experiment the students noticed that the potato stick with the lowest mass was soft and floppy.

Explain why the potato stick had become soft and floppy.

[ 3 ]

(d)

The students followed the same experimental procedure with boiled potato sticks and found no overall change in mass in any of the solutions.

Suggest why the mass of the boiled potato sticks remained the same.

[ 2 ]

[Maximum number: 1]

Fig. 5.1 is a diagram of a plant root hair cell.
Key
× nitrate ion
- water molecule

Fig. 5.1

State the name of the process that moves water molecules into root hair cells.

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Covered syllabus points

3.2 Osmosis question 1

3.2 Osmosis question 2

Question (a)

Question (b)

Question (i)

Question (c)

Question (d)

3.2 Osmosis question 3