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Year 12 Science · Cell membranes and osmosis

Name: ______________________

Date: ____________

1. Which best defines osmosis?
- ☐ (a) Movement of any particle from low to high concentration
- ☐ (b) Net movement of water across a selectively permeable membrane towards higher solute concentration
- ☐ (c) Movement of glucose using ATP
- ☐ (d) Movement of salt across a membrane towards lower water concentration
2. A plant cell is placed in pure water. What happens?
- ☐ (a) It bursts
- ☐ (b) It becomes flaccid
- ☐ (c) It becomes turgid
- ☐ (d) Nothing happens
3. Which process requires energy from ATP?
- ☐ (a) Active transport
- ☐ (b) Diffusion
- ☐ (c) Osmosis
- ☐ (d) Evaporation
4. Red blood cells are placed in a strongly hypertonic salt solution. They will…
- ☐ (a) Swell and burst
- ☐ (b) Stay the same
- ☐ (c) Become turgid
- ☐ (d) Shrink as water leaves
5. Why must the potato strips be blotted before weighing?
- ☐ (a) To remove surface water that would add to the mass
- ☐ (b) To make them cooler
- ☐ (c) To stop osmosis
- ☐ (d) To add salt
6. A strip went from 4.0 g to 4.4 g. What is the percentage change in mass? (number, e.g. 5 or -5)
7. A strip went from 5.0 g to 4.5 g. What is the percentage change in mass? (number, e.g. 5 or -5)
8. What is the term for a plant cell membrane pulling away from the cell wall in a hypertonic solution?

Answer sheet

1. Net movement of water across a selectively permeable membrane towards higher solute concentration — Osmosis is specifically water moving towards the side with more dissolved solute.
2. It becomes turgid — Water enters, and the cell wall resists bursting, so the cell becomes turgid.
3. Active transport — Active transport moves substances against a gradient and requires ATP.
4. Shrink as water leaves — Water moves out towards the higher solute concentration, so cells shrink.
5. To remove surface water that would add to the mass — Surface liquid is not part of the cells and would distort the mass.
6. 10 — (4.4 − 4.0) ÷ 4.0 × 100 = 0.4 ÷ 4.0 × 100 = 10%.
7. -10 — (4.5 − 5.0) ÷ 5.0 × 100 = −0.5 ÷ 5.0 × 100 = −10%.
8. plasmolysis — Loss of water causes plasmolysis.