IB DP Biology- D2.3 Water potential - IB Style Questions For SL Paper 1A -FA 2025
▶️ Answer/Explanation
The blood cells appear shriveled, indicating that water has moved out of the cells by osmosis.
This occurs when the surrounding solution has a higher solute concentration — a hypertonic environment — causing the cells to lose water and become crenated.
✅ Answer: (C) The solution is hypertonic as the cells are crenated.
This occurs when the surrounding solution has a higher solute concentration — a hypertonic environment — causing the cells to lose water and become crenated.
✅ Answer: (C) The solution is hypertonic as the cells are crenated.
▶️ Answer/Explanation
Correct answer: (C) They are passive transport mechanisms.
Both diffusion and osmosis involve movement of particles from an area of higher concentration to an area of lower concentration without the need for cellular energy, making them passive processes.
Diffusion is the movement of solute molecules, while osmosis refers specifically to the movement of water across a selectively permeable membrane.
Why other choices are incorrect:
A. Diffusion and osmosis occur in both living and non-living systems.
B. Transport proteins are needed for facilitated diffusion or active transport, not simple diffusion or osmosis.
D. Both processes move substances down the concentration gradient, not against it.
✅ Answer: (C)
▶️ Answer/Explanation
Correct answer: (B) I and II only
Osmosis is the passive movement of water across a selectively permeable membrane from higher water potential (lower solute concentration) to lower water potential (higher solute concentration).
Analysis of statements:
I. Correct – Water enters intestinal wall cells by osmosis because solute concentration is higher inside the cells than in the gut lumen.
II. Correct – In a hypertonic environment, water moves out of a plant cell by osmosis, leading to plasmolysis.
III. Incorrect – Evaporation is a physical change from liquid water to vapor; it does not involve membrane transport, so it is not osmosis.
✅ Answer: (B)
Osmosis is the passive movement of water across a selectively permeable membrane from higher water potential (lower solute concentration) to lower water potential (higher solute concentration).
Analysis of statements:
I. Correct – Water enters intestinal wall cells by osmosis because solute concentration is higher inside the cells than in the gut lumen.
II. Correct – In a hypertonic environment, water moves out of a plant cell by osmosis, leading to plasmolysis.
III. Incorrect – Evaporation is a physical change from liquid water to vapor; it does not involve membrane transport, so it is not osmosis.
✅ Answer: (B)