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IB Biology SL D2.3 Water Potential Question Bank

Practise IB Biology SL D2.3 by explaining osmosis and predicting plant and animal cell responses in water-potential experiments.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • explain osmosis across a partially permeable membrane using solute concentration differences
  • deduce cell changes such as plasmolysis, crenation or lysis in hypertonic and hypotonic media
  • interpret zero-mass-change graphs and identify isotonic conditions in plant or animal cell experiments

Covered syllabus points

D2.3.1—Solvation with waterD2.3.2—Water movementD2.3.3—Osmosis into/out of cellsD2.3.4—Changes in plant tissueD2.3.5—Effects on cells without wallD2.3.6—Effects on cells with wallD2.3.7—Medical applications

D2.3 Water potential question 1

[Maximum number: 2]

Question (a)

(a)

A study was done on the osmolarity of semen and sperm movement (motility).

Figure for Question (a) — IB Biology SL
[ 1 ]

Question (i)

(i)

The same study showed that blood plasma has a lower osmolarity than semen. Explain how that would affect the movement of water between blood plasma and semen.

[ 1 ]

Question (b)

(b)

Explain a change that would take place in sperm placed in a hypotonic solution.

[ 1 ]

D2.3 Water potential question 2

[Maximum number: 3]

The electron micrograph shows the surface membrane of an animal cell.

Figure for Question D2.3 Water potential question 2 — IB Biology SL

Explain the reason that animal cells and tissues under investigation must be maintained in solutions with the same osmolarity.

D2.3 Water potential question 3

[Maximum number: 5]

An experiment was carried out to determine the change in mass due to osmosis. Potato cubes were soaked in different concentrations of sodium chloride for 12 hours. The table shows the mean data for the mass of potato before and after the 12-hour period.

Table for Question D2.3 Water potential question 3 — IB Biology SL

Question (a)

(a)

Outline the conditions necessary for osmosis to occur.

[ 2 ]

Question (b)

(b)

Explain how the data may be used to determine the solute concentration of the potato tissue.

[ 2 ]

Question (c)

(c)

Estimate the solute concentration of the potato tissue.

[ 1 ]
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