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Edexcel A-Level Biology AS 2.4 Osmosis and Water Potential Gradients Questions

Compare solute concentration and water potential on both sides, predict net water movement through partially permeable membranes, and explain mass or volume changes in cells and tissues.

Syllabus
First assessment 2019
Course
Biology YBI11
Level
AS

Exam points

  • Define osmosis through free-water movement down a water-potential gradient across a partially permeable membrane.
  • Predict net water movement and equilibrium by comparing water potential or solute concentration on each side.
  • Design and interpret osmosis investigations using mass or volume change, repeats and water-potential evidence.

Edexcel A-Level Biology AS 2.4 Osmosis and Water Potential Gradients Questions question 1

[Maximum number: 5]

In an investigation, the water potential of a potato was compared with that of a yam.

Question (a)

(a)

State what is meant by the term water potential.

[ 2 ]

Question (b)

(b)

The graph shows the results obtained in this investigation.

Figure for Question (b) — Edexcel A-Level Biology AS
[ 3 ]

Question (i)

(i)

Different concentrations of sucrose solutions have different water potentials.

The graph shows the water potentials for sucrose solutions of different concentrations.

Determine the water potential for the potato cylinders.
Use your completed graph and this graph to determine the water potential.

Figure for Question (i) — Edexcel A-Level Biology AS

Value read from completed graph
Water potential of the potato
kPa

[ 2 ]

Question (ii)

(ii)

The water potential for the yam was -1890 kPa .

Suggest why there is a difference between the water potential of the yam and the water potential of the potato.

[ 1 ]
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