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IB Biology HL B2.1.5 Osmosis and Aquaporins Question Bank

Practise IB Biology HL B2.1.5 through questions that extend osmosis into aquaporin regulation, gradients and data interpretation.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Analyse aquaporin and water-potential data to explain osmosis rates and net movement.
  • Compare frog cells with aquaporin mRNA and controls using membrane-permeability evidence.

B2.1.5—Osmosis and aquaporins question 1

[Maximum number: 3]

In the early 1990s, investigations involving egg cells from the African clawed frog (Xenopus laevis) led to the discovery of membrane channel proteins called aquaporins.

In one investigation, scientists injected 10 frog egg cells with a solution containing mRNA encoding for an aquaporin, and another 10 frog egg cells with distilled water (control cells). All the frog egg cells were then incubated in a hypotonic solution. The volume of the frog egg cells was then measured during a period of five minutes.

The graph shows the mean results of the investigation.

Figure for Question B2.1.5—Osmosis and aquaporins question 1 — IB Biology HL

Question (a)

(a)

State the direction of net movement of water across the plasma membrane of all the frog egg cells between 0 and 3 minutes.

[ 1 ]

Question (b)

(b)

Explain the reasons for the different results obtained for the frog egg cells with aquaporin mRNA and the control frog egg cells.

[ 2 ]
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