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IB Biology HL D2.3.5 Effects on Cells Without Wall Questions

Use osmotic mechanisms, cell morphology and haemolysis evidence to explain wall-less animal-cell responses and freshwater-protist regulation in IB Biology HL D2.3.5.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Predict water entry, swelling and lysis when animal cells are placed in a hypotonic or distilled-water solution.
  • Interpret red-cell morphology or haemolysis data to identify hypertonic or hypotonic effects, including crenation and water loss.
  • Explain how a freshwater protist responds to dilute medium by increasing contractile-vacuole activity to expel excess water.
  • Interpret how an external factor such as venom changes red-cell haemolysis across salt concentrations.

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Study D2.3.5—Effects on cells without wall conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Biology HL D2.3.5 Effects on Cells Without Wall Questions question 1

[Maximum number: 2]

Data was collected on rabbit red blood cells that were exposed to sodium chloride (NaCl) and scorpion venom. Under some osmotic conditions red blood cells swell and burst, releasing hemoglobin (hemolysis). The graph shows the response of red blood cells to different concentrations of sodium chloride, with and without scorpion venom.

Figure for Question IB Biology HL D2.3.5 Effects on Cells Without Wall Questions question 1 — IB Biology HL

Outline the effect of the venom on the hemolysis of red blood cells.

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