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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 or lysis when red blood cells are placed in distilled water or another hypotonic solution.
  • Interpret red-cell morphology or haemolysis data to distinguish hypotonic water gain from hypertonic crenation and water loss.
  • Explain how a freshwater protist uses increased contractile-vacuole activity to expel excess water in a dilute medium.

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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