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← Theoretical 1

Q29 — The Bohr Effect — Oxygen-Haemoglobin Dissociation

Theoretical 1 Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Respiratory Physiology

The amount of oxygen transported by haemoglobin is affected by the partial pressure of oxygen and carbon dioxide. Under conditions of high partial pressure of carbon dioxide, the release of oxygen from oxyhaemoglobin is stimulated — the Bohr effect.

Graph of percentage haemoglobin oxygen saturation vs. partial pressure of oxygen, showing curves X and Y (the Bohr shift). Percentage saturation of haemoglobin with oxygen vs. partial pressure of oxygen — curve X (baseline) and curve Y (Bohr-shifted, rightward).

Using the information and graph, determine whether the following statements are true or false:

A. The change from X to Y is caused by a decrease in oxygen concentration and a high pH.
B. The change from X to Y is due to the decrease in oxygen concentration and low pH.
C. The change from X to Y is due to an increase in the concentration of carbon dioxide and low pH.
D. Y indicates the acclimation in the tissues of alpinists during high-altitude climbs.
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Question reproduced from IBO 2022, Theoretical Paper 1, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)