Explore how carbon dioxide from active tissues lowers pH, produces the Bohr shift and increases haemoglobin oxygen unloading during exercise in IB Biology HL B3.1.12.
Syllabus
First assessment 2025
Course
Biology HL
Level
HL
Exam points
Explain how CO₂ from respiring tissues lowers blood pH and haemoglobin affinity for oxygen.
Identify the Bohr shift as a rightward oxygen dissociation curve shift when CO₂ rises.
Use a right-shifted curve to explain increased O₂ release to active tissues at the same pO₂.
The graph shows the oxygen dissociation curve for adult hemoglobin.
[ 3 ]
Question (i)
(i)
Using the graph, draw a line to show how the oxygen dissociation curve changes with the Bohr shift.
[ 1 ]
partial pressure of oxygen
Question (ii)
(ii)
Explain the role of the Bohr shift during vigorous exercise.
[ 2 ]
a. more CO2 is produced which lowers the pH of the blood; b. hemoglobin releases more oxygen (at lower pH ) for same partial pressure of oxygen; c. more oxygen is available to respiring tissues;