IB DP Biology Mock Exam HL Paper 1B Set 3 - 2025 Syllabus
IB DP Biology Mock Exam HL Paper 1B Set 3
Prepare for the IB DP Biology Exam with our comprehensive IB DP Biology Exam Mock Exam HL Paper 1B Set 3. Test your knowledge and understanding of key concepts with challenging questions covering all essential topics. Identify areas for improvement and boost your confidence for the real exam
Question
▶️ Answer/Explanation
(a)
From the graph, haemoglobin saturation at 40 mmHg is about 73%.
(Accept values between 71–74%.)
(b)
• As pO2 increases, the percentage saturation also rises — a positive correlation.
• At higher pO2 values (around 70–100 mmHg), the curve begins to plateau as haemoglobin approaches full saturation.
• The relationship is sigmoidal (S-shaped) due to cooperative binding of oxygen.
(c)
The foetal curve should be drawn: • to the left of the adult curve • with the same general sigmoidal shape
This indicates that foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin.
(d)
Examples of suitable adaptations:
• Haemoglobin contains four haem groups, each able to bind one O2.
• Cooperative binding: once one O2 binds, haemoglobin’s affinity for oxygen increases.
• Iron (Fe²⁺) in each haem group binds oxygen reversibly, enabling loading and unloading depending on pO2.
(e)
Tidal volume can be measured by:
• Asking the subject to breathe normally into a spirometer or suitable lung-volume device.
• Recording the change in volume on the spirometer trace during one unforced breath.
• Calculating the volume of air moved in or out by measuring the height of one “normal breath” on the trace.
Accept: water spirometer, bell jar apparatus, balloon-type volume measurement devices.