Comparing Bohr Effect in Cat and Human Haemoglobin Curves

Steps:

• Identify standard (pH 7.4) and Bohr-shifted (low pH) curves for both haemoglobins on the graph.
• Note oxygen affinity by curve position: leftward shift indicates higher affinity (lower P50).
• Measure horizontal shift (ΔP50) between standard and low-pH curves for each type.
• Compare ΔP50 values: cat shows larger shift than human.

Why C is correct:

• The Bohr effect is quantified by the rightward shift in the oxygen dissociation curve (increased P50) at low pH due to H+ binding; cat haemoglobin's greater ΔP50 confirms a larger effect.

Why the others are wrong:

• A: At high PO2 (>80 mmHg), cat curve is right-shifted vs. human, indicating lower, not greater, affinity.
• B: At low PO2 (<20 mmHg), human curve is left of cat's, so human picks up oxygen more easily.
• D: Not enough information (option incomplete).

Final answer: C