Read When Haemoglobin Releases Oxygen
Haemoglobin loads oxygen in the lungs and unloads it in tissues as local conditions change.
Oxygen Transport is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Load in lungs, unload in tissues
Oxygen binding is reversible and responds mainly to PO2. High PO2 and low CO2/H+ favour loading; increased CO2 and H+ in active tissues lower affinity and promote unloading (Bohr effect).
Read a right shift
A right shift raises P50 and favours oxygen release. High CO2, high H+, high temperature and high 2,3-BPG shift right; lower temperature shifts left.
Apply curve shifts to physiology
Exercise raises CO2, H+, and temperature in working tissues, shifting the oxygen-dissociation curve right and aiding unloading. Fetal haemoglobin has higher oxygen affinity, giving a left shift. A left shift is not the expected acclimatory response to high altitude.
OlympIQ exam lens
- ✓O2 binding is reversible.
- ✓Bohr effect: higher H+/CO2 promotes unloading.
- ✓Right shift = higher P50 and easier tissue delivery.
CO2 modifies haemoglobin affinity but is not the primary ligand driving oxygen binding.
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