Answer: Decreased pH, increased CO 2 , increased temperature, increased 2,3-BPG (decreased Hb-O 2 affinity, more O 2 released to tissues).
- A Increased blood pH combined with decreased CO<sub>2</sub> stabilizing the relaxed high-affinity state overall in most cases under typical conditions
- B Decreased pH, increased CO<sub>2</sub>, increased temperature, increased 2,3-BPG (decreased Hb-O<sub>2</sub> affinity, more O<sub>2</sub> released to tissues)
- C A fall in core body temperature that slows the hemoglobin conformational transition process according to standard textbooks
- D Replacement of adult HbA by fetal HbF circulating within the maternal bloodstream during pregnancy in general practice as frequently described
Correct answer: B. Decreased pH, increased CO<sub>2</sub>, increased temperature, increased 2,3-BPG (decreased Hb-O<sub>2</sub> affinity, more O<sub>2</sub> released to tissues)
Explanation: Right shift (decreased O<sub>2</sub> affinity): low pH, high CO<sub>2</sub>, high temperature, high 2,3-BPG. All occur in metabolically active tissues, ensuring O<sub>2</sub> release where needed most.
The S-shaped (sigmoid) curve reflects cooperative binding between Hb's four O₂ sites; the Bohr effect shifts the whole curve to the right under conditions found in actively respiring tissue (more CO₂, more acid, more heat), making haemoglobin release oxygen more readily exactly where it's needed.
Concept context
The mechanics of breathing, lung volumes, gas transport in blood, the Bohr effect, and respiratory regulation.