During maximal exercise, a trained athlete can achieve cardiac outputs of 25-30 L/min. Oxygen extraction from blood increases substantially. The Bohr effect facilitates peripheral O2 unloading during exercise because increased muscle CO2 production:

• A Directly competes with O2 for the heme iron binding site on hemoglobin
• B Stimulates 2,3-BPG synthesis in erythrocytes within seconds of exercise onset
• C Increases local temperature independently of acid-base changes
• D Lowers pH, reducing hemoglobin-O2 affinity and shifting the oxyhemoglobin dissociation curve rightward ✓

Explanation

The Bohr effect describes the rightward shift in the oxyhemoglobin dissociation curve caused by increased CO2 and H+ (reduced pH). Active muscles produce CO2 and lactic acid, lowering local pH. At acidic pH, protonation of histidine residues on hemoglobin stabilizes the T (tense, deoxy) conformation, reducing O2 affinity and facilitating unloading of O2 to tissues. This is a rapid, direct, allosteric effect distinct from the slower 2,3-BPG-mediated shift, which occurs over hours of sustained hypoxia or high altitude adaptation.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.