Which one of the following conditions will favour maximum dissociation of oxygen from the oxyhaemoglobin in the tissues?
Show Hint
Think of "active muscle conditions" to remember oxygen unloading.
An active muscle is warm (higher temperature) and acidic (higher [$H^+$] from lactic acid and $CO_2$).
These identical conditions are what trigger hemoglobin to release its oxygen.
Step 1 : Understanding the Question:
This question tests the understanding of the factors that control the binding affinity between oxygen and hemoglobin, specifically focusing on the conditions that promote the release (dissociation) of oxygen in active tissues. Step 2 : Key Formulas and Approach:
The approach involves applying the principles of the oxygen-hemoglobin dissociation curve and the Bohr effect.
Factors that decrease hemoglobin's affinity for oxygen shift the dissociation curve to the right, facilitating oxygen unloading in tissues. Step 3 : Detailed Explanation:
• In metabolically active tissues, high rates of cellular respiration consume oxygen and produce carbon dioxide ($CO_2$) and heat.
• Effect of [$H^+$] (Bohr Effect): Increased $CO_2$ reacts with water to form carbonic acid, which dissociates into bicarbonate and hydrogen ions ($H^+$).
• This increases the concentration of hydrogen ions (higher [$H^+$] lower pH). These protons bind to hemoglobin, altering its conformation and reducing its affinity for oxygen, promoting oxygen release.
• Effect of Temperature: An increase in temperature (higher temperature) due to metabolic heat also destabilizes the bond between oxygen and hemoglobin, facilitating dissociation.
• Conversely, lower temperature and lower [$H^+$] (higher pH) stabilize the oxyhemoglobin state, which is characteristic of the lungs where oxygen loading occurs. Step 4 : Final Answer:
Thus, the combination of higher [$H^+$] and higher temperature promotes maximum oxygen dissociation.
This matches Option (A).
