Question

Which one of the following conditions will favour maximum dissociation of oxygen from the oxyhaemoglobin in the tissues?

• A. higher [$H^+$]; higher temperature
• B. higher [$H^+$]; lower temperature
• C. lower [$H^+$]; higher temperature
• D. lower [$H^+$]; lower temperature

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.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The binding of oxygen to hemoglobin is a reversible process governed by the oxygen-hemoglobin dissociation curve.
In metabolically active tissues, conditions change to facilitate the release (dissociation) of oxygen from oxyhemoglobin so cells can use it for respiration.
Step 2: Detailed Explanation:
Active tissues produce carbon dioxide ($CO_2$) and metabolic heat as waste products.
The increase in $CO_2$ causes a reaction with water that forms carbonic acid, which dissociates into bicarbonate and hydrogen ions, lowering the pH and raising the concentration of hydrogen ions ($[\text{H}^+]$).
According to the Bohr effect, an increase in $[\text{H}^+]$ (acidity) and an increase in temperature both decrease hemoglobin's affinity for oxygen.
This shifts the oxygen-hemoglobin dissociation curve to the right, weakening the bonds between oxygen and hemoglobin and maximizing oxygen unloading into the oxygen-depleted tissues.
Therefore, higher $[\text{H}^+]$ and higher temperature are the ideal conditions that promote maximum dissociation.
Step 3: Final Answer:
Maximum dissociation of oxygen from oxyhaemoglobin is favoured by higher $[\text{H}^+]$ and higher temperature.