Select the odd one w.r.t. factors responsible for favouring the dissociation of oxygen from oxyhaemoglobin.
Solution:
The dissociation of oxygen from oxyhaemoglobin is favoured by conditions typically found in metabolically active tissues, where oxygen is needed. These conditions include:
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High pCO2: Increased partial pressure of carbon dioxide leads to increased H+ concentration (due to carbonic acid formation), which lowers pH and shifts the oxygen dissociation curve to the right, favouring O2 release.
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High H+ concentration (Low pH): A decrease in pH (more acidic conditions) weakens the bond between oxygen and haemoglobin, promoting oxygen dissociation. This is known as the Bohr effect.
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High temperature: Increased temperature also reduces the affinity of haemoglobin for oxygen, leading to greater dissociation.
Looking at the options:
(1) Low pH: Favours dissociation.
(3) High H+ concentration: Equivalent to low pH, thus favours dissociation.
(4) High temperature: Favours dissociation.
(2) Low pCO2: A low partial pressure of carbon dioxide increases the affinity of haemoglobin for oxygen, thereby inhibiting dissociation and favouring oxygen binding (association). This condition is typically found in the alveoli of the lungs, where oxygen loading occurs. Therefore, low pCO2 is the odd one out as it does not favour the dissociation of oxygen from oxyhaemoglobin.