Explanation:

Transport of oxygen (O2) and carbon dioxide (CO2) in the blood is a crucial process for the proper functioning of the body. The pH of the blood plays a significant role in this process.

Acidic and alkaline conditions:

pH is a measure of the acidity or alkalinity of a substance. The pH scale ranges from 0 to 14, with 7 being neutral, less than 7 being acidic, and greater than 7 being alkaline. Blood pH is tightly regulated, with a normal range of 7.35 to 7.45.

Blood pH and transport of O2 and CO2:

The transport of O2 and CO2 in the blood is facilitated by the binding of these gases to hemoglobin (Hb) and other proteins. The binding of O2 to Hb is influenced by the pH of the blood. In an acidic environment, Hb has a higher affinity for O2, which means it binds more readily. On the other hand, in an alkaline environment, Hb has a lower affinity for O2, which means it releases O2 more readily.

Similarly, the transport of CO2 in the blood is also influenced by the pH of the blood. CO2 can combine with water (H2O) in the blood to form carbonic acid (H2CO3), which can then dissociate into hydrogen ions (H+) and bicarbonate ions (HCO3-). In an acidic environment, there are more H+ ions, which combine with HCO3- to form H2CO3 and release CO2. In an alkaline environment, there are fewer H+ ions, which means more HCO3- is available to combine with H+ ions and form H2CO3, which can then be converted back to CO2.

Slightly alkaline pH:

From the above explanation, it is clear that blood pH should be slightly alkaline (between 7.35 to 7.45) for the proper transport of O2 and CO2. This pH range ensures that Hb binds O2 readily in the lungs (where the pH is slightly more alkaline) and releases O2 readily in the tissues (where the pH is slightly more acidic). It also ensures that CO2 is released readily in the lungs (where the pH is slightly more acidic) and transported to the lungs as HCO3- (where the pH is slightly more alkaline).

Therefore, the correct answer is option 'D' (Slightly alkaline).

Because The oxygen-carrying capacity of hemoglobin determines how much oxygen is carried in the blood.

In addition, other environmental factors and diseases can also affect oxygen-carrying capacity and delivery; the same is true for carbon dioxide levels, blood pH, and body temperature.

When carbon dioxide is in the blood, it reacts with water to form bicarbonate (HCO 3 − ) and hydrogen ions (H + ). As the level of carbon dioxide in the blood increases, more H+ is produced and the pH decreases.

The increase in carbon dioxide and subsequent decrease in pH reduce the affinity of hemoglobin for oxygen. The oxygen dissociates from the Hb molecule, shifting the oxygen dissociation curve to the right.


Therefore, more oxygen is needed to reach the same hemoglobin saturation level as when the pH was higher.