Question

When partial pressure of \(\mathrm{CO}_{2}\left(\mathrm{pCO}_{2}\right)\) rises, the oxygen dissociation curve of haemoglobin at \(37^{\circ} \mathrm{C}\) will (a) Shift towards right (b) Shift towards left (c) Become irregular (d) Remains unchanged

Short answer

When the partial pressure of CO2 rises, the oxygen dissociation curve of haemoglobin at \(37^{\circ} \mathrm{C}\) shifts to the right.

Step-by-step solution

Analyzing the Oxygen Dissociation Curve

The Bohr effect explains how carbon dioxide and pH affect the oxygen dissociation curve of hemoglobin. When the partial pressure of CO2 (pCO2) rises, it results in the production of more hydrogen ions, lowering the pH (or increasing acidity) in the blood and reducing the affinity of hemoglobin for oxygen.

Mapping the Effect of pCO2 Changes

An increase in the pCO2 shifts the oxygen dissociation curve to the right, indicating a lower affinity of hemoglobin for oxygen at the same partial pressure of oxygen. This is because a rise in CO2 concentration makes the blood more acidic, and under these conditions, hemoglobin binds less tightly to oxygen.

Identifying the Right Option

Given the explanations provided above, we can determine how the oxygen dissociation curve of hemoglobin at \(37^{\circ} \mathrm{C}\) will change when the pCO2 level rises. The correct option in this case is (a) - the curve shifts to the right.

Key concepts

Oxygen Dissociation Curve

The oxygen dissociation curve is a graphical representation used to understand how hemoglobin in blood releases and binds oxygen. This curve essentially plots the percentage saturation of hemoglobin against the partial pressure of oxygen in blood. It is typically 'S'-shaped (sigmoidal) because of the cooperative binding nature of hemoglobin.
As one molecule of oxygen binds to hemoglobin, it changes the shape of the hemoglobin, making it easier for more oxygen to bind. This is why the curve starts off relatively flat at lower oxygen pressures and then steepens.
The oxygen dissociation curve provides critical insights into how blood carries and releases oxygen in response to varying conditions, such as exercise or different partial pressures of carbon dioxide.

Partial Pressure of CO2

The partial pressure of CO2 (pCO2) is a measurement of carbon dioxide pressure in the blood, which affects the body's acid-base balance. It plays a critical role in regulating blood pH levels.
When pCO2 levels rise, it causes an increase in hydrogen ion concentration due to the reaction: \[ \mathrm{CO}_2 + \mathrm{H}_2\mathrm{O} \leftrightarrow \mathrm{H}_2\mathrm{CO}_3 \leftrightarrow \mathrm{H}^+ + \mathrm{HCO}_3^- \]This results in a more acidic environment.
The body's respiratory system carefully manages pCO2 levels to maintain homeostasis. In the context of the Bohr effect, an increase in pCO2 leads to the oxygen dissociation curve shifting to the right, which indicates a reduced affinity of hemoglobin for oxygen.

Hemoglobin Affinity

Hemoglobin affinity for oxygen refers to how tightly hemoglobin holds onto oxygen molecules. It is crucial for effective oxygen transport from the lungs to tissues throughout the body.
Several factors influence hemoglobin's affinity for oxygen, including temperature, pH, and levels of CO2. During the Bohr effect, increased CO2 and hydrogen ions result in a reduced affinity of hemoglobin for oxygen, facilitating oxygen release in tissues that require it the most.
Understanding hemoglobin affinity is important for medical conditions and treatments. For instance, patients with respiratory diseases may experience changes in hemoglobin affinity due to altered levels of CO2 and oxygen.

Blood Acidity

Blood acidity, measured by pH, is a crucial component of the body's overall metabolic balance. The normal pH of human blood is slightly alkaline, around 7.4.
This delicate balance can be disrupted by various factors, including CO2 levels. Higher levels of CO2 contribute to increased hydrogen ion concentration, making the blood more acidic (lowering the pH).
In the Bohr effect, this increase in acidity reduces hemoglobin's affinity for oxygen, essential for efficient oxygen delivery to tissues during times of increased metabolic demand.

• Acidosis: An overly acidic blood condition. Can be caused by high pCO2.
• Alkalosis: An overly basic blood condition. Can result from excessively low pCO2.

Maintaining the correct pH is critical for proper physiological function and health.