Question

Describe three ways in which carbon dioxide can be transported.

Short answer

Answer: The three ways in which carbon dioxide is transported in the body are: 1. Bicarbonate (HCO3-) ions in plasma 2. Bound to hemoglobin as carbaminohemoglobin 3. Dissolved in blood plasma.

Step-by-step solution

1. Bicarbonate (HCO3-) ions in plasma

The most common method of carbon dioxide transport in the body is through bicarbonate (HCO3-) ions in plasma. When carbon dioxide dissolves in blood plasma, it reacts with water to form carbonic acid (H2CO3), which then dissociates into bicarbonate ions (HCO3-) and protons (H+). This reaction is catalyzed by the enzyme carbonic anhydrase, present in red blood cells. The bicarbonate ions can then be transported through the bloodstream to the lungs, where they are converted back to carbon dioxide and expelled from the body.

2. Bound to hemoglobin

Carbon dioxide can also be transported in the form of carbaminohemoglobin, which involves binding with the protein hemoglobin in red blood cells. Hemoglobin can bind to both oxygen (forming oxyhemoglobin) and carbon dioxide (forming carbaminohemoglobin) but has a higher affinity for oxygen. When oxygen levels in the blood are low, hemoglobin releases oxygen and binds to carbon dioxide, forming carbaminohemoglobin. This process enables the safe transport of carbon dioxide to the lungs, where it is released and expelled during exhalation.

3. Dissolved in plasma

A small portion of carbon dioxide remains dissolved in the blood plasma. This dissolved CO2 can diffuse from the body's tissues, where it is produced, into the bloodstream, and then back out into the lungs, where it can be exhaled. Although this method accounts for only a small percentage of the total CO2 transported in the blood (approximately 7%), it still plays a vital role in maintaining proper gas exchange and acid-base balance in the body.