Question

Most carbon dioxide is transported in what part of the blood, and in what form? Explain the function of hemoglobin with respect to carbon dioxide transport. (p. 359)

Short answer

Explain the role of hemoglobin in this process. Answer: Most carbon dioxide is transported in the blood plasma as bicarbonate ions (HCO3-). Hemoglobin plays a crucial role by binding to hydrogen ions and a small amount of carbon dioxide directly, maintaining the blood's pH levels and aiding in the transportation of carbon dioxide.

Step-by-step solution

Part of the blood where most carbon dioxide is transported

Most of the carbon dioxide is transported in the blood plasma, which is the liquid portion of the blood.

Form of carbon dioxide transportation

Carbon dioxide is not transported in its gaseous state in the blood. Instead, it is converted to a molecule called bicarbonate (HCO3-) through a series of chemical reactions.

Carbon dioxide transport process

When carbon dioxide diffuses into the blood from tissues, it reacts with water to form carbonic acid (H2CO3), a weak acid. This reaction is catalyzed by an enzyme called carbonic anhydrase. Carbonic acid then dissociates into a hydrogen ion (H+) and a bicarbonate ion (HCO3-). Most of the bicarbonate ions are transported in the plasma, while hydrogen ions combine with hemoglobin.

Function of hemoglobin with respect to carbon dioxide transport

Hemoglobin not only plays a role in oxygen transportation but also has an essential role in carbon dioxide transport. As mentioned earlier, hydrogen ions resulting from the dissociation of carbonic acid combine with hemoglobin, forming a compound called carbaminohemoglobin. This process reduces the acidity of the blood and is known as the "Haldane effect." Hemoglobin acts as a buffer, preventing significant changes in blood pH levels. Additionally, a small percentage of carbon dioxide can bind directly to hemoglobin, further aiding in its transport. In summary, most carbon dioxide is transported in the blood plasma as bicarbonate ions, and hemoglobin plays a crucial role in maintaining the blood's pH levels by binding to hydrogen ions and a small amount of carbon dioxide directly.