Transport of Gases – Oxygen and Carbon Dioxide

Transport of Gases – Oxygen and Carbon Dioxide

The transport of oxygen and carbon dioxide in the blood occurs through distinct processes, each of which has unique physiological processes. In oxygen transportation, the gas is bound to the protein hemoglobin that is found in the blood, whereby each molecule of this protein binds up to four molecules of oxygen, forming oxyhemoglobin. On the other hand, carbon dioxide has three main forms through which it is transported in the blood: carbonic acid, carbamino compounds, and dissolved gas. Carbonic acid is formed as a result of carbon dioxide being hydrated by water, and the products are bicarbonate and hydrogen ions, which take up about 90% of the carbon dioxide.  Of the remaining 10%, approximately 5% binds to the amino groups of plasma proteins and hemoglobin to create carbamino compounds—primarily carbaminohemoglobin (HbCO2) (Saladin, Gan & Cushman, 2010). Subsequently, the remaining carbon dioxide is carried as a dissolved gas.

            Several factors affect the transport of oxygen and carbon dioxide. The first is temperature, whereby high temperatures reduce hemoglobin’s affinity for oxygen. As a result, more oxygen is released in the tissues, i.e., the right shift in the oxygen dissociation curve. Conversely, in low temperatures, a left shift occurs whereby hemoglobin’s affinity for oxygen increases, resulting in more oxygen loading in the lungs (Saladin, Gan & Cushman, 2010). For carbon dioxide, high temperature increases its production by the tissues, meaning more gas uploads are needed. The second factor is pH, whereby in acidic conditions, or rather reduced pH, a right shift occurs because the affinity of oxygen by hemoglobin decreases. This is because more hydrogen ions weaken the bond between oxygen and hemoglobin. The opposite happens in more alkaline conditions. In regards to carbon dioxide, acidic conditions can lead to an increase in the conversion of the gas to bicarbonate.

The third factor is BPG, which, when it increases, leads to an increase in oxygen unloading in tissues. Since red blood cells have no mitochondria, they rely on anaerobic fermentation, and PG is one of the components needed for this (Saladin, Gan & Cushman, 2010). Thus, an increase in BPG results in more energy produced, hence more oxygen unloading. Notably, BPG does not directly affect carbon dioxide transport; however, it indirectly affects CO2 production and unloading in tissues by influencing oxygen release. Lastly, yet importantly, PCO₂ also affects oxygen and carbon dioxide loading and unloading. High levels of PCO2 result in a right shift because the hemoglobin’s affinity for oxygen is reduced and vice versa (Powell Jr, 2003).  PCO₂ also affects the loading and unloading of carbon dioxide because high PCO₂ levels increase the formation of bicarbonate, while low levels of PCO2 lead to the opposite effect, and the gas is released in the lungs.

Conclusively, temperature, pH, BPG, and PCO2 dynamically regulate the blood’s loading and unloading of oxygen and carbon dioxide. These factors ensure efficient gas exchange and adjust to the body’s varying metabolic demands.

References

Powell Jr, F. L. (2003). Oxygen and carbon dioxide transport in the blood. Essential Medical Physiology, 289-298.

Saladin, K. S., Gan, C. A., & Cushman, H. N. (2010). Anatomy & physiology: the unity of form and function (Vol. 5). New York: McGraw-Hill.

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Transport of Gases – Oxygen and Carbon Dioxide

Describe how oxygen and carbon dioxide are transported in the blood, and explain how their loading and unloading is affected by temperature, pH, BPG, and PCO2.