CO2 Transport | Carbon-di-oxide Transport | Respiratory Gas Exchange | Respiratory Physiology

Summary

This Bite Size Med video explains carbon dioxide transport in the blood. Carbon dioxide, a byproduct of tissue metabolism, is transported in three forms: dissolved (5%), bound to hemoglobin as carbaminohemoglobin (20%), and chemically modified as bicarbonate (70%). The video highlights the Bohr and Haldane effects, which regulate oxygen and carbon dioxide exchange. It also details the role of carbonic anhydrase in forming carbonic acid, the chloride shift, and how oxygenation of hemoglobin promotes carbon dioxide release for expiration.

Takeaways

• 🌟 The purpose of respiration is gas exchange, where oxygen enters the bloodstream and carbon dioxide is expelled.
• 🔍 Carbon dioxide in the pulmonary capillaries originates from mixed venous blood, which carries waste from body tissues.
• 🏃‍♂️ Tissue metabolism produces carbon dioxide as a byproduct when using oxygen.
• 💧 Dissolved carbon dioxide constitutes about 5% of its transport in the blood, being more soluble than oxygen.
• 🩸 The bound form of carbon dioxide is carbaminohemoglobin, accounting for approximately 20%, and it affects oxygen binding.
• 🔄 The Bohr effect describes how carbon dioxide binding to hemoglobin reduces its oxygen affinity, shifting the oxygen dissociation curve rightward.
• 🔄 The Haldane effect explains how the removal of oxygen from hemoglobin increases its affinity for carbon dioxide.
• 🧪 The most significant form of carbon dioxide transport is chemically modified as bicarbonate ions, about 70%.
• 🔄 Carbon dioxide reacts with water in the presence of carbonic anhydrase to form carbonic acid, which then dissociates.
• 🔄 The chloride-bicarbonate exchange, or chloride shift, maintains ionic balance as bicarbonate leaves red blood cells for chloride.
• 💡 Hemoglobin buffers hydrogen ions to prevent an acidic environment and maintains blood pH.

Q & A

What is the primary purpose of respiration?

The primary purpose of respiration is gas exchange, where oxygen enters the capillary from the alveolus and carbon dioxide leaves the capillary to enter the alveolus and is then breathed out.

Where does the carbon dioxide in the pulmonary capillaries come from?

The carbon dioxide in the pulmonary capillaries comes from mixed venous blood that arrives via the pulmonary artery, which in turn receives blood from all the body tissues.

How is carbon dioxide produced in the body?

Carbon dioxide is produced during tissue metabolism, where tissues use oxygen and form carbon dioxide as a byproduct.

In what three forms is carbon dioxide transported in the blood?

Carbon dioxide is transported in the blood in three forms: dissolved carbon dioxide, bound form as carbaminohemoglobin, and chemically modified form as bicarbonate.

What percentage of carbon dioxide is transported as dissolved carbon dioxide?

About five percent of carbon dioxide is transported as dissolved carbon dioxide, which is more soluble than oxygen.

How does carbon dioxide bind to hemoglobin and what is the effect on oxygen affinity?

Carbon dioxide binds to hemoglobin at the n-terminus of the globin chain, forming carbaminohemoglobin. This binding reduces hemoglobin's affinity for oxygen, which is known as the Bohr effect.

What is the Haldane effect and how does it relate to oxygen and carbon dioxide binding to hemoglobin?

The Haldane effect is the phenomenon where the binding of oxygen to hemoglobin lowers its affinity for carbon dioxide. Conversely, if less oxygen is bound, there's a higher affinity for carbon dioxide.

What is the most important form in which carbon dioxide is transported in the blood and what percentage does it represent?

The most important form in which carbon dioxide is transported is as bicarbonate, accounting for around 70 percent of its transport in the blood.

How does the chloride shift or anion exchange protein Band 3 contribute to carbon dioxide transport?

The chloride shift, facilitated by the anion exchange protein Band 3, allows bicarbonate to leave the red blood cell to maintain ionic balance, and chloride enters in exchange, which is crucial for the transport of carbon dioxide.

How does hemoglobin buffer hydrogen ions to maintain blood pH?

Hemoglobin buffers hydrogen ions to prevent an acidic environment, thus maintaining the pH of the red blood cells and blood. This is important for the proper functioning of the blood's transport mechanisms.

What happens to carbon dioxide in the pulmonary capillaries during oxygenation of hemoglobin?

During oxygenation of hemoglobin in the pulmonary capillaries, hydrogen ions dissociate from hemoglobin, and bicarbonate enters the red blood cell in exchange for chloride. This leads to the formation of carbonic acid, which then dissociates into carbon dioxide and water, with carbon dioxide being exhaled.

How does the concentration of carbon dioxide in the blood depend on tissue metabolism and alveolar ventilation rate?

The concentration of carbon dioxide in the blood depends on the rate of its production through tissue metabolism and the rate at which it is expired through alveolar ventilation.