Transport of Carbon Dioxide in the Blood

Transport of carbon dioxide in the blood occurs by three main methods: dissolved in plasma, bound to hemoglobin, and as bicarbonate ions. Respiration is a biological process that involves the activity of interchanging oxygen and carbon dioxide through a liquid medium to use the oxygen for the oxidation of glucose inside the mitochondria.

In this article, we will cover how carbon dioxide is transported in the blood.

We breathe in air (with oxygen) through our nose/mouth. In the lungs, thin air sacs (alveoli) are close to blood vessels. Oxygen moves from the air sacs into the blood, while carbon dioxide exits the blood and goes into the air sacs to be exhaled. This carbon dioxide waste from our cells travels in the blood to the lungs for exhalation.

Let’s read in detail how carbon dioxide is transported in blood.

When the process of cell respiration is completed, tissues produce carbon dioxide as an end product. After that, carbon dioxide from the cells disperses into blood and interchange with the oxygen present in blood under normal resting conditions. About 3.7 ml of carbon dioxide reaches 100 ml of blood. It is carried by both plasma and hemoglobin of blood.

Blood transport carbon dioxide in three ways:

Transport of Carbon Dioxide in the Blood as Carbonic Acid

Around 7% of carbon dioxide (CO2) travels in the blood dissolved directly in blood plasma. This dissolved CO2 contributes about 0.3 milliliters (ml) per deciliter (dL) of blood. The amount of dissolved CO2 also affects the blood’s CO2 tension, which reflects the pressure exerted by CO2.

CO₂ + H₂O——————–> H₂CO₃

This reaction mostly takes place in red blood cells (RBCs) because it is catalyzed by a zinc-activated enzyme, carbonic anhydrase, and that is stimulated by low PO2 at the cellular level.

Also Read: Full Form of RBC

Transport of Carbon Dioxide in the Blood as Bicarbonates of Sodium and Potassium

Around 70% of carbon dioxide is carried in the blood as bicarbonate ions (HCO^3-). Inside red blood cells (RBCs), carbonic acid (H₂CO₃) forms from CO₂ and water. This carbonic acid quickly breaks down into bicarbonate ions and hydrogen (H⁺) ions. Most bicarbonate ions then leave the RBCs and enter the blood plasma, while chloride ions (Cl^–) move from the plasma into the RBCs in exchange. This maintains electrical neutrality within the cells.

This swapping of bicarbonate and chloride ions is called the chloride shift or Hamburger shift. A protein in RBCs called the bicarbonate-chloride carrier facilitates this exchange, allowing the ions to move in opposite directions.

H₂CO₃ ———————> H⁺ + HCO₃^–

K. Hb ————————> K⁺ + Hb^–

(In RBC) K⁺ + HCO_3- ————-> KHCO₃

(In plasma) Na⁺ + HCO₃ ————> NaHCO₃

Transport of Carbon Dioxide in the Blood as Carbaminohaemoglobin

About 23% of CO₂ is transferred as carbaminohaemoglobin which is made by a reversible combo of CO₂ with amino groups (globin part) of hemoglobin. Its emergence is leaned by high PCO₂ and low PO₂ at the level of body tissues.

Hb^– + H+ ————> H -Hb (Haemoglobin acidic)

H. Hb + CO₂ ————–> CO_{2 .} H Jb (Carbaminohaemoglobin)

Reversible compounds are bicarbonates, carbonic acid, and Carbaminohaemoglobin and which are formed in the presence of low PO₂ ad low acidic hemoglobin at a cellular level. Such compounds detached at the lung level, where high PO₂ prefers dissociation of carbonic acid and acidic oxyhemoglobin by carbonic anhydrase enzyme. Now, carbon dioxide becomes free to be interchanged with oxygen during external respiration.

The transport of gases, particularly carbon dioxide, in the blood is a critical process that ensures the removal of metabolic waste from the body. Carbon dioxide is transported in three main forms: dissolved in plasma, as bicarbonate ions, and bound to hemoglobin as carbaminohemoglobin. These mechanisms facilitate efficient gas exchange, allowing carbon dioxide produced by cellular respiration to be carried to the lungs for exhalation.

Also Read:

• Transport of Oxygen
• Exchange Of Gases Notes CBSE Class 11
• Regulation Of Respiration
• Facts About Blood
• NCERT Notes Class 11 Biology Chapter 14 – Breathing and Exchange of Gases

What is the Most Common Method of Carbon Dioxide Transport?

The most common method of carbon dioxide transport is as bicarbonate ions, which accounts for about 70% of the total CO2 carried in the blood.

How is Carbon Dioxide Transported in the Blood?

Carbon dioxide is transported in the blood in three ways: dissolved in plasma, as bicarbonate ions, and bound to hemoglobin as carbaminohemoglobin.

Where does Carbon Dioxide in our Blood Come From?

Carbon dioxide in our blood comes from the metabolic processes of cells, where it is produced as a waste product during cellular respiration.

What is the Transport of CO₂ by Blood Primarily Dependent Upon?

The transport of CO₂ by blood is primarily dependent upon its conversion to bicarbonate ions, facilitated by the enzyme carbonic anhydrase in red blood cells.