Transport of Carbon Dioxide

By: Kimberly Walsh

Carbon dioxide Transport •Carbon Dioxide is transported in the blood by three ways:

Dissolved CO2- 10% Bound to Hemoglobin (Hb)-20% HCO3 –Bicarbonate -70%

CARBON DIOXIDE• DISSOLVED CO2• Carbon dioxide is more soluble in blood than is oxygen; about 10% of all

carbon dioxide is dissolved in the plasma

• BOUND TO HAEMOGLOBIN• When carbon dioxide binds to hemoglobin, a molecule called 

carbaminohemoglobin is formed. Binding of carbon dioxide to hemoglobin is reversible. Therefore, when it reaches the lungs, the carbon dioxide can freely dissociate from the hemoglobin and be expelled from the body

• CO2 + Hb HbNHCOOH

Carbon dioxide Transport• HCO3 – BICARBONATEMajority of carbon dioxide molecules ( 70 percent) are carried as part of the bicarbonate buffer system. In this system, carbon dioxide diffuses into the red blood cells. Carbonic anhydrase (CA) within the red blood cells quickly converts the carbon dioxide into carbonic acid (H2CO3). Carbonic acid is an unstable, intermediate molecule that immediately dissociates into bicarbonate ions (HCO3

−) and hydrogen (H+) ions. Since carbon dioxide is quickly converted into bicarbonate ions, this reaction allows for the continued uptake of carbon dioxide into the blood, down its concentration gradient. It also results in the production of H+ ions. If too much H+ is produced, it can alter blood pH.

Carbon dioxide• However, hemoglobin binds to the free H+ ions, limiting shifts in pH. The

newly-synthesized bicarbonate ion is transported out of the red blood cell into the liquid component of the blood in exchange for a chloride ion (Cl-); this is called the chloride shift. When the blood reaches the lungs, the bicarbonate ion is transported back into the red blood cell in exchange for the chloride ion. The H+ ion dissociates from the hemoglobin and binds to the bicarbonate ion. This produces the carbonic acid intermediate, which is converted back into carbon dioxide through the enzymatic action of CA. The carbon dioxide produced is expelled through the lungs during exhalation

Carbon dioxide

• CO2+H2O =H2CO3 = H +HCO3

CARBON DIOXIDE TRANSPORT

• HALDANE EFFECT- Increase in O2 cause the release of CO2 from the hemoglobin into the lungs.

• This means that when oxygen is bound to haemoglobin its affinity for carbon dioxide is reduced.

CARBON DIOXDE TRANSPORT

Carbon Dioxide transport

• If ventilation increases additional CO2 is exhaled and hydrogen concentration is lowered

• If ventilation is reduced then the CO2 will build up and the hydrogen concentration will increase

CARBON DIOXIDE

• The transport of CO2 has an important role in the acid-base status of the blood and maintenance of normal homeostasis

CARBON DIXIODE TRANSPORT• Respiratory Acidosis• Respiratory acidosis occurs when too much CO2 builds up in the

body and there is a decrease in the pH. Normally the lungs remove CO2 while you breathe. However, sometimes your body can’t get rid of enough CO2. This may happen because of:

• chronic airway conditions, like asthma• injury to the chest• obesity, which can make breathing difficult• muscle weakness in the chest

CARBON DIOXIDE TRANSPORT

• Problems with the nervous system• Deformed chest structure

CARBON DIOXIDE TRANSPORT

• Respiratory AlkalosisHyperventilation or excessive ventilation causes rapid elimination of C02 from the blood. This results in a decreased PCO2 and an increased pH. Respiratory alkalosis occurs when there isn’t enough carbon dioxide in your bloodstream. It’s often caused by: • hyperventilation, which commonly occurs with anxiety

CARBON DIOXIDE

• Lack of Oxygen• Being in high altitudes• Lung Disease

Additional Notes

• Compensated Respiratory Acidosis – Increase in CO2 levels however in this case the pH level remains the same.

• Compensated Respiratory Alkalosis- Decrease in CO2 levels however in this case the pH level remains the same.

THE END