Transport of oxygen and carbon dioxide
Transport of oxygen and carbon dioxide
Transport of Oxygen
Formation of Oxyhaemoglobin
- Oxygen from the air we breathe diffuses into the blood in the capillaries surrounding the alveoli in the lungs.
- This oxygen is taken up by haemoglobin in red blood cells, forming oxyhaemoglobin.
Oxygen Transport
- Oxyhaemoglobin carries oxygen through the bloodstream to the body’s cells.
- When the red blood cells reach the body’s cells, the oxyhaemoglobin breaks down, releasing the oxygen.
- This oxygen then diffuses across the cell membrane to be used in the process of cellular respiration.
Transport of Carbon Dioxide
Formation of Carbaminohaemoglobin
- Cells produce carbon dioxide as a waste product of cellular respiration.
- A small quantity of CO2 can bind with haemoglobin to form carbaminohaemoglobin.
Carbon Dioxide in Plasma
- Most of the carbon dioxide produced by cells diffuses out into the blood and is carried in plasma as bicarbonate ions, after reacting with water in the presence of an enzyme called carbonic anhydrase.
Carbon Dioxide Exhalation
- When blood rich in bicarbonate ions reaches the lungs, this reaction is reversed, forming carbon dioxide and water.
- This allows carbon dioxide to diffuse out of the capillaries surrounding the alveoli in the lungs and be exhaled.
Role of Carbonic Anhydrase
- The enzyme carbonic anhydrase, found in red blood cells, catalyses the conversion of carbon dioxide and water to carbonic acid.
- This carbonic acid then quickly dissociates into a hydrogen ion and a bicarbonate ion.
Oxygen and Carbon Dioxide in the Respiratory System
- The diffusion of gases in the respiratory system, including oxygen and carbon dioxide, is facilitated by the thin walls of the alveoli and capillaries, the moist surfaces for gas exchange, and the large surface area provided by the numerous capillaries around each alveolus.
- The diffusion gradient is maintained by the constant movement of blood and inhalation and exhalation of air from the lungs.