Transport of CO2

The transportation of carbon dioxide plays a vital role in living beings. There are various CO2 transportation mechanisms in plants, animals and humans. CO2 is a metabolic consequence of carbohydrate metabolism, namely cellular respiration, in which carbohydrate or lipid is digested to provide metabolic energy like ATP (Adenosine Triphosphate). It is a chemical molecule that builds up in animal and human tissues and is exhaled out as a byproduct of respiration. Whereas, in the case of photoautotrophic organisms like plants and cyanobacteria, CO2 is a key reactant in photosynthesis. Carbon dioxide transport in circulation is considerably less complicated than oxygen transport.

Transport of CO2 in humans

Carbon dioxide transport in the blood circulation of humans has a tricky process. CO2 molecules are delivered in the blood from body tissues to the lungs through direct dissolution, haemoglobin binding, or bicarbonate ion transport. Several factors influence carbon dioxide’s transit in the blood. Carbon dioxide, for starters, is more soluble in blood than oxygen. About 5% to 7% of all carbon dioxide is dissolved in the plasma. 

On the other hand, carbon dioxide can connect to plasma proteins or enter red blood cells and bond to haemoglobin. About 10% of the carbon dioxide is transported in this form. A substance termed carbaminohemoglobin is generated when carbon dioxide binds to haemoglobin. Carbon dioxide binding to haemoglobin is reversible. As a result, when carbon dioxide enters the lungs, it can easily break from haemoglobin and be eliminated from the body.

Third, the bicarbonate buffer mechanism carries the vast bulk of carbon dioxide molecules (85%). Carbon dioxide diffuses into the red blood cells in this mechanism. Carbonic anhydrase (CA), a protein found in red blood cells, rapidly transforms carbon dioxide into carbonic acid (HCO3). Carbonic acid is an unstable intermediate molecule that instantly breaks down into bicarbonate and hydrogen (H+) ions. 

Since CO2 is rapidly converted to bicarbonate ions, this reaction allows carbon dioxide to be taken into the bloodstream at a lower concentration. The generation of H+ ions is also a byproduct of this process. Blood pH can be altered if too much H+ is generated. On the other hand, haemoglobin binds to free H+ ions, limiting pH changes. In exchange for a chloride ion (Cl–), the freshly-generated bicarbonate ion is transferred from the red blood cell to the blood’s liquid mixture. 

The bicarbonate ion is transferred back into the red blood cell in exchange for the chloride ion when the blood enters the lungs. The bicarbonate ion attaches to the H+ ion after it dissociates from haemoglobin. The carbonic acid intermediate is formed and transformed back to carbon dioxide by CA’s enzymatic action. During exhalation, the carbon dioxide created is evacuated through the lungs. 

Transport of CO2 in plants

Plants absorb carbon dioxide from the soil, water, and sunlight. CO2 is transported to and from all living cells through microscopic holes (pores) known as stomata on the surface of leaves and stems and a web of air spaces within the plant. To nourish themselves, plants use carbon dioxide in the photosynthesis process. The process begins with the help of sunlight and water once the carbon dioxide penetrates the plant. 

Diffusion through a damp membrane is the most basic process for gas exchanges in plants. Diffusion is the movement of molecules in the direction of the concentration gradient, from a region of higher concentration to a region of lower concentration. Molecules migrate through cellular membranes kept wet by fluid in living cells. 

Importance of transport of CO2

Plants, animals, and humans require material transportation because each cell requires a consistent supply of nutrients and oxygen to release energy through respiration. To be digested by the cells, the food we eat is broken down into smaller components. All of our body’s cells receive oxygen from the air we breathe. Our bodies also need to regularly get rid of waste products like carbon dioxide. Biological mechanisms can not work without CO2, and our bodies have a specialised transport system for transporting CO2. Plants, too, use a complicated transport system to move carbon dioxide.

Conclusion

Hence, CO2 transportation is highly significant for all life processes where a proper breakdown of the CO2 process helps in respiration and other biological functions. It has a role in maintaining the gaseous exchanges occurring in a living organism. Thus, the guard cells’ holes, known as stomata, are where carbon dioxide enters and oxygen leaves the plant. In animals, breathing gases are generally carried via simple diffusion. And diffusion of breathing gases occurs in humans at the capillary beds that separate blood from tissue fluid. Plants, animals, and humans require material transportation because each cell requires a consistent supply of nutrients and oxygen to release energy through respiration.