Carbon dioxide (CO2) is the significant waste product the aerobic respiration. Too much or too little CO2 in the blood deserve to lead to severe consequences. This short article will consider CO2 transport in the blood, its function in preserving blood pH and conclude by mentioning its clinical relevance.

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Carbon Dioxide in the Blood

The main function of CO2 is to manage the pH of the blood – this is much more important that delivering CO2 come the lungs for exhalation.


Fig 1 – The reaction the produces bicarbonate in ~ the body.

Figure 1 shows how CO2 disappear in the blood. The counter of carbonic acid (H2CO3) come a hydrogen and also bicarbonate ion (H+ + HCO3–) is nearly instantaneous. A little amount of liquified CO2 produce a little rise in hydrogen ion which is qualified of transforming the blood pH. The proportion of CO2 to HCO3– is an essential and defines why this occurs.

This ratio is around 1:20, thus a increase of 1 CO2 requires a matching rise the 20 HCO3– to prevent alterations to blood pH through buffering the boost in acidity. As thorough in the reaction over only 1 HCO3–, is created from every CO2 as such the blood pH will become much more acidic as result of the overfill hydrogen ions. There must as such be one alternate technique of transportation to stop severe acidosis every time we respire and create CO2.

Methods of Transport

CO2 is transported in the blood in 3 ways; as a hydrogen lead carbonate (HCO3–), together carbamino compounds and as dissolved CO2­.

Carbamino Compounds

About 30% of all CO2 is transported together carbamino compounds. At high concentration carbon dioxide straight binds come amino acids and the amine groups of haemoglobin to create carbaminohaemoglobin. Carbamino formation is most efficient at the periphery where CO2 production is high as result of cellular respiration.

The Haldane effect also contributes come the formation of carbamino compounds. This occurs wherein O2 concentration is lower (as in the active peripheries whereby O2 is gift consumed) hence the CO2 transferring capacity of the blood is increased. This is because release of O2 from Hb disclosure binding that CO2.

Formation of carbamino compounds achieves 2 goals:

Stabilising pH – CO2 is unable to leaving the blood cabinet to add to transforms in pHBohr impact – the stabilises the T state of haemoglobin, promoting the relax of O2 from the various other subunits of haemoglobin right into the tissues that are most active, undergoing the many respiration and also producing the most CO2

When the blood cell reaches locations of high O2 concentrations again (such together the lungs), it preferentially binding O2 again. This stabilises the R state, cultivating the relax of CO2 (Haldane effect) allowing much more O2 come be picked up and also transported in the blood.

HCO3– ions

60% of all CO2 is transported through manufacturing of HCO3– ions in the red blood cell. This is described in the diagram below (Figure 2). CO2 diffuses right into the red blood cells and is convert to H+ and HCO3– by an enzyme called carbonic anhydrase. This HCO3– is transported earlier into the blood via a chloride-bicarbonate exchanger (aka anion exchanger/AE). The HCO3– have the right to now act as a buffer versus any hydrogen in the blood plasma.

The H+ created by the carbonic anhydrase reaction in the red blood cell binds to haemoglobin to create deoxyhaemoglobin. This contributes to the Bohr effect as O2 release from haemoglobin is advocated in active tissues wherein H+ concentration is higher. It additionally prevents hydrogen start the blood to lower pH, stabilising the pH.

When the red blood cell reach the lungs, oxygen binding to the haemoglobin and also promotes the R state, enabling the relax of H+ ions. These hydrogen ions become cost-free to react with bicarbonate ions to produce CO2 ­and H2O, wherein the CO2 is exhaled. Hence the high O2 concentrations minimize the CO2 transferring capacity the blood, in accordance with the Haldane effect.


Fig 2 – chart showing techniques of carrying carbon dioxide in the blood. The reaction creating bicarbonate is presented within the red blood cell.

Dissolved in Plasma

About 10% of every CO2 is transported dissolved in plasma. The lot of gas liquified in a liquid relies on the solubility and also the partial pressure of the gas. CO2 is an extremely soluble in water (23x much more soluble than O2) and the partial push of inspired CO2 is ~40mmHg. Regardless of its solubility, just a minority the the complete CO2 in blood is actually transported dissolved in plasma.

The partial pressure, however, is greater in the perimeter where tissues are developing CO2 and lower at the alveoli whereby CO2 is being released. This allows more CO2 to be dissolved in the periphery while that is released into the gas phase at the alveoli whereby the partial pressures room lower.

Clinical relationship – Metabolic Acidosis

Acidosis occurs when the pH the the blood falls below 7.35 and can be broadly classified right into metabolic and also respiratory acidosis.

Metabolic acidosis can an outcome from one excess of H+ manufacturing or a reduction in the HCO3– buffer. Problem such together diabetic ketoacidosis have the right to increase mountain production, when a disorder the the kidneys themselves such as in chronic kidney an illness may minimize HCO3– production.

In together cases, the respiratory device attempts come compensate by enhancing respiration price (hyperventilating). This allows one to “blow off” part CO2 to reduce the acidity of the blood. However, the main correction need to be completed by the kidney which have the right to both boost hydrogen excretion to reduce the mountain of the blood and increase bicarbonate reabsorption to enable increased buffering that blood acidity.

Symptoms the acidosis encompass rapid breathing (to punch off CO2), confusion, fatigue and also headache.

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that is crucial to recognize it as it can be mistaken for intoxication.