Carbon Dioxide Transport in the Blood (Nursing)

by Jasmine Clark

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    00:01 So now let's switch and talk about what happens with carbon dioxide transport.

    00:08 So when carbon dioxide transport, it is transported in three different ways.

    00:13 First it can be dissolved in plasma.

    00:17 Also, like oxygen, carbon dioxide can also bind to the hemoglobin molecule.

    00:24 Instead of binding to the heme, however, the carbon dioxide binds to the globin part when carbon dioxide is bound to hemoglobin.

    00:34 It is referred to as carb amino hemoglobin.

    00:39 The remainder of our carbon dioxide molecules, however, are transported by way of bicarbonate ions in our plasma.

    00:49 These bicarbonate ions are formed by carbon dioxide combining with water to form a molecule known as carbonic acid.

    00:59 This carbonic acid can then be dissociated into bicarbonate and H+.

    01:08 So we see this chemical formula here.

    01:11 Remember carbon dioxide plus water gives you carbonic acid the carbonic acid can then dissociate into hydrogen and bicarbonate ions.

    01:22 So this is a reversible process that can occur either in the blood plasma, but can also occur in our red blood cells.

    01:32 The red blood cells is where this occurs more often and the reason why is because our red blood cells have an enzyme known as carbonic anhydrase.

    01:44 So in our systemic capillaries, the bicarbonate can be created and then diffuse from these red blood cells into the plasma.

    01:55 The out rush of bicarbonate ions is going to be balanced by an influx or a moving in of chloride ions so that we maintain the negative charged in the cells.

    02:09 This movement of chloride as the bicarbonate moves out and the chloride moves in is referred to as our chloride shift.

    02:21 So now let's look at this in an image.

    02:23 So recall there are three different ways that we're going to transport our carbon dioxide.

    02:29 We can transport carbon dioxide directly by dissolving it in our plasma.

    02:34 We can also transport carbon dioxide by binding it to water to form carbonic acid and then dissociating it into bicarbonate and H+ thus transporting the carbon dioxide by way of bicarbonate ions, and then the third way is by the carbon dioxide binding to hemoglobin in order to form carbamino-hemoglobin.

    03:02 So this process is going to be reversed and our pulmonary capillaries compared to what happens in our tissues.

    03:10 So whereas in the tissues the bicarbonate ions were moving out of the red blood cells and this case the bicarbonate ions are going to move into the red blood cells.

    03:22 Subsequently, the chloride ions are going to shift in the opposite direction and move out back into the plasma.

    03:31 The bicarbonate ions are now going to bind to H+ in order to form carbonic acid.

    03:40 The carbonic acid is then going to be split by a carbonic anhydrase into carbon dioxide and water.

    03:49 And now the carbon dioxide is going to diffuse into the alveoli and eventually be exhaled.

    03:57 So if you recall the chemical reaction, this is the reverse of the chemical reaction where now we are starting with bicarbonate in H+ going through Carbonic anhydrase and moving back into, carbon dioxide and water.

    04:18 So we can see this depicted here.

    04:21 So again, the carbon dioxide can either diffuse directly out of the plasma which happens less often or we can do the reverse of the reaction we saw in the tissues and our bicarbonate is going to be converted into carbon dioxide and water or we can also get unloading of carbon dioxide from the carbamino-hemoglobin.

    04:47 So the amount of carbon dioxide that is transported is going to be affected by the partial pressure of oxygen.

    04:56 The lower the partial pressure of oxygen and the hemoglobin saturation of oxygen the more that carbon dioxide can be carried on these hemoglobin molecules.

    05:08 When we reduce hemoglobin, this is going to buffer the H+ ions and we are able to now form the carbamino-hemoglobin more easily.

    05:19 So reduced hemoglobin that does not contain oxygen molecules are able to better bind to carbon dioxide in order to form carbamino-hemoglobins.

    05:34 So this process is going to encourage the carbon dioxide exchange at both the tissues and at the lungs.

    05:42 So at the tissues, as more carbon dioxide enters the blood there's going to be more oxygen that's going to dissociate from hemoglobin.

    05:51 We already talked about this as the Bohr effect.

    05:55 However as the hemoglobin releases, the oxygen and becomes reduced it is now more readily able to bind to the carbon dioxide to form carbamino-hemoglobin.

    06:09 This is what we refer to as to Haldane effect.

    06:13 So carbon dioxide actually plays an important role in our Bloods pH levels.

    06:21 So if the H+ concentration and our blood rises, or the blood becomes more acidic, we are going to remove this H+ by combining it with bicarbonate to form carbonic acid and then eventually forming carbon dioxide and water.

    06:40 However, if the H+ concentrations begin to drop then we're going to actually start to dissociate our carbonic acid into H+ and bicarbonate.

    06:54 The interesting thing about this is that if you go back to that chemical reaction, this is referred to as Le chatelier's principle where the increase on one side of an equilibrium reaction drives the reaction and the opposite direction and vice versa.

    07:13 So because of this our bicarbonate is going to be considered our alkaline reserves and what we refer to as the carbonic acid bicarbonate buffer system.

    07:25 So when rh+ gets too high we are able to buffer it with bicarbonate ions.

    07:33 Changes in our respiratory rate in depth, are going to be able to affect our blood pH as well.

    07:40 So when we do slow shallow breathing this causes an increase in the concentration or partial pressure of carbon dioxide in our blood.

    07:51 This is going to shift that carbonic acid reaction toward the production of H+ and bicarbonate and therefore is going to result in a drop in our pH.

    08:06 Opposite to this, if we undergo rapid deep breathing we're going to be releasing more carbon dioxide than our body should and this can result in a rise in our pH.

    08:20 Changes in ventilation can help adjust the pH when the disturbances are caused by metabolic factors.

    08:27 So for example, if you have something going on in your body that is causing your blood pH to go up or down our body can adjust to this by changing our breathing in order to adjust the ph and this is a very quick reaction.

    About the Lecture

    The lecture Carbon Dioxide Transport in the Blood (Nursing) by Jasmine Clark is from the course Respiratory System – Physiology (Nursing).

    Included Quiz Questions

    1. Helps the blood resist changes in pH
    2. Helps the blood stimulate changes in pH
    3. Helps the blood resist changes in glucose levels
    4. Helps the blood stimulate changes in glucose levels

    Author of lecture Carbon Dioxide Transport in the Blood (Nursing)

     Jasmine Clark

    Jasmine Clark

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