Transport of Oxygen and Carbon Dioxide | O2 Hemoglobin Dissociation Curve Physiology
Another addition in respiratory physiology is here. Transport of Oxygen and Carbon Dioxide.
I will assume here, that you have our previous videos from the respiratory series including Introduction to Respiratory System, Lung Mechanics, and Exchange of Gases and Gas Laws. So that, you can have a better understanding.
▬ 🕘 Timestamps
00:00 - O2 Hemoglobin Dissociation Curve Physiology
05:36 - Hemoglobin Dissociation Curve shift to Left and Right
07:35 - Right Shift of O2 Hemoglobin Dissociation Curve
15:56 - Left Shift of O2 Hemoglobin Dissociation Curve
17:22 - Fetal Hemoglobin (HbF)
18:38 - Cabon Monoxide Poisoning
21:15 - Link to video lectures on sqadia.com
▬ 📌 Transport of Oxygen and Carbon Dioxide
The process of carrying gases from the alveoli to the tissues and back is known as gas transport. Blood serves to transport respiratory gases. Oxygen, which is essential for the cells, is transported from the alveoli of the lungs to the cells.
While Carbon dioxide is the waste product in cells. So, it is transported from cells to the lungs.
The transport of oxygen from the lungs is carried in blood in two forms.
🔵 1.5% is in the Dissolved form in blood plasma.
🔵 The remaining 98.5 % of oxygen is bound to Haemoglobin in the RBCs.
While transport of Carbon Dioxide to the lungs is carried in blood in four forms.
🟠 About 7% is in the Dissolved form in blood plasma.
🟠 A negligible amount is in the form of carbonic acid.
🟠 About 63% is present as bicarbonates.
🟠 And, about 30% is transported as carbamino compounds.
▬ 📌 Transport of Oxygen
Oxygen binds to the iron portion of hemoglobin, forming oxyhemoglobin. This is called loading, or oxygenation. Oxyhemoglobin travels through the circulatory system to tissue cells.
Once there, the difference in pH between the arterial and venous blood is enough to break the bond between the oxygen and the hemoglobin. Causing, the release of O2 to the tissues. This is called unloading, or deoxygenation.
Now, It’s important to realize that, although each hemoglobin molecule has the capacity to unite with up to four molecules of oxygen, this isn’t always the case.
The number of oxygen molecules hemoglobin takes up, is referred to as oxygen saturation. Saturation varies, depending on the partial pressure of oxygen.
A graph showing the relationship between the partial pressure of oxygen and oxygen saturation is known as the oxyhemoglobin dissociation curve.
Certain factors, cause it to shift either to the right or to the left.
The oxygen hemoglobin dissociation curve shifted to the right indicating unloading. It occurs when:
🟢 the affinity of hemoglobin for O2 is decreased,
🟢 or, when the P50 is increased,
🟢 when pO2 is low.
Decreased blood pH resulting from increased carbon dioxide concentration in the blood, causes a decrease in the oxygen affinity of hemoglobin. Hence, resulting in unloading. This is known as Bohr’s effect, and it causes a left shift to the curve.
The oxygen hemoglobin dissociation curve shifted to the left indicating loading. It occurs when:
⚫️ when, the affinity of hemoglobin for O2, is increased,
⚫️ Or when the P50 is decreased,
⚫️ Or where there is high pO2 in the blood.
You can learn about them in detail in the video.
▬ 📌 Transport of Carbon Dioxide
Hemoglobin can transport both O2 and CO2, at the same time. This is because they bind to different sites on the hemoglobin molecule. CO2 combines with hemoglobin to form carbamino hemoglobin or Carbhemoglobin.
Also, carbon dioxide in RBCs undergoes hydration, in the presence of carbonic anhydrase enzyme. Resulting in the formation of highly unstable carbonic acid. That readily dissociates into bicarbonate and hydrogen ions. Now, negatively charged bicarbonate ions, move out of RBC into the plasma.
In exchange, chloride ions move into the RBC. This exchange of a chloride ion for a bicarbonate ion across the RBC membrane is known as the Chloride Shift or Hamburger Phenomenon.
Reverse happens in the lungs, known as Reverse Chloride Shift.
Now, the Carbon dioxide dissociation curve is the curve that demonstrates the relationship between the partial pressure of carbon dioxide, and the quantity of carbon dioxide that combines with blood.
Binding of O2 with hemoglobin tends to displace CO2 from the blood, known as CO2 unloading.
This effect is known as the Haldane effect.
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