1. Faisal I. Mohammed, MD, PhD
Respiratory system L4
Faisal I. Mohammed, MD, PhD
University of Jordan

2. Transport of Oxygen and Carbon Dioxide
Oxygen transport
Only about 1.5% dissolved in plasma
98.5% bound to hemoglobin in red blood cells
Heme portion of hemoglobin contains 4 iron atoms – each can bind one O2 molecule
Oxyhemoglobin
Only dissolved portion can diffuse out of blood into cells
Oxygen must be able to bind and dissociate from heme
University of Jordan

3. OXYGEN IN THE BLOOD in Milliliters: 200 ml in 1litre arterial blood.
Transport of O2 and CO2
Oxygen in blood:
Blood of a normal person contains about 15 gm of Hb in each 100 ml of blood.
Each gram of Hb can bind with a maximum of 1.34 ml of O2
- 6
OXYGEN IN THE BLOOD in Milliliters: 200 ml in 1litre arterial blood.

5. Relationship between Hemoglobin and Oxygen Partial Pressure
Higher the PO2, More O2 combines with Hb
Fully saturated – completely converted to oxyhemoglobin
Percent saturation expresses average saturation of hemoglobin with oxygen
Oxygen-hemoglobin dissociation curve
In pulmonary capillaries, O2 loads onto Hb
In tissues, O2 is not held and unloaded
75% may still remain in deoxygenated blood (reserve)
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6. Hemoglobin and Oxygen
Other factors affecting affinity of Hemoglobin for oxygen
Each makes sense if you keep in mind that metabolically active tissues need O2, and produce acids, CO2, and heat as wastes
Acidity (pH)
PCO2
Temperature
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7. Hemoglobin and 02 Transport
280 million hemoglobin/RBC.
Each hemoglobin has 4 polypeptide chains and 4 hemes.
In the center of each heme group is 1 atom of iron that can combine with 1 molecule 02.
Insert fig

8. Hemoglobin
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9. How does Hemoglobin carry Oxygen?
Hemoglobin exists in two forms:
Oxyhemoglobin: HbO2
O2 + Hb HbO2
Iron in Hb binds to O2
4 O2 molecules per Hb molecule
Deoxyhemoglobin
The fraction of all the Hemoglobin in the form of Oxyhemoglobin is expressed as Hemoglobin saturation.

10. Hemoglobin (continued)
Methemoglobin:
Has iron in the oxidized form (Fe3+).
Lacks electrons and cannot bind with 02.
Blood normally contains a small amount.
Carboxyhemoglobin:
The reduced heme is combined with carbon monoxide.
The bond with carbon monoxide is 210 times stronger than the bond with oxygen.
Transport of 02 to tissues is impaired.

11. Hemoglobin (continued)
Oxygen-carrying capacity of blood determined by its [hemoglobin].
Anemia:
[Hemoglobin] below normal.
Polycythemia:
[Hemoglobin] above normal.
Hemoglobin production controlled by erythropoietin.
Production stimulated by PC02 delivery to kidneys.
Loading/unloading depends:
P02 of environment.
Affinity between hemoglobin and 02.

12. Oxyhemoglobin Dissociation Curve
Graphic illustration of the % oxyhemoglobin saturation at different values of P02.
Loading and unloading of 02.
Steep portion of the sigmoidal curve, small changes in P02 produce large differences in % saturation (unload more 02).
Decreased pH, increased temperature, and increased 2,3 DPG:
Affinity of hemoglobin for 02 decreases.
Greater unloading of 02:
Shift to the curve to the right.

13. Oxygen-hemoglobin Dissociation Curve
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14. Oxyhemoglobin Dissociation Curve
Insert fig.16.34

15. Effects of pH and Temperature
The loading and unloading of O2 influenced by the affinity of hemoglobin for 02.
Affinity is decreased when pH is decreased.
Increased temperature and 2,3-DPG:
Shift the curve to the right.
Insert fig

16. Effect of 2,3 DPG on 02 Transport
Anemia:
RBCs total blood [hemoglobin] falls, each RBC produces greater amount of 2,3 DPG.
Since RBCs lack both nuclei and mitochondria, produce ATP through anaerobic metabolism.
Fetal hemoglobin (hemoglobin f):
Has 2 -chains in place of the -chains.
Hemoglobin f cannot bind to 2,3 DPG.
Has a higher affinity for 02.

17. Inherited Defects in Hemoglobin Structure and Function
Sickle-cell anemia:
Hemoglobin S differs in that valine is substituted for glutamic acid on position 6 of the b chains.
Cross links form a “paracrystalline gel” within the RBCs.
Makes the RBCs less flexible and more fragile.
Thalassemia:
Decreased synthesis of a or b chains, increased synthesis of g chains.

18. Muscle Myoglobin Red pigment found exclusively in striated muscle.
Slow-twitch skeletal fibers and cardiac muscle cells are rich in myoglobin.
Have a higher affinity for 02 than hemoglobin.
May act as a “go-between” in the transfer of 02 from blood to the mitochondria within muscle cells.
Insert fig
May also have an 02 storage function in cardiac muscles.

19. Bohr Effect
As acidity increases (pH decreases), affinity of Hb for O2 decreases
Increasing acidity enhances unloading
Shifts curve to right
PCO2
Also shifts curve to right
As PCO2 rises, Hb unloads oxygen more easily
Low blood pH can result from high PCO2
University of Jordan

20. Temperature Changes
Within limits, as temperature increases, more oxygen is released from Hb
During hypothermia, more oxygen remains bound
2,3-bisphosphoglycerate
BPG formed by red blood cells during glycolysis
Helps unload oxygen by binding with Hb
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21. Fetal and Maternal Hemoglobin
Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin
Hb-F can carry up to 30% more oxygen
Maternal blood’s oxygen readily transferred to fetal blood
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22. Carbon dioxide in blood
CO2 produced by cells is carried by the blood in three forms
In physical solution Plasma/Erythrocyte: 7%
As Carbamino-Hemoglobin : 23%
CO2 + Hb  HbCO2
As Bicarbonate ions: 70%
Mostly in the Erythrocyte which has the enzyme, Carbonic anhydrase (Catalyses the formation of Carbonic acid 5000 times.)
CO2 + H2O  H2 CO3 [H+] + [HCO3-]

23. Carbon dioxide in blood
transported from the body cells back to the lungs (Tidal Co2) as:

24. CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3- Chloride shift
HCO3- accumulates inside RBCs as they pick up carbon dioxide
Some diffuses out into plasma
To balance the loss of negative ions, chloride (Cl-) moves into RBCs from plasma
Reverse happens in lungs – Cl- moves out as moves back into RBCs
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25. University of Jordan

26. Thank You
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