1. Transport of Gases in Blood
Oxygen Transport
Carbon Dioxide Transport
22-Nov-18
Transport of Gases

2. Dissolved O2 in Plasma At 37 0C and PO2 of 95 mmHg
Only 0.30 ml O2/ 100 ml of blood
Thus total quantity of O2 transported
Would be equal to 5000 * (0.3/100) = 15.0 ml O2/min
This amount is not sufficient for the metabolic processes
22-Nov-18
Transport of Gases

3. Transport of O2 Bound to Hb
Haemoglobin
Found in RBCs
Composed of 4 polypetide chains
Each containing a pigment (heme)
Of the total amount of O2 transported in blood, about
98.5% is bound to Hb
1.5% is dissolved in plasma
22-Nov-18
Transport of Gases

4. Binding of O2 to Hb After diffusing across the RM
O2 dissolves in plasma
Then into RBC
Where it combine reversibly with Hb
Converts deoxy-Hb into Oxy-Hb
Alveoli
PACO2 = 40
PAO2 = 100
CO2 O2 O2
CO2 O2 Hb
PvCO2 = 46 mm Hg
PaCO2 = 40 mm Hg
PvO2 = 40 mm Hg
PaO2 = 97 mm Hg
22-Nov-18
Transport of Gases

5. Binding of O2 to Hb HB + 4(O2) ⇆ Hb(O2)4
Reactive sites are the 4 Fe++ atoms
One mole of Hb is capable of combining with 4 moles of O2
Alveoli
PACO2 = 40
PAO2 = 100
CO2 O2 O2
CO2 O2 Hb
PvCO2 = 46 mm Hg
PaCO2 = 40 mm Hg
PvO2 = 40 mm Hg
PaO2 = 97 mm Hg
22-Nov-18
Transport of Gases

6. Binding of O2 to Hb Under ideal conditions In the normal human body
1 gm of Hb
Combine with 1.39 ml O2
In the normal human body
1 gm of Hb combine with 1.34 to 1.36 ml of O2 (Huffner’s number)
Small fraction of Hb is in an inactive form
22-Nov-18
Transport of Gases

7. Binding of O2 to Hb When the Fe++ is oxidized to Fe+++ Carbon monoxide
The haemoglobin is known as
Methaemoglobin
Its ability to combine with O2 is lost
Carbon monoxide
Combine with Fe++
Displaces the O2 from it
22-Nov-18
Transport of Gases

8. Binding of O2 to Hb Cyanide combine and inactivate Hb
It combines with Fe+++ of the methaemoglobin
Hb (Fe++) ⇆ Hb (Fe+++) + CN  Cyano –methaemoglobin
Normally methaemoglobin is <1%
Cyano-methaemoglobin
Is stable
Reaction is one way
22-Nov-18
Transport of Gases

9. Binding of O2 to Hb Other respiratory pigments include Myoglobin
Has one Fe++ atom
Functions as for 1 atom of Fe++ in Hb
Cytochrome
Change from O2 poor to O2 rich
Associated with oxidation of Fe++ to Fe+++
22-Nov-18
Transport of Gases

10. Oxygen Capacity of Blood
Maximum amount of O2 that can be bound by the Hb
1 gm of Hb combine with 1.34 ml O2
Amount of Hb available = 15 gm Hb/100 ml of blood
15*1.34 = 20.1 ml O2 / 100 ml blood
This is the O2 carrying capacity of blood
22-Nov-18
Transport of Gases

11. Oxygen Flux Total amount of O2 transported by blood per minute
O2 flux = C.O*(arterial O2 content) = 5000*(20/100) = 1000 ml O2 /min
Under normal condition
250 ml of O2 is utilized (25% of O2 flux)
Thus circulating blood loses 25% of its Oxygen
Venous blood is approx 75% saturated with O2
The 75% of the un-extracted O2 forms “reserve”
22-Nov-18
Transport of Gases

12. Oxygen Flux Determined by Cardiac output Hb concentration
Saturation with O2
22-Nov-18
Transport of Gases

13. O2-Hb Dissociation (Association) Curve
The property of Hb
Ability to change from deoxy-Hb to Oxy-Hb at extremely rapid rate at PO2 in lungs
Hb + O2 ⇌ Hb(O2)
The ability to give up O2 in tissue
Hb(O2) ⇌ Hb + O2
This ability varies & depends on
Metabolic activities & requirements
22-Nov-18
Transport of Gases

14. O2-Hb Dissociation (Association) Curve
The effective release of O2 at tissue capillaries occurs because
Amount of O2 combined to Hb varies with
Po2
Acidity
Temperature
22-Nov-18
Transport of Gases

15. O2-Hb Dissociation (Association) Curve
The relationship between the
PO2 & Degree of Hb oxygenation
Is known as O2 – Hb dissociation (association) curve
The proportion of HbO2 to the total Hb of blood
Give % saturation of Hb
100
Loading zone 80
Hb saturation (%) 60 50
Unloading zone 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

16. O2-Hb Dissociation (Association) Curve
% Saturation of Hb is given by
(HbO2/Hb)*100
(O2 content /capacity) * 100
Curve is sigmoid shaped
Steep slope between PO2 10 to 60 mm Hg
Flat portion between PO2 70 to 100 mm Hg
100
Loading zone 80
Hb saturation (%) 60 50
Unloading zone 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

17. O2-Hb Dissociation (Association) Curve
The extent to which Hb combine with O2
Increase very rapidly from 10 to 60 mm Hg
At PO2 60 mm Hg
90% of Hb is combined with O2
Above PO2 60 mm Hg
Further increase in PO2
Produces only a small increase in HbO2
100
Loading zone 80
Hb saturation (%) 60 50
Unloading zone 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

18. PO2 Vs Quantity of O2 Bound to Hb
97% sat ; 19.4 ml O2
Normal arterial blood
97% saturated Hb
Has 19.4 ml O2 / 100 ml blood
At the tissue level
PO2 is 40 mm Hg
Hb sat is 75%
Blood has 14.4 ml O2 /100 ml blood 20
5 mls
Loading zone 16
75% sat, 14.4 ml O2 12
O2 content ( ml O2/100 ml blood) [V%]
Unloading zone 8 4 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

19. PO2 Vs Quantity of O2 Bound to Hb
97% sat ; 19.4 ml O2
Thus under normal conditions
About 5 ml O2/100 ml blood are transported from lungs to tissue 20
5 mls
Loading zone 16
75% sat, 14.4 ml O2 12
O2 content ( ml O2/100 ml blood) [V%]
Unloading zone 8 4 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

20. PO2 Vs Quantity of O2 Bound to Hb
97% sat ; 19.4 ml O2
During exercise
Tissue PO2 can fall to 15 mm Hg
At this pressure only about 4.4 ml O2 remain bound to Hb/ 100 ml blood
Thus 15 ml O2 / 100 ml blood
Delivered to tissues (3 times normal) 20
5 mls
Loading zone 16
75% sat, 14.4 ml O2 12
O2 content ( ml O2/100 ml blood) [V%]
Unloading zone 8 4 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

21. Factors Affecting O2-Hb Dissociation curve
Influence of acidity & CO2
Bohr effect
Changes in pH
Alters the affinity of Hb for O2
An increase in H+ conc shift the curve to the right
Decrease in affinity of Hb for O2
100
pH 7.6 80
pH 7.4
pH 7.2
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

22. Factors Affecting O2-Hb Dissociation curve
Influence of acidity & CO2
Bohr effect
Co2 combines with
The  - amino gps of Hb
This lowers the affinity of Hb for O2
100
pH 7.6 80
pH 7.4
pH 7.2
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

23. Factors Affecting O2-Hb Dissociation curve
Changes in pH
Alters the affinity of Hb for O2
An increase in H+ conc shift the curve to the right
There is an increase in P50
Lowers the affinity of Hb for O2
100
pH 7.6 80
pH 7.4
pH 7.2
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

24. Factors Affecting O2-Hb Dissociation curve
5 ml O2 /100 ml blood
When the curve is shifted to the right
Decreased affinity of Hb for O2
Any fall in PO2 releases more O2 to the tissues
100
pH 7.6 80
pH 7.4
> 5 ml O2 released
pH 7.2
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

25. Factors Affecting O2-Hb Dissociation curve
< 5 ml O2
A decrease in H+ conc shift the curve to the left
There is a decrease in P50
Increase affinity of Hb for O2
Normally
About 5 ml O2 released at the tissue
When curve is shifted to left
Less the 5 ml O2 / 100 ml blood is released
100
pH 7.6
5 ml O2 80
pH 7.4
pH 7.2
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

26. Factors Affecting O2-Hb Dissociation Curve
5 ml O2 /100 ml blood
At tissue level a fall in pH
Facilitates O2 dissociation from Hb
At the lung level
The increase in ph facilitates
Combination of O2 with deoxy - Hb
100
pH 7.6 80
pH 7.4
> 5 ml O2 released
pH 7.2
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

27. Influence of temperature
A rise in temperature
Shift the curve to the right
Decrease affinity of Hb for O2
Favours off loading of O2 to the tissues
The opposite is true when temperature decreases
100
10OC
20OC 80
37OC
43OC
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

28. Influence of 2:3 Diphospoglycerate
Affinity of Hb for O2 is affected by organic phosphates
2:3 DPG is plentiful in RBC
End product of glycolysis via E-M pathways
Binds to  chain of deoxy-Hb
100
2:3 DPG 80
2:3 DPG
2:3 DPG
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

29. Influence of 2:3 Diphospoglycerate
1 mol of deoxy-Hb binds to 1 mol of 2:3 DPG
HbO2 + 2:3 DPG ⇌ Hb – 2:3 DPG + O2
An increase in 2,3DPG shift the reaction to right
Causing more O2 to be liberated
100
2:3 DPG 80
2:3 DPG
2:3 DPG
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

30. Influence of 2:3 Diphospoglycerate
Factors affecting 2,3 DPG conc in RBC
Acidosis inhibit glycolysis
2,3 DPG levels falls
Hormones
Thyroid, GH, androgens
Increase 2,3 DPG
100
2:3 DPG 80
2:3 DPG
2:3 DPG
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

31. Influence of 2:3 diphospoglycerate
Ascent to high altitudes
Increase 2,3 DPG
Anaemia
100
2:3 DPG 80
2:3 DPG
2:3 DPG
Hb saturation (%) 60 50 40 20 20 40 60 80
100 27
PO2 (mm Hg)
P50
22-Nov-18
Transport of Gases

32. Transport of CO2
22-Nov-18
Transport of Gases

33. CO2 Transport
CO2 is produce in the cells as end product of oxidative metabolism
Diffuses from the cells into
Interstitial fluid
Plasma where it
Raises the PCO2 of capillary and venous blood
22-Nov-18
Transport of Gases

34. CO2 Transport CO2 is transported in three forms
Physically dissolved in plasma (10%)
As bicarbonate ions in plasma (60%)
As carbamino compounds (30%)
22-Nov-18
Transport of Gases

35. CO2 Transport in Plasma Physically dissolved depend on the
Partial pressure
Solubility coefficient
Hydration of CO2
CO2+ H2O ⇌ H2CO3 ⇌ H+ + HCO3-
In plasma there is no carbonic anhydrase
Equilibrium is far to the left
Accumulation of H2CO3 stops the reaction
H+ are buffered by plasma buffers
22-Nov-18
Transport of Gases

36. CO2 Transport in Plasma Formation of carbamino compounds
Amino groups have ability to combine with CO2
To form carbamino compounds
R-N(H2) + CO2 ⇌ R-NH-COO- + H+
This reaction restricted to terminal AA or
Side chains AA (lysine, arginine)
22-Nov-18
Transport of Gases

37. CO2 Transport by RBC Small amount of CO2 dissolved in fluid in RBC
Hydration of CO2
CO2+ H2O ⇌ H2CO3 ⇌ H+ + HCO3-
In RBC reaction proceed to right because
Presence of carbonic anhydrase
H+ and HCO3- do not accumulate
22-Nov-18
Transport of Gases

38. CO2 Transport by RBC H+ cannot readily move out of RBC
It is buffered by Hb buffer
H+ + HbO2 ⇌ H+.Hb + O2
As H+ binds to Hb
Reduces Hb affinity for O2
Cause unloading of O2 to tissues
Cl-
HCO3-
CO2
Cl- CA
CO2 + H2O2⇌ H2CO3⇌ H+ + HCO3-
H++ HbO2
HHb + CO2
HHb + O2
Carbamino-Hb O2
22-Nov-18
Transport of Gases

39. CO2 Transport by RBC Presence of deoxy-Hb in blood
Increase ability to carry CO2 from the tissues
Oxygenation in pulmonary capillaries
Increase Hb ability to unload CO2
This is the Haldane effect
Cl-
HCO3-
CO2
Cl- CA
CO2 + H2O2⇌ H2CO3⇌ H+ + HCO3-
H++ HbO2
HHb + CO2
HHb + O2
Carbamino-Hb O2
22-Nov-18
Transport of Gases

40. CO2 Transport by RBC HCO3- leaves the RBC Concentration gradient
Chloride shift
Chloride/bicarbonate carrier protein
Cl- move into RBC
HCO3- move into plasma
Cl-
HCO3-
CO2
Cl- CA
CO2 + H2O2⇌ H2CO3⇌ H+ + HCO3-
H++ HbO2
HHb + CO2
HHb + O2
Carbamino-Hb O2
22-Nov-18
Transport of Gases

41. CO2 Transport by RBC In the pulmonary capillaries
Opposite movement of Cl- shift occurs
Cl- move into plasma
HCO3- move into RBC
Cl-
HCO3-
CO2
Cl- CA
CO2 + H2O2⇌ H2CO3⇌ H+ + HCO3-
H++ HbO2
HHb + CO2
HHb + O2
Carbamino-Hb O2
22-Nov-18
Transport of Gases

42. CO2 Transport by RBC CO2 can also combine with amino-terminals of Hb
CO2 + HbNH2 ⇌ HbCOOH
Carbamino-haemoglobin
Cl-
HCO3-
CO2
Cl- CA
CO2 + H2O2⇌ H2CO3⇌ H+ + HCO3-
H++ HbO2
HHb + CO2
HHb + O2
Carbamino-Hb O2
22-Nov-18
Transport of Gases

43. CO2 Transport Although the major reactions regarding transport of CO2
Occur in the RBCs
The bulk of CO2 is transported in plasma
In the form of HCO3-
22-Nov-18
Transport of Gases

44. CO2 Dissociation Curve CO2 can exist in blood in many forms
Normal operating range
CO2 can exist in blood in many forms
As free CO2
In chemical combination with
H2O Hb
Plasma proteins
Total quantity of CO2in all these forms in blood depend on PCO2 60 40
CO2 in blood (vol%) 20 10 20 30 40 50 60
PCO2 mm Hg
22-Nov-18
Transport of Gases

45. CO2 Dissociation Curve
Normal operating range
The relationship of the total CO2 in all these forms vs PCO2 is known as
The CO2 dissociation curve
The curve is nearly straight line with no plateau or steep region 60 40
CO2 in blood (vol%) 20 10 20 30 40 50 60
PCO2 mm Hg
22-Nov-18
Transport of Gases

46. CO2 Dissociation Curve The normal PCO2 range is
Normal operating range
The normal PCO2 range is
40 mm Hg in arterial blood
45 mm Hg in venous blood
Normal concentration of CO2 in all its forms is 50 volumes% 60 40
CO2 in blood (vol%) 20 10 20 30 40 50 60
PCO2 mm Hg
22-Nov-18
Transport of Gases

47. The Haldane Effect Presence of O2 As blood passes through the tissues
Normal operating range
Presence of O2
Shift the curve to the right
As blood passes through the tissues
Point A
PO2 = 40 mm Hg
Normal PCO2 = 45 mm Hg
Concentration rises to 52 volumes% 55
PO2 = 40 A 50
CO2 in blood (vol%)
PO2 = 100 B 45 35 40 45 50
PCO2 mm Hg
22-Nov-18
Transport of Gases

48. The Haldane Effect In the lungs (Point B)
Normal operating range
In the lungs (Point B)
PO2 = 100 mm Hg
PCO2 = 40 mm Hg
Conc falls to 48 vol%
During transport of CO2 from tissue to lungs
Only 4 volume% of CO2 is exchanged 55
PO2 = 40 A 52 50
CO2 in blood (vol%)
PO2 = 100 48 B 45 35 40 45 50
PCO2 mm Hg
22-Nov-18
Transport of Gases