Detailed description about transport of gases and their exchange. It also includes Hb oxygen dissociation curve with special mention of bohr effect.

2. Prepared by:Majid ali bhat
T r a n s p o r t a n d e x c h a n g e
o f g a s e s
Presented to:Dr Sheeba

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CONTENT
Transporatation of C02
Transportation of 02
Exchange of gases
Hb-02 dissociation curve
Summary

4. The exchange of oxygen and carbon dioxide between alveolar air
and pulmonary blood occurs via passive diffusion, which is governed by the
behavior of gases as described by two gas laws, Dalton’s
law and Henry’s law.
Exchange of gases
Dalton’s law: each gas in a mixture of gases exerts its
own pressure as if no other gases were present. The pressure of a specific gas
in a mixture is called its partial pressure
These partial pressures determine the movement of O2 and CO2
between the atmosphere and lungs, between the lungs and blood,and
between the blood and body cells.

5. Exchange of gases
Henry’s law states that the quantity of a gas that will dissolve
in a liquid is proportional to the partial pressure of the gas and its
solubility.
In comparison to oxygen, much more CO2 is dissolved in blood
plasma because the solubility of CO2 is 24 times greater than that
of O2
In short Dalton's law explains how gases move down their pressure gradient
and Henry's law explains how solubility of gas relates to its diffusion.

6. Exchange of gases
Decompression sickness (The Bends):- If diver's ascent is rapid nitrogen comes
out of solution too quickly and forms the bubbles in the tissue.The effect of
decompression sickness typically results from bubbles in nervous tissue.
symptoms include joint pain, dizziness,shortness of breathing and extreme
fatigue.
HYPERBARIC OXYGENATION: Using pressure to cause more O2 to dissolve in
blood is effective in:-
1)- Treating patients infected by anaerobic bacteria (Tetanus)
2)- Used in carbon monoxide poisoning
3)- Gas embolism (gas bubbles in blood stream)

7. External Respiration Internal Respiration
Oxygenated blood
Po2 =100mmHg
PCo2 =40mmHg
Oxygenated blood
Po2 =100mmHg
PCo2 =40mmHg
Deoxygenated blood
Po2 =40mmHg
PCo2=45mmHg
Deoxygenated blood
Po2 =40mmHg
PCo2=45mmHg

8. In a person at rest, tissue cells, on average, need only 25% of the
available O2 in oxygenated blood; despite its name, deoxygenated
blood retains 75% of its O2 content. During exercise, more O2 dif uses
from the blood into metabolically active cells, such as contracting
skeletal muscle fibers. Active cells use more O2 for ATP production,
causing the O2 content of deoxygenated blood to drop below 75%.

9. The rate of pulmonary and systemic gas exchange depends on several factors
1)- Partial pressure difference of gases
2)- Surface area available for gas exchange:The surface area for gaseous
exchange is huge about 70m2
In emphysema surface area is smaller than normal and pulmonary gas
exchange is slowed.
3)-Diffusion distance :- Build up of interstitial fluid between alveoli as occurs in
pulmonary edema slows the rate of gaseous exchange due to increase in
diffusion distance.
4)-Solubility of gases.

10. Transportation of Oxygen and
Carbon dioxide

11. •Oxygen does not dissolve easily in water, so only about 1.5% of
inhaled O2 is dissolved in blood plasma, which is mostly water. About
98.5% of blood O2 is bound to hemoglobin in red blood cells.
•Each 100 mL of oxygenated blood contains the equivalent of 20 mL of
gaseous Oxygen.
.•The heme portion of hemoglobin contains four atoms of iron,
each capable of binding to a molecule of O2
Oxygen and hemoglobin bind to form oxy haemoglobin.
Transportation of Oxygen

12. Transportation of Oxygen
• Oxygen–hemoglobin dissociation
curve showing the
relationship between hemoglobin
saturation and PO2 at normal body
temperature.

13. Other Factors Affecting the Affinity of Hemoglobin
for Oxygen
•1 Acidity:
•Although PO2 is the most important factor that determines the percent O2
saturation of hemoglobin, several other factors influence the tightness or affinity
with which hemoglobin binds O2. In effect these factors shif the entire curve
either to the left (higher affinity) or to the right (lower affinity).
•2 Partial pressure of carbon dioxide.
•3 Temperature.
•4 BPG. A substance found in red blood cells called 2,3-
bisphosphoglycerate (BPG)

14. Other Factors Affecting the Affinity of Hemoglobin
for Oxygen
•1 Acidity:
When pH decreases, the entire oxygen–hemoglobin dissociation curve shif s to the right; at
any given PO2 Hb is less saturated with O2, a change termed the Bohr effect (BOHR). The Bohr
effect works both ways: An increase in H+ in blood causes O2 to unload from hemoglobin, and
the binding of heamoglobin
causes unloading of H+ from hemoglobin.

15. CO2 also can bind to hemoglobin, and the effect is similar to that of H+ (shifting the curve to the
right).
CO2 + H2O H2CO3. H+ + HCO3-
Other Factors Affecting the Affinity of Hemoglobin
for Oxygen
•2 Partial pressure of Co2
The carbonic acid thus formed in red blood cells dissociates into hydrogen ions and bicarbonate
ions. As the H+ concentration increases, pH decreases. Thus, an increased PCO2 produces a more
acidic environment, which helps release O2 from hemoglobin.

16. Other Factors Affecting the Affinity of Hemoglobin
for Oxygen
•3 Temperature:
Within limits, as temperature increases, so does the amount of O2 released from hemoglobin. Heat
is a by-product of the metabolic reactions of all cells, and the heat released by contracting muscle
fibers tends to raise body temperature. Metabolically active cells require more O2 and liberate more
acids and heat.
C6H1206. + 02 CO2 + H2O + ATP + HEAT

17. Other Factors Affecting the Affinity of Hemoglobin
for Oxygen
•4. 2,3 BPG
BPG is formed in red blood cells when they break down glucose to produce ATP in a process called
glycolysis. When BPG combines with hemoglobin by binding to the terminal amino groups of
the two beta globin chains, the hemoglobin binds O2 less tightly at the heme group sites. The
greater the level of BPG, the more O2 unloaded from hemoglobin.

18. Carbon dioxide transport
•1. Dissolved CO2 :
CO2 is transported in blood in three main ways.
The smallest percentage about 7% is dissolved in blood plasma. On reaching the lungs, it
diffuses into alveolar air and is exhaled.
•2. Carbamino haemoglobin:
about 23%, combines with the amino groups of amino acids and proteins in blood to form
carbamino compounds. The main CO2 binding sites are the terminal amino acids in the two
alpha and two beta globin chains. Hemoglobin that has bound CO2 is termed
carbaminohemoglobin (Hb–CO2):
Hb + CO2 Hb–CO2

19. Carbon dioxide transport
•3. Bicarbonate ions:
The greatest percentage of CO2—about 70%—is transported in blood plasma as bicarbonate
ions (HCO3-). As CO2 diffuses into systemic capillaries and enters red blood cells, it reacts with
water in the presence of the enzyme carbonic anhydrase (CA) to form carbonic acid, which
dissociates into H+ and HCO3-.
Thus, as blood picks up CO2, HCO3− accumulates inside RBCs. Some HCO3− moves out into the
blood plasma, down its concentration gradient. In exchange, chloride ions (Cl− ) move from
plasma into the RBCs. This exchange of negative ions, which maintains the electrical balance
between blood plasma and RBC cytosol, is known as the chloride shift.

20. Summary

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