Transport of Oxygen and Carbon Dioxide.ppt

transport of gases

1. RESPIRATION
PRASETYASTUTI
BIOCHEMISTRY DEPARTMENT
FACULTY OF MEDICINE UGM

2. •RESPIRATION
: The interchange of O
2 & CO
2 between the
body and its environment
Processes :
1. Pulmonary ventilation
2.The difusion O
2 & CO
2 between the
alveoli and the blood
3.The transport of O
2
& CO
2
to and from
the cells of the organism via the blood
4.The regulation of ventilation

3. External Respiration/pulmonary gas exchange
: the diffusion of O2 from air in the alveoli of the
lungs to the blood in pulmonary capillaries and
diffusion of CO2 from the blood in pulmonary
capillaries to the air in the alveoli of the lungs
Internal Respiration/ systemic gas exchange
: The exchange of O2 and CO2 between systemic
capillaries and tissue cells

4. The pressure of a specific gas in a mixture is
called its partial pressure (P
x
)
The total pressure of the mixture :
by adding all the partial pressures
Atmospheric pressure (760 mmHg)
P
N2
+ P
O2
+ P
H2O
+ P
CO2
+ P
other gases

5. •The partial pressure determine the movement
of O2 and CO2 between :
•- the atmospheric and lungs
- the lungs and blood
- the blood and body cells.
Each gas diffuses across a permeable membrane
from the area where its partial pressure is
greater to the area where its partial pressure
is less.
The greater the difference in partial pressure,
the faster the rate of diffusion

6. •Atmospheric air contains
•Nitrogen : 78.62%
•Oxygen : 20.84%
•Carbon dioxide : 0.04%
•Water : 0.5%
•At 37
o
C, the water vapor pressure is 47
mmHg -
•The sum of the partial pressures of the other
components of air must contribute
•760 – 47 = 713 mmHg

7. Much more CO2 is dissolved in blood
plasma because the solubility of CO2 is
24 times greater than that of O2
N2 , has no known effect on bodily
functions --
At sea level pressure very little it
dissolves in blood plasma because its
solubility is very low

8. Solubility coefficients gases in water at 37
o
C
and 1 atm of pressure
•Oxygen 0.024
•Carbon dioxide 0.57
•Carbon monoxide 0.018
•Nitrogen 0.012
•Helium 0.008

9. The rate of diffusion process be influenced by
- the difference between the partial pressure
of the gas above the liquid and its tension
within it
- the cross-sectional area of the gas-liquid
interphase
- the distance the molecules
- the solubility of the gas in the liquid
- velocity/kinetic movement of the molecules

10. The rate of pulmonary and systemic gas
exchange depends on :
1. Partial pressure difference of the gases
2. Surface area available for gas exchange
3. Diffusion distance
4. Molecular weight and
5. solubility of gases

PD X A X S
DR α -------------------
D √MW

11. Transport of Oxygen and Carbon
Dioxide

12. Oxygen Transport
•O
2 is transported by the blood either,
– Combined with haemoglobin (Hb) in the red blood
cells (>98%) or,
–Dissolved in the blood plasma (<2%).

13. Oxygen Transport
•The resting body requires 250ml of O2/
minute.
•We have four to six billion haemoglobin
containing red blood cells.
•The haemoglobin allows nearly 70 times more O
2

than dissolved in plasma.

14. Haemoglobin
Haemoglobin molecules can
transport up to four O2’s
When 4 O2’s are bound to
haemoglobin, it is 100% saturated,
with fewer O2’s it is partially
saturated.
Oxygen binding occurs in
response to the high PO2 in the
lungs
Co-operative binding:
haemoglobin’s affinity for
O2 increases as its
saturation increases.

15. Haemoglobin Saturation
•Haemoglobin saturation is the amount of
oxygen bound by each molecule of
haemoglobin
•Each molecule of haemoglobin can carry four
molecules of O2.
•When oxygen binds to haemoglobin, it forms
OXYHAEMOGLOBIN;
•Haemoglobin that is not bound to oxygen is
referred to as DEOXYHAEMOGLOBIN.

16. Haemoglobin Saturation
•The binding of O
2
to haemoglobin depends on
the PO
2
in the blood and the bonding
strength, or affinity, between haemoglobin
and oxygen.
•The graph on the following page shows an
oxygen dissociation curve, which reveals the
amount of haemoglobin saturation at
different PO
2
values.

17. The Oxygen Dissociation Curve
•Reveals the amount of
haemoglobin saturation
at different PO
2 values.

18. The Oxygen Disassociation Curve
Haemoglobin saturation is
determined by the partial
pressure of oxygen. When these
values are graphed they produce
the Oxygen Disassociation Curve
In the lungs the partial
pressure is approximately
100mm Hg at this Partial
Pressure haemoglobin has
a high affinity to 02 and is
98% saturated.
In the tissues of other
organs a typical PO2 is 40
mmHg here haemoglobin
has a lower affinity for O2
and releases some but not
all of its O2 to the tissues.
When haemoglobin leaves
the tissues it is still 75%
saturated.

19. Haemoglobin Saturation at High Values

Lungs at sea level:
PO2 of 100mmHg
haemoglobin is 98%
SATURATED
Lungs at high
elevations: PO2
of 80mmHg,
haemoglobin 95
% saturated
Even though PO2
differs by 20 mmHg
there is almost no
difference in
haemoglobin
saturation.
When the PO2 in the
lungs declines below
typical sea level values,
haemoglobin still has a
high affinity for O2 and
remains almost fully
saturated.

20. Haemoglobin Saturation at Low Values

21. Factors Altering Haemoglobin
Saturation

22. Factors Altering Haemoglobin
Saturation (Exercise)

23. Factors Affecting Haemoglobin
Saturation
•Blood acidity…
•Blood temperature…
•Carbon Dioxide concentration

24. Factors affecting Disassociation
BLOOD TEMPERATURE
•increased blood temperature
•reduces haemoglobin affinity for O
2
•hence more O
2 is delivered to warmed-
up tissue
Respiratory Response to Exercise
BLOOD Ph
•lowering of blood pH (making blood
more acidic)
•caused by presence of H
+
ions from
lactic acid or carbonic acid
•reduces affinity of Hb for O
2
•and more O
2
is delivered to acidic sites
which are working harder
CARBON DIOXIDE CONCENTRATION
•the higher CO
2
concentration in tissue
•the less the affinity of Hb for O
2
•so the harder the tissue is working, the
more O
2
is released

25. Key Point
•Increased temperature and hydrogen ion
(H
+
) (pH) concentration in exercising
muscle affect the oxygen dissociation
curve, allowing more oxygen to be
uploaded to supply the active muscles.

26. Carbon Dioxide Transport
•Carbon dioxide also relies on the blood fro
transportation. Once carbon dioxide is
released from the cells, it is carried in the
blood primarily in three ways…
•Dissolved in plasma,
•As bicarbonate ions resulting from the
dissociation of carbonic acid,
•Bound to haemoglobin.

27. Dissolved Carbon Dioxide
•Part of the carbon dioxide released from the
tissues is dissolved in plasma. But only a small
amount, typically just 7 – 10%, is transported
this way.
•This dissolved carbon dioxide comes out of
solution where the PCO
2
is low, such as in the
lungs.
•There it diffuses out of the capillaries into the
alveoli to be exhaled.

28. In Review
1)Oxygen is transported in the blood primarily
bound to haemoglobin though a small amount
is dissolved in blood plasma.
2)Haemoglobin oxygen saturation decreases.
1)When PO2 decreases.
2)When pH decreases.
3)When temperature increases.

29. In Review
Each of these conditions can reflect increased
local oxygen demand. They increase oxygen
uploading in the needy area.
3) Haemoglobin is usually about 98% saturated
with oxygen. This reflects a much higher
oxygen content than our body requires, so the
blood’s oxygen-carrying capacity seldom limits
performance.

30. In Review
4) Carbon dioxide is transported in the blood
primarily as bicarbonate ion. This
prevents the formation of carbonic acid,
which can cause H+ to accumulate,
decreasing the pH. Smaller amounts of
carbon dioxide are carried either
dissolved in the plasma or bound to
haemoglobin