TRANSPORT OF CO2 AND O2

1. TRANSPORT
OF
GASES
BY:
Mrs.Keerthi Samuel,
Asst.Professor,
Vijay Marie CON

3. OXYGEN TRANSPORT
• Oxygen does not dissolve in the water easily.
• At least 1.5% of inhaled oxygen is dissolved in blood
plasma which is mostly water.
• About 98% of blood oxygen is bound to hemoglobin in
RBC’s.
• Each 100ml of oxygenated blood contains equivalent
of 20 ml of gaseous oxygen.

4. OXYGEN TRANSPORT
 Heme portion of the Hb contains 4 atoms of iron each capable of
binding to a molecule of O2.
 Oxygen and hemoglobin bind to form OXYHEMOGLOBIN.
 The 98.5% of oxygen that is bound to Hb is trapped inside
RBC’s.
 So only dissolved oxygen (1.5%) can diffuse out of tissue
capillaries into the tissue cells.

5. RELATION BETWEEN Hb AND PARTIAL PRESSURE
 The most important factor that determines how much
oxygen binds to Hb in Po2.
 Higher the Po2 more oxygen combines with Hb.
 When the Hb is completely converted into Oxyhemoglobin-
FULLY SATURATED
 When there is a mixture of Hemoglobin and oxyhemoglobin
– PARTIALLY SATURATED.
 EX: if Hb molecule has bound to 2 molecules of oxygen the we
call the Hb is 50 % saturated.

6. OXYGEN-HEMOGLOBIN DISSOCIATION CURVE
 It gives us the relation between the percentage of saturation of Hb
and Partial pressure of oxygen.
 When Po2 is high , the Hb binds with large amounts of oxygen and
is almost 100% saturated.
 When Po2 is less or, Hb is only partially saturated.
 Oxygen will bind to Hb, until all the available molecules are
saturated.
 When the P02 is between 60-100mmHg, Hb is more saturated with
oxygen.

7. OTHER FACTORS
PH (or) ACIDITY
• As acidity increases the affinity of Hb for o2
decreases and o2 readily dissociates from Hb.
• In other words increase in acidity enhances
unloading of o2 from hemoglobin.
• When the PH decreases the Hb is less saturated
with o2 a phenomenon called ‘THE BOHR EFFECT’
• As increase in H+ in blood causes oxygen to unload
from the Hb and the bnding of O2 to Hb ceases.
TEMPERATURE
• As the temperature increases- the amount of co2
released from Hb increases.
• Heat is a byproduct of all metabolic reactions of
cells and the heat released by contracting
muscle fibers liberates more acid and heat.
• Acid and heat in turn promotes release of oxygen
from Hb.
• Fever produces same effects but in hypothermia
more oxygen remains bound to Hb.

8. PARTIAL PRESSURE OF CO2
• CO2 binds to hemoglobin .
• As the pco2 rises ,Hb releases co2 more readily.
• As co2 enters the blood , much of t is temporarily
converted into carbonic acid , a reaction catalyzed by an
enzyme in RBC’s called carbonic anhydrase.
• The carbonic acid again dissociates into H+ ions which
decreases the PH and Hco3 ions.
• Thus the increased Pco2 produces more acidic
environment which helps release O2 from Hb.
OTHER FACTORS

10. CARBONDIOXIDE TRANSPORT
• Under normal conditions, each 100ml of
deoxygenated blood contains the equivalent of
53ml of gaseous CO2 which is transported in
three main ways:
• DISSOLVED CO2
• CARBAMINO COMPOUNDS’
• BICARBONATE IONS

11. 1.DISSOLVED CO2
• The smaller percentage that is about 7% is dissolved
in plasma.
• Upon reaching the lungs, it diffuses into alveolar air
and is exhaled.

12. 2.CARBAMINO COMPOUNDS
• 23% of Co2 combines with amino groups of amino
acids and proteins in the blood to form carbamino
compounds.
• Hb that has bound to Co2 turns into
Carbaminohemoglobin

13. 3.BICARBONATE IONS
• The greatest percentage of Co2 about 70% is
transported in blood plasma as bicarbonate ions.
• As co2 diffuses into systemic capillaries and enters
RBCs , it reacts with water in the presence of carbonic
anhydrase which dissociates into H+ and Hco3-.
• Thus blood picks up Co2 and Hco3- accumulates in
the RBCs.

14. 3.BICARBONATE IONS
• Some Hco3- moves out into plasma down its concentration
gradient .
• In exchange chloride moves from plasma to RBCs
• This exchange of negative ions is called CHLORIDE SHIFT.
• This maintains electrical balance between blood plasma and
RBCs
• The lower the amount of Oxyhemoglobin the higher is the
oxygen carrying capacity of blood .this relation is called
HALDANE EFFECT.