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
9.
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.