hour 1-gaseous exchange
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7.1 Gaseous exchange and
control in mammals
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Describe the basic structure of
haemoglobin and its characteristics as
respiratory pigments. Explain the transport of carbon dioxide
by haemoglobin.
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Consist of four
polypeptide subunits;
two chain
two chain
held together by
hydrogen bond
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Structure of haemoglobin
Each peptide contains
a haem group, bind
with oxygen
Therefore, one
hemoglobin (Hb)
molecule binds
up to fouroxygen molecules
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Combines reversely with O2 to formoxyhaemoglobin in areas of high O2
concentration region
- releases O2in areas of low O2
concentration region
Hb + 4O2 Hb(O2)4
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1
dissolved in
blood plasma
2
as Carbamino-
Haemoglobin
3
as
bicarbonate
ions (HCO3-)
CO2 transportation in blood
CO2
is transported between respiring tissues and
the lungs in 3 different ways:
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Air inAir inLungLung
TissueTissueFluidFluid
RBCRBC
Plasma inPlasma inCapillaryCapillary
1.1. COCO22 diffusesdiffuses
through tissuethrough tissuecapillary wallcapillary wall
DissolvesDissolves
in plasmain plasma,,
AsAsHCOHCO
33-,-,
Bound toBound tohemoglobin.hemoglobin.
2.2. COCO22is carriedis carriedto the lungsto the lungs
3.3. COCO22diffusesdiffuses
through lungthrough lungca illary wallcapillary wall
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Only about 7% of the CO2 released by respiring cells
is transported/dissolved in blood plasma
In plasma,CO2
slowly combine with water to form
carbonic acid
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About 23% CO2
binds to amino
ends of the hemoglobin
polypeptide chain to form
carbaminohemoglobin
the amount of CO2 that is able
to combine with Hb depends onthe amount of O2 already being
carried by the Hb
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3. As
bicarbonate ion (HCO3
-)
About 70% is transported in the blood in the form
of bicarbonate ions (HCO3
-)
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3. As
bicarbonate ion (HCO3
-)
CO2
diffuses passively into
bloodstream and passes into the
erythrocytes.
- combines with water to form
carbonic acid H2CO
3(catalysed by
carbonic anhydrase)- then dissociates into H+ and
HCO3
-
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Accumulation of H+ will
lower the pH of its surrounding
H+
tend to displace O2 fromhaemoglobin and make less
affinity of haemoglobin for
oxygen
this is called the Bohr effect
3. As
bicarbonate ion (HCO3
-)
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Hb accepts H+ fromcarbonic acid forming
haemoglobinic acid (HHb)
Hb acts as a buffermolecule (to minimize
the change in blood pH)
3. As
bicarbonate ion (HCO3
-)
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this enables large
quantities of carbonic acidto be carried to the lungs
without any major
alteration in blood pH
3. As
bicarbonate ion (HCO3
-)
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most of bicarbonate ions
diffuse out into the plasma,
where it is carried in the
bloodstream to the lungschloride ions (Cl-) in the
plasma diffuse into
erythrocytes to replace
bicarbonate ions
3. As
bicarbonate ion (HCO3
-)
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This is to balance the
loss of bicarbonate ion,
and to maintain the
electrical balance betweenblood plasma and
erythrocyte
this is called chlorideshift
3. As
bicarbonate ion (HCO3-)
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1
dissolved in
blood plasma
2
as Carbamino-
Haemoglobin
3
as
bicarbonate
ions (HCO3-)
CO2 transportation in blood
CO2 is transported between respiring tissues and
the lungs in 3 different ways:
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17.1 Gaseous exchange and control in mammals
c) describe the oxygen dissociation curve of
haemoglobin
d) compare oxygen dissociation curve of
haemoglobin and myoglobin
c) explain Bohr effect due to partial pressure
of carbon dioxide