TRANSPORT
OF
RESPIRATORY
GASES
RESPIRATORY GASES; How are they
transported in the blood???
OXYGEN, O2
CARBONDIOXIDE,
CO2
The only way for
Carbondioxide is transported by
Oxygen to be carried
the blood in three ways;
around the body
A)As sodium hydrogencarbonate in
plasma
is by the
HEAMOGLOBIN, in
red blood cells.
B)As carbomino compounds in red
cells
C) In simple solution, dissolved in
the plasma
Transport of O2 by the
Heamoglobin
Inside red blood cells, there are many heamoglobin molecules which are
large globular proteins, each consisting of two alpha subunits and two
beta subunits.
Each subunit has a haem group and a polypeptide globin, This globin
molecule coils around the haem groups which contain iron.
The iron atom can reversibly bond with one molecule of oxygen. Since
it has four subunits, a heamoblobin molecule can combine reversibly with up to
four oxygen molecules forming oxyheamoglobin molecules.
Hb
+
beta1
globin
Red Blood
Cell
alpha1
4O2
HbO8
beta2
Haem
group
alpha2
Transport of O2 by the Heamoglobin
When an heamoglobin molecule is not bonded to oxygen molecule,
deoxyheamoglobin (heamoglobin without O2 molecules) stays in tensed state.
When the first molecule of oxygen combines with a heamoglobin, oxyheamoglobin
shifts to relaxed state in which the shape of heamoglobin changes hence it
becomes easier for other three oxygen molecules to bind to the other haems.
Transport of O2 by the Heamoglobin
 Partial Pressure of Oxygen, pO2
Partial Pressure is the pressure exerted by the one gas in a mixture.
The partial pressure of oxygen (pO2) is a measure of oxygen concentration. The
amount of oxygen that combines depends upon this partial pressure. Heamoglobin
does not necessarily unload all of its oxygen as it passes through the body
tissues.
Heamoglobin requires some conditions in order to load or unload its oxygens.
Conditions for heamoglobin to load
oxygen
Conditions for heamoglobin to
unload oxygen
1
High pO2
Low pO2
2
Low pCO2
High pCO2
3
4
Alkalinity
Inncreased acidity
Lower temperature
Higher temperature
Transport of O2 by the Heamoglobin
Because of the conditions mentioned
before, red blood cells hence
heamoglobins are very efficient in
transporting oxygen from alveoli in
the lungs to the respiring cells in the
tissues.
The tissue fluid surrounds the cells
and supplies them with oxygen. As
the cells respire, they produce
carbondioxide so the tissue fluid
needs to be replaced continually
with the fresh one. In order to
supply cells with oxygen, the red
blood cells move to the lungs where
there is high pO2 and increased
alkalinity. They combine with the
oxygen molecules and move to the
respiring cells where there is high
pCO2 and acidity. As a result, they
give up their oxygens and oxygen
molecules reach respiring cells via
tissue fluid.
Alveoli
Red blood cell
Respiring cells
Tissue fluid
Transport of O2 by theHeamoglobin
The releationship between
the partial pressure of
oxygen and quantity of the
oxygen combined with
haemoglobin is shown by Sshaped DISSOCIATION
CURVES.
Dissociation curve for an adult
Haemoglobin (Hb).
Transport of O2 by theHeamoglobin
As mentioned before, when
heamoglobin combines with first
oxygen molecule, it alters its shape
to anable other molecules to join on
it easily. However as heamoglobin
starts to become fully saturated, it
becomes harder for more oxygen
molecules to join.
◊Steep bits in the middle means that it
is for oxygen molecules to join the
heamoglobin molecules.
◊The shallow parts at each end show
that it is harder now for oxygen
molecules to be loaded.
Transport of Carbondioxide
in the Blood
A)As sodium hydrogencarbonate in plasma
•Carbondioxide, which is produced in respiration, diffuses from body
tissues into the blood where most of it, is taken by the red blood
cells.
•In red blood cells,carbondioxide combines with water to form
carbonic acid, H2CO3. This reaction is catalysed an enyzme called
carbonic anhydrase.
•Then carbonic acid dissociates into hydrogencarbonate and
hydrogen ions.
•Hydrogen ions causes oxyhaemoglobin to dissociate. Therefore
oxygen diffuses into the cells for respiration.
Transport of Carbondioxide in the
Blood
‡ The hydrogen ions combine with haemoglobin and form haemoglobinic acid. This
meas that haemoglobin molecules act as buffers mopping up hydrogen ions and
preventing changes in pH.
ξ Hydrogencarbonate ions are pumped out of the red blood cells and enter the
plasma where they combine with sodium so becoming sodium hydrogencarbonate.
Ξ To make sure that red blood cells remain electrically neutral, chloride ions
move into the red blood cells by a process known as Chloride Shift!
Transport of Carbondioxide in the
Blood
B)As carbomino compounds in red cells
Carbon dioxide also reacts with heamoglobin and other
proteins to form compounds known as CARBOMINO
COPMPOUNDS.
C) In simple solution, dissolved in the plasma
Carbon dioxide is relatively soluble in in the plasma
and a small percentage of it is transported in the form
of a simple solution, dissolved in the plasma.
Ф
BOHR EFFECT Ф
The exact shape of the dissociation curve depends on a number of factors such as
o Partial pressure of carbondioxide (pCO2)
o Temperature
o pH
Because of the Bohr Effect, an increase in partial pessure of carbon dioxide, a
decrease in pH or increased temperature causes hemoglobin to bind to oxygen
with less affinity.
Bohr Effect is very important in respiring tissues since pCO2 increases in tissue
fluid. This causes oxyhaemoglobin to release its oxygens readily causing more
oxygen to be delivered to the tissues needed for respiration.
Ф
BOHR EFFECT Ф
As shown on the dissociation
curve, when carbon dioxide
level increases, the
dissociation curve shifts to
right. This prooves that
more oxygen is released
from the blood.
The lower the saturation of
O2 in the blood, the more O2
will be released.
Different Species Have Different
Dissociation Curves
Hawk; an active animal with a high
Respiratory rate where there is
Plenty of oxygen.
%
saturation
of
haemoglobin
with oxygen
Human
Llama living in Andes; an animal
Living at high attitudes where the
Partial pressure of oxygen is lower
Lugworm, animal living in depleted
Oxygen environment.
Oxygen tension / kPa
Different Species Have Different
Dissociation Curves
%
saturation
of
haemoglobin
with oxygen
Lugworm
Llama
As shown on the dissociation
curve, the chemical composition of
heamoglobin and its oxygen
carrying capacity is different in
different species.
Human
Organisms living in depleted O2
environment have dissociation
Hawk
curves to the left of human ones.
Eg lugworms and Llamas.
Organisms that are active and
have higher partial pressure of
oxygen in their environments have
curves shifting to right of the
human ones. Eg hawks
Oxygen tension / kPa
That means heamoglobins of lugworms
have more affinity for oxygen than
that of the others’.
Ж SUMMARY Ж
≈ Oxygen molecules are transported in the blood by the heamoglobins in the red
blood cells
≈ Carbondioxide molecules are carried by 3 ways; as simple solutions dissolved in
plasma, as carbomino compounds and as sodium hydrogencarbonate
≈ The amount of oxygen that binds to heamoglobin molecules depends on partial
pressure of oxygen. It is a measure of oxygen concentration.
≈ The dissociation curve shows the releationship between the partial pressure of
oxygen and the quantity of oxygen molecules combining with the heamoglobin.
≈ BOHR EFFECT is an effect by which increase in partial pressure of
carbondioxide, decrease in pH and high temperature causes a reduction of the
affinity of heamoglobin for oxygen.
≈ On the dissocaition curves, the curves shifting to left of the others means
increased affinity of oxygen for that heamoglobin.
THE END
Thank You For Listening
Created by Ovgu Ozenli