Transcript COSC btec transport of 02 and cO2 Bohr effect missing wrds

Transport of oxygen and
carbon dioxide
Session format
At the end of this lecture the student will be able to:
 understand how O2 and CO2 are transported
around the body.
 describe the structure, function and location of
RBC, haemoglobin and myoglobin.
 describe the oxygen dissociation curve for
haemoglobin.
 understand the Bohr effect.
Recap
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The cardiovascular system is composed of the
heart, blood and
The main job of the cardiovascular system is to
transport respiratory gases (O2 and CO2) around
the body.
This is in the form of oxygenated and
deoxygenated blood.
Q: Which blood has the highest concentration of
CO2; oxygenated or deoxygenated blood?
Recap
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During exercise the demand for oxygen
Especially at the
This is because O2 is required for the production
of
(Energy).
The energy is used for muscular contraction and
hence movement of the body.
During exercise the cardiac output is increased by
increasing
Recap
Remember that:
 Heart rate is the amount of heart beats per
minute.
 Stroke volume is the amount of blood ejected
from the heart with each beat.
 Cardiac output is the total amount of blood
pumped out of the heart in one minute.
 Cardiac output =
Recap
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Sympathetic activity =
Parasympathetic activity =
Increase in heart rate is due to an increase in
sympathetic activity.
Accompanied by a decrease in parasympathetic
activity.
Hormonal control by adrenaline and
Recap
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Blood is shunted away from certain organs during
exercise and redirected to the working muscles.
“Supply and Demand”
This is achieved through vasoconstriction and
vasodilation of the
Q: Will the blood vessels supplying the working
muscles vasodilate or vasoconstrict during
exercise?
Transport of O2
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Oxygen picked up by the blood at the lungs (
) must be transported to the tissues.
Oxygen is transported in the blood in two forms:
– physically dissolved in the blood (
– bound to haemoglobin (
)
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)
Very little O2 is dissolved in the plasma of the
blood as it poorly soluble.
Due to the small amount of O2 dissolved in the
blood there must be an additional mechanism of
transporting oxygen from the lungs to the tissues.
Transport of O2
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This mechanism is
(Hb)
Haemoglobin - iron bearing protein molecule
contained within red blood cells (RBC).
280 million haemoglobin molecules crowded into
each RBC.
Men have
more haemoglobin than women.
Due to male testosterone increasing RBC
production.
Haemoglobin has the ability to form a reversible
combination with oxygen.
Q: What does reversible mean?
Transport of O2
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When not combined to O2, haemoglobin is
referred to as reduced haemoglobin.
When combined with O2, it is called
Hb +
Haemoglobin
O2
Oxygen
HbO2
Oxyhaemoglobin
Transport of O2
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The haemoglobin molecule has four atoms of iron.
Each of the four iron atoms has the ability to
combine with
.
Each Hb molecule can carry up to 4 molecules of
O2.
Hb is considered to be fully saturated when all
iron atoms combine with a molecule of O2.
Transport of O2
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The percent haemoglobin saturation (%Hb) is a
measure of the extent to which Hb in the blood is
combined with O2.
Can vary from 0 to 100%
100% = all of the haemoglobin molecules within
the blood are fully saturated with O2.
Healthy individuals =
Hb
Influenced by PO2 of the blood.
PO2 = partial pressure of Oxygen. Caused by
movement of dissolved oxygen in the blood.
Transport of O2
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Gases (O2 and CO2) move down partial pressure
gradients.
PO2 is high at the
(pulmonary capillaries).
PO2 is low at the
(systemic capillaries).
When PO2 is high oxygen combines readily with
haemoglobin, until the haemoglobin becomes
saturated. Called oxygenation
When the PO2 is low haemoglobin releases O2 to
the tissues. Called deoxygenation
Transport of O2
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Because of the difference in PO2 at the lungs and
the tissues, Hb automatically loads up on oxygen
at the lungs (oxygenation) and unloads it at the
tissues (deoxygenation).
The relationship between PO2 and % haemoglobin
saturation is known as the:
Oxygen -Haemoglobin Dissociation Curve
S - shaped curve (see graph)
Oxygen - Haemoglobin Dissociation Curve
100
80
% sat
of Hb
60
40
20
0
0
20
40
60
PO2
80
100
Transport of O2
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Note: from the Oxygen haemoglobin dissociation
curve that the % saturation of haemoglobin is
higher at the lungs and lower at the tissues.
Oxygen is attaching to haemoglobin at the lungs
Oxygen is unloading
The Bohr effect
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Oxygen - haemoglobin curve shown previously is
at normal conditions (pH 7.4, tissue Temp of
37oC).
Any increase in acidity, temperature or
concentration of carbon dioxide causes the
dissociation curve to shift downwards and to the
right.
In other words the haemoglobin releases oxygen
more readily.
Known as the
The Bohr Effect
100
80
% sat
of Hb
rightward shift due to increased
carbon dioxide, acidity and temp.
60
40
20
CO2, acidity, Temp
0
0
20
40
60
PO2
80
100
Carbon Monoxide
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Carbon Monoxide (CO) is a poisonous gas.
Found in such things as motor car fumes.
Carbon Monoxide and Oxygen compete for the
same binding sites on Haemoglobin.
CO is
times more likely to attach to
haemoglobin than O2.
Therefore if CO is present
oxygen is
transported in the blood.
Death can occur due to oxygen starvation of the
tissues.
Myoglobin
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Myoglobin is an iron containing protein.
Found in skeletal and
muscle
It’s function is as a storage site for
.
Similar to haemoglobin - combines reversibly with
oxygen.
Each myoglobin molecule contains 1 iron atom, in
contrast to haemoglobin which contains 4 atoms.
High concentration of myoglobin in slow twitch
muscle fibres (generate ATP aerobically).
Myoglobin
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Facilitates (helps) the transfer of oxygen to the
tissues.
Especially during beginning of exercise and during
During rest and moderate levels of exercise the
myoglobin stays attached to the oxygen.
Unlike haemoglobin, myoglobin is not affected by
acidity, carbon dioxide and temperature.
Therefore does not display the
Transport of Carbon dioxide (CO2)
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Remember - gases flow
a pressure
gradient.
When blood flows through the tissue capillaries
CO2 diffuses down its pressure gradient from the
tissue cells into the blood.
The blood then becomes
.
CO2 is produced as a by product of metabolism
(energy production).
Transport of Carbon dioxide (CO2)
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CO2 is transported in the blood in three ways:
– physically dissolved (10%)
– bound to haemoglobin (30%)
– as bicarbonate (
)
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When CO2 combines with haemoglobin the
product is known as carbomino-haemoglobin
(HbCO2).
The unloading of O2 at the tissues facilitates the
picking up of CO2 by Haemoglobin.
Transport of Carbon dioxide (CO2)
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By far the most important means of transporting
CO2 from the tissues to the lungs is as a
bicarbonate (HCO3-).
60% of the CO2 is converted to a bicarbonate.
The chemical reaction takes place in the
It is essential both at rest and during exercise
that O2 and CO2 are transported around the body.
This is achieved through various mechanisms
within the blood.