the transport of oxygen in blood
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The transport of oxygen in blood- Haemoglobin
• Hb + 4O2 → Hb(O2)4
• Over 95% of O2 is carried in this way
• Red blood cell (erythrocyte)
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Adaptation of RBC in transport of gases
• Lack a nucleus
• Biconcave disc
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Haemoglobin4 x Haem group + 4 x Polypeptide chain
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The transport of oxygen in blood
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The myogenic control of heartbeat
Bundle of His
Purkinje fibre
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Body tissue身體
肺 Lung
心臟
肺循環pulmonary ci
rculation- to obtain O2 from
the atmosphere
體循環systemic circ
ulation- to release O2 to t
he body tissue
∴ Haemoglobin is exposed to places having different O2 concentration (partial pressure) during the circulation of blood.
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Oxygen dissociation curve
100%
% saturation of haemoglobin
partial pressure of O2 (mmHg)
LungBody tissue
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Significance of the S-shape curve
100%
% saturation of haemoglobin
partial pressure of O2 (mmHg)
Plateau:
► haemoglobin highly saturated with O2 at relatively low O2 partial pressure
► favour the loading of O2 in lung
Steep slope:
► small drop of O2 partial pressure leads to a rapid decrease in % saturation of haemoglobin
► favour the release of O2 in tissue cells
∴ highly effective in the uptake large amount of O2 from environment but release it so easily to the tissue cells !
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Bohr effect – the effect of [CO2] on haemoglobin
100%
% saturation of haemoglobin
partial pressure of O2 (mmHg)
Higher [CO2] e.g. tissue cells
► curve shift to the right
► always at a value of lower % saturation of haemoglobin than the curve at the left
► haemoglobin has a lower affinity to O2
∴ in actively respiring tissue cells, O2 is more easily released by haemoglobin !
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Bohr effect – the effect of [CO2] on haemoglobin
100%
% saturation of haemoglobin
partial pressure of O2 (mmHg)
Lower [CO2] e.g. in lung
► curve shift to the left► haemoglobin has a higher affinity to O2
∴ in well-ventilated alveolus, O2 is more easily taken up by haemoglobin !
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Oxygen dissociation curve of haemoglobin in different animals
% saturation of haemoglobin
partial pressure of O2 (mmHg)
Human
LlamaLugworm
→ Haemoglobin adapted to obtain O2 more easily from the environment !
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Oxygen dissociation curve of haemoglobin in different animals
% saturation of haemoglobin
partial pressure of O2 (mmHg)
Human
→ Haemoglobin adapted to release O2 more easily for active respiring tissues !
Small mammals or birds
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Oxygen dissociation curve: Haemoglobin VS Myoglobin
% saturation of haemoglobin
partial pressure of O2 (mmHg)
Haemoglobin
→ Myoglobin stores O2 in muscles and release it only when the O2 partial pressure is very low.
Myoglobin
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Oxygen dissociation curve:Foetal VS Maternal
% saturation of haemoglobin
partial pressure of O2 (mmHg)
Maternal
→ Foetal haemoglobin has higher affinity to O2 so as obtain O2 from maternal blood in the placenta.
Foetal