Blood , the transport of materials and oxygen dissacociation curves

revision notes on adaptations for tranport part 3 part 1 and 2 are on my resources as transport systems and the heart part 4 transport in plants soon to follow

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Blood and the transport of materials
20. Blood components carry gases haemoglobin carries oxygen as oxyhaemoglobin.
Blood is a tissue made up of 45% cells and 55% fluid
plasma. Plasma is 90% water with food molecules, waste
products, hormones, plasma proteins, mineral ions and
vitamins dissolved in it.
Blood cells:
Erythrocytes or red blood corpuscles
Leucocytes or white blood corpuscles
Red blood cells are filled with the pigment haemoglobin are
biconcave and have no nucleus and this is suited to their
function as oxygen carriage.
The red blood cell just fits the capillaries allowing for
maximum exchange.
White blood cells are either granulocytes which are phagocytic and have granular
cytoplasm and lobed nuclei so they can engulf bacteria or agranulocytes which
produce antibodies and antitoxins have clear cytoplasm and spherical nucleus.
21. The functioning of different types of haemoglobin is demonstrated by plotting oxygen
dissociation curves for normal mammalian haemoglobin compared with foetal haemoglobin.
Each red blood cell contains around 280 million molecules of haemoglobin (4
sub units interlocked)
the partial pressure of oxygen (pO2) is a measure of oxygen concentration
Normal atmospheric pressure = 100Kilopascals
Oxygen partial pressure= 21 kilopascals (oxygen is approximately 21% of the
Most haemoglobin molecules become fully saturated at 8Kpa partial pressure of
oxygen. Oxygen disassociation curve
Red blood cells
pick up oxygen where
the partial pressure is
high (lungs)
disassociates where
there is low pressure
This is illustrated
by the sigmoid shape
of the curve.
pigments have a high
affinity for oxygen at
areas of high
concentration and low
affinity i areas of low partial pressure.

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The amount of oxygen depends on the partial pressure of both oxygen and
carbon dioxide.
When the respiratory pigment is exposed to a gradual increase in oxygen
tension it absorbs oxygen quickly at first but then more slowly giving rise to the
sigmoid shape of the curve.
If the curve is displaced to the right (which it does if CO2 is increased) >>> it less
readily picks up oxygen but will release it more easily.…read more

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Carbon dioxide diffuses into the red blood cell and combines with the water to
form carbonic acid.
Carbonic acid disassociates into H + and HCO3- ions this reaction is catalysed
by carbonic anhydrase,
HCO3 diffuses out of the RBC and combine with Na+ ions found in the blood
plasma to form sodium hydrogen carbonate
H+ ions provide the conditions for the oxyhaemoglobin to disassociate into
oxygen and haemoglobin.…read more

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Capillaries are well adapted to allow the exchange of materials and the cells. In a
closed blood system exchange happens via tissue fluid.
Tissue fluid is formed because of the high hydrostatic pressure of the blood at the
arteriole end of the capillary that pushes fluid out of the blood.
The blood contains plasma proteins giving the blood a relatively high solute potential
(and therefore a low water potential), tending to draw water into the blood.…read more


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