A
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How is oxygen
transported? (Book 1B, p. 7-16)
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Ø Oxygen is mainly
transported by (1) red blood cells in the blood.
Ø Adaptive features
of red blood cells for carrying oxygen:
Feature
|
Adaptation
|
(2)
Biconcave
disc
shape (雙凹圓盤狀)
|
n Provides
a large (3) surface area to volume ratio for the
diffusion of oxygen
n Provides
a short distance for oxygen to
reach and leave the haemoglobin in the red blood cells rapidly
|
No (4) nucleus when mature
|
n
Provides more room for holding haemoglobin
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Fully packed with
(5) haemoglobin (血紅蛋白)
|
n Allows the red blood cells to carry a large amount
of oxygen
Fig
5: Structure of red blood cell & haemoglobin
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n The oxygen
concentration in the air sacs is
(6)
n Oxygen in the air sacs diffuses into red blood cells.
n Oxygen combines with haemoglobin to form (7) oxyhaemoglobin
(氧合血紅蛋白), which gives the blood a bright red colour.
Haemoglobin (purplish red)
+ oxygen → oxyhaemoglobin (bright red)
n The
red blood cells containing oxyhaemoglobin are then carried to the body
tissue.
|
n
The oxygen concentration in the body tissue is (8)
n
Oxyhaemoglobin in the red blood cells breaks down into haemoglobin and
oxygen.
oxyhaemoglobin → haemoglobin + oxygen
n The
oxygen diffuses into the body cells and the blood becomes (9) purplish red.
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B
|
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How is carbon dioxide
transported? (Book 1B, p. 7-18)
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Uptake of carbon
dioxide from body tissue
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n
The carbon
dioxide concentration in the body tissue is (10)
n
Most carbon dioxide diffuses into red blood cells and reacts with (11) water to form
(12) hydrogencarbonate
ions (碳酸氫鹽離子).
n The hydrogencarbonate ions diffuse out of the red
blood cells and are carried by the
(13) plasma to the air sacs.
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Release of carbon
dioxide to air sacs
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n
The carbon
dioxide concentration in the air sacs is (14) low /
n Hydrogencarbonate
ions in the plasma enter the red blood cells and break down into carbon dioxide and water.
n
The carbon dioxide diffuses into the plasma and then into the air
sacs, and is finally exhaled
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