2016年3月2日 星期三

F4 Biology teaching notes Ch 7: 2nd Term NE 3

A

How is oxygen transported? (Book 1B, p. 7-16)

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
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

n   The oxygen concentration in the air sacs is (6) low / high due to the continuous replacement of air from the external environment.
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) low / high because the body cells in the tissue consume oxygen for respiration.
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.

B

How is carbon dioxide transported? (Book 1B, p. 7-18)

Uptake of carbon dioxide from body tissue
n   The carbon dioxide concentration in the body tissue is (10) low / high because carbon dioxide is continuously produced by body cells through respiration.
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.


Release of carbon dioxide to air sacs
n   The carbon dioxide concentration in the air sacs is (14) low / high because carbon dioxide is continuously removed through exhalation呼氣.
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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