7 Gas Exchange in Human
2nd Term WS 02
1
(a) Nasal cavity / trachea / bronchi /
bronchioles 1m
(b) The cells need to carry out respiration to
release energy 1m
for the movement of cilia. 1m
(c) Mucus-secreting cells secrete mucus 1m
to trap bacteria. 1m
The cilia beat to sweep mucus
towards the pharynx. The mucus is then swallowed or
coughed up. 1m
2
(a) Refreshing the air in the air sacs
increases the concentration of oxygen in the air sacs.
This helps maintain a higher
oxygen concentration than in the blood. 1m
It also decreases the concentration of carbon
dioxide in the air sacs.
This helps maintain a lower carbon dioxide
concentration than in the blood. 1m
(b) The continuous blood flow in the
capillaries 1m
brings in more carbon dioxide / takes away
more oxygen. 1m
OR
Oxygen combines with haemoglobin 1m
to keep the oxygen concentration
in blood / plasma low. 1m
3
(a) oxyhaemoglobin 1m
(b) lungs 1m
(c) plasma 1m
(d) hydrogencarbonate 1m
(e) water 1m
4
(a) The lungs contain a large number of air
sacs. 1m
(This provides a large surface area
for diffusion of gases.)
(b) The
walls of air sacs are one-cell thick / very thin. 1m
(This reduces the diffusion distance of gases.)
(c) Ventilation brings fresh air to the lungs
to maintain a high oxygen content
in the lungs and to remove carbon
dioxide from the lungs. /
The lungs are richly supplied with
capillary
(which allows oxygenated blood to
be carried away from the air sacs
and deoxygenated blood to be
carried to the air sacs.) 1m
(d) The lungs are deep inside the body. 1m
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