8 Transport in humans I
2nd Term WS 05
1
(a) P: blood platelet 1m
It is involved in blood clotting. 1m
Q: red blood cell 1m
It contains haemoglobin to carry oxygen. 1m
R: white blood cell 1m
It protects our body against diseases. 1m
(b) Plasma 1m
(c) Red
blood cells 1m
2
(a) X: phagocyte 1m
Y: red blood cell 1m
Z: lymphocyte 1m
(b) Cell Y has a biconcave disc
shape. 1m
There is less cytoplasm at the centre and
thus fewer haemoglobin molecules. 1m
(c) Its biconcave disc shape
increases the surface area to volume ratio. 1m
This allows oxygen to diffuse in and out of the cells
more efficiently.
/ This provides a short distance for oxygen
to reach and leave the haemoglobin in the cell rapidly. 1m
OR
It has no nucleus when mature. 1m
This provides more room for holding
haemoglobin.
/ It is fully packed with haemoglobin which is an excellent oxygen
carrier. 1m
(d)
|
X
|
Z
|
Shape of the
nucleus
|
Lobed
|
Round
|
Role in body
defence
|
It engulfs
germs by phagocytosis.
|
It produces
antibodies to kill germs.
|
1m x 4
3
(a) (i) Vein 1m
(ii) Artery 1m
(b) The blood pressure in Y is higher than that
in X. 1m
The blood pressure in Y is high due to the pumping action of the heart.
1m
The blood pressure in X is low as the blood has overcome great
resistance
of the blood vessel walls after travelling for a long distance. 1m
(c) X has a larger lumen 1m
to reduce the resistance to blood flow. 1m
Y has a thicker wall, 1m
which allows it to withstand
high blood pressure. 1m
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