3 Movement of substances across cell membrane
WS 05
Suggested
Answers
Textbook exercise (P. 28 -
32)
M.C.
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1
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2
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3
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4
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5
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6
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7
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8
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C
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B
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C
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D
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A
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B
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B
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A
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(8 marks)
Q. 14 (2 marks)
(a) phospholipids (1) (4)
(b)
ions (1)/ polar or charged
molecules such as glucose, amino acids, proteins water
(c)
acting as ion channels (1)/
trans-membrane carriers/ electron carriers/ enzymes/
receptors/
maintaining structural integrity of membrane
(or state the
function of proteins e.g. for active transport across cell membrane)
(d) antigens (1)/ recognition markers
Q.9 Satisfactory. Some candidates failed to point out
that the glycoprotein on cell membrane serves as a recognition marker.
Q. 18
(a) Cell membrane consists of two
layers of phospholipid (1)
(b) - correct drawing showing integral
proteins and asymmetrical arrangement of peripheral protein (1)
- correct
title (1), e.g. drawing of fluid mosaic
e.g.: phospholipid /
phospholipid bilayer, integral protein, transmemmbrane protein, peripheral
protein, glycoprotein, cholesterol
(c) - some proteins serve as ion
channel / carrier protein for transport of materials across membrane (1)
- Some proteins serve as antigen for cell recognition / receptor site for
receiving chemical messenger (1)
- Fluid nature of the lipid bilayer allows phagocytosis / pinocytosis (1) __(3)_____
7
marks
Q.19
CE-2003-I Q.1(b)
(a) (i) Water potential of RBC is higher than that of surrounding solution……. 1
Water flows out from cells by osmosis……………….…………………. 1
Cells shrink
and become wrinkled …………………………………… 1
(ii) Water potential of some
RBC is higher than that of the surrounding
solution,
but those of others are equal or lower……………………… 1
(b) Wait for a
moment before further observation of the RBC………………… 1
If equilibrium is reached, the ratio of two forms
of RBC should be the same
as
that of previous observation……………………………………………..… 1
(c) Water
potential of RBC is lower than that of surrounding solution………… 1
Water flows into the cells…………………………………………………...... 1
RBC inflate and burst……………………………………………………….. 1
leading to the release of haemoglobin and give
light-red appearance of mixture 1
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(C)
……………………………………………………………………… 1
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Total: 10 + 1
Q.20
(a) (i) When the ratio is 1.0, there is no change in the mass of potato
strips before and after the treatment (1),
indicating that the cells do not have net gain or net loss
of water (1)
by osmosis (1) during the whole process of investigation.
Communication (C) (+1)
(ii) 7%
(1)
(b) The potato strips become faccid (1).
This is because the water potential of
the potato tissues is higher than that of 10% sucrose solution (1),
which leads to net water loss from the
potato tissues (1)
(c) After storage for some time, the water
potential of the potato becomes lower (1).
This may be due to the water loss by evaporation
during the time of storage (1).
(Total: 9 + 1)
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