Cell Membranes and Transport
May/June
5
(b) Name two assimilates that move from the palisade mesophyll cells to the vascular
tissue to be exported from the leaf.
For
Examiner’s
Use
1 .......................................................................................................................................
2 .................................................................................................................................. [2]
(c) Explain, using the term water potential, how water moves from the vascular tissue to
the atmosphere.
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[Total: 12]
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9700/02/M/J/05
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Cell Membranes and Transport
May/June
For
Examiner’s
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12
6
Fig. 6.1 shows a diagram of a plasma (cell surface) membrane.
K
L
M
N
Fig. 6.1
(a) Indicate, by putting a circle,
membrane shown in Fig. 6.1.
0.7 nm
7.0 nm
70 nm
, around one of the following, the width of the
7 × 10–5 m
700 µm
7.0 µm
[1]
(b) Outline the functions of the following components of the plasma membrane.
K ......................................................................................................................................
..........................................................................................................................................
L ......................................................................................................................................
..........................................................................................................................................
M ......................................................................................................................................
..........................................................................................................................................
N ......................................................................................................................................
......................................................................................................................................[4]
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May/June
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(c) Some substances may cross plasma membranes by simple diffusion. Glucose, however,
does not.
For
Examiner’s
Use
Explain why glucose cannot pass across membranes by simple diffusion.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
......................................................................................................................................[2]
(d) In an investigation, animal cells were exposed to different concentrations of glucose. The
rate of uptake of glucose into the cells across the plasma membrane was determined
for each concentration. Fig. 6.2 shows the results.
rate of uptake
of glucose by
cells / arbitrary
units
22
20
18
16
14
12
10
8
6
4
2
0
0
5
10
15
20
25
30
35
40
concentration of glucose / arbitrary units
Fig. 6.2
Using the information in Fig. 6.2, explain how the results of the investigation support the
idea that glucose enters cells by facilitated diffusion.
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......................................................................................................................................[2]
QUESTION 6 CONTINUES ON PAGE 14
© UCLES 2007
9700/02/M/J/07
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Cell Membranes and Transport
May/June
For
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Use
14
(e) State how active transport differs from facilitated diffusion.
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..........................................................................................................................................
......................................................................................................................................[1]
[Total: 10]
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May/June
12
5
Fig. 5.1 shows part of a transverse section of a leaf.
For
Examiner’s
Use
Q
R
Fig. 5.1
(a) Explain, in terms of water potential, how water moves from Q to R.
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9700/02/M/J/09
Cell Membranes and Transport
May/June
11
5
(a) Fig. 5.1 represents a molecule of a triglyceride.
For
Examiner’s
Use
Name the components A and C and name the bond B.
Write your answers on the dotted lines provided in Fig. 5.1.
A .........................................................
B .........................................................
C .........................................................
Fig. 5.1
[3]
(b) A phospholipid is sometimes described as a modified triglyceride.
(i)
State how the structure of a phospholipid differs from a triglyceride.
..................................................................................................................................
..................................................................................................................................
.............................................................................................................................. [2]
(ii)
Explain how a phospholipid is suited to its role in cell membranes.
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.............................................................................................................................. [3]
© UCLES 2011
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Cell Membranes and Transport
May/June
4
2
Fig. 2.1 shows a drawing made from an electron micrograph of two adjacent cells in a leaf.
A
B
C
D
E
F
G
vacuole
Fig. 2.1
(a) Structures A and B are both visible using the light microscope, but the internal detail of
these organelles shown in Fig. 2.1 is only visible using the electron microscope.
Explain why the internal details of structures A and B are only visible when using the
electron microscope and not when using the light microscope.
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Examiner’s
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Cell Membranes and Transport
May/June
5
(b) Name in full the structures labelled C, D and E.
C .......................................................................................................................................
For
Examiner’s
Use
D .......................................................................................................................................
E ................................................................................................................................. [3]
(c) State one role of vacuoles in plant cells.
..................................................................................................................................... [1]
(d) Structures F and G have very different permeability properties.
Explain how the composition of structures F and G determines the permeability
properties of these structures.
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(e) Fig. 2.1 shows two plasmodesmata connecting the adjacent cells.
Describe the roles of plasmodesmata in transport in plants.
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[Total: 14]
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Cell Membranes and Transport
May/June
2
1
One role of the cell surface membrane is to control the entry and exit of substances.
(a) Complete Table 1.1 to show the transport mechanisms across cell surface membranes
and examples of materials transported.
Table 1.1
transport mechanism across cell
surface membrane
active transport
example of material transported across
membrane
sodium ions
oxygen molecules
bacteria
exocytosis
mucin (for mucus)
facilitated diffusion
osmosis
[2]
© UCLES 2012
9700/22/M/J/12
For
Examiner’s
Use
Cell Membranes and Transport
May/June
3
(b) Each transport mechanism across cell surface membranes has a characteristic set of
features.
For
Examiner’s
Use
In each of the boxes below, state one example of a transport mechanism that matches
the pathway shown.
passive
yes
active
specific transport
protein involved
passive
no
active
[4]
[Total: 6]
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May/June
10
5
Fig. 5.1 shows a section of a cell surface membrane.
For
Examiner’s
Use
P
Q
W
R
Fig. 5.1
(a) State the functions of structures P, Q and R.
P ......................................................................................................................................
..........................................................................................................................................
Q ......................................................................................................................................
..........................................................................................................................................
R ......................................................................................................................................
..................................................................................................................................... [3]
(b) Circle the width of the membrane shown as W in Fig. 5.1.
17.0 μm
1.7 μm
0.7 μm
70.0 nm
17.0 nm
7.0 nm
0.7 nm
[1]
(c) Membranes, such as the cell surface membrane, are described as having a fluid mosaic
structure.
Explain what is meant by the term fluid mosaic.
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..........................................................................................................................................
..................................................................................................................................... [2]
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Cell Membranes and Transport
May/June
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(d) Aquaporins are membrane channel proteins in plant and animal cells. They permit the
movement of water across membranes. Explain why they are necessary.
For
Examiner’s
Use
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[Total: 9]
6
(a) Explain how uncontrolled cell division can result in cancer.
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(b) Describe the experimental evidence that shows that smoking causes lung cancer.
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..................................................................................................................................... [3]
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Cell Membranes and Transport
May/June
10
In some organisms, trehalose is used as an energy store and gives protection against
the harmful effects of very low temperatures. Trehalose is sometimes referred to as a
cryoprotectant, allowing organisms to survive in freezing conditions.
Freezing temperatures can damage the cell surface membrane and membranes within the
cell.
(c) Explain the importance of the cell surface membrane to cells.
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..........................................................................................................................................
..................................................................................................................................... [3]
(d) Freezing temperatures can also completely stop enzyme activity by causing the
molecules to undergo ‘cold denaturation’. Enzyme activity is not recovered when
temperatures are increased to a normal working temperature range.
(i)
Explain the mode of action of enzymes.
..................................................................................................................................
..................................................................................................................................
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............................................................................................................................. [3]
(ii)
Suggest how the molecular structure of the enzyme changes during ‘cold
denaturation’.
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..................................................................................................................................
............................................................................................................................. [2]
© UCLES 2013
9700/22/M/J/13
For
Examiner’s
Use
Cell Membranes and Transport
May/June
3
(c) The membrane surrounding the vacuole, called the tonoplast, has a fluid mosaic
structure.
For
Examiner’s
Use
Describe the structure of this membrane.
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..................................................................................................................................... [4]
(d) Palisade mesophyll cells have very large vacuoles.
Explain how water moves from the xylem in the leaf into these vacuoles.
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..........................................................................................................................................
..........................................................................................................................................
..........................................................................................................................................
..................................................................................................................................... [3]
[Total: 12]
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