Download public exam_movement of substances across cell membrane

ECF Saint Too Canaan College
Biology public exam exercise
Movement of substances across cell membrane
Name: ___________________
Class: ______ (
)
Date: _____________________
CE 2000_I_Q.3(c)
1. To study the effect of sucrose solution on plant cells, a student used the lower epidermis of a
Rhoeo discolor leaf, the cells of which contain a red pigment. He mounted a piece of the lower
epidermis in a sucrose solution. He then observed the epidermis under the microscope immediately
and after 10 minutes.
The photomicrographs below show the conditions of the same epidermal cells under the low power
of the microscope :
(a)
Describe and explain the change in the appearance of cell A 10 minutes after mounting.
(4 marks)
(b)
Suggest a reason why cell B did not show the same change as cell A.
(1 mark)
(c)
The student wanted to examine cell A under the high power of the microscope.
(i)
State one action that he might need to take before turning to the high power objective.
(1 mark)
(ii)
State two actions that he might need to take after turning to the high power objective.
(2 marks)
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CE 2003_I_Q.1(b)
2. A student carried out a study on the effect of two different sodium chloride solutions on red blood
cells. He added a drop of citrated mammalian blood to 2 cm3 of each solution in separate test
tubes, A and B. After five minutes, the mixtures in both tubes appeared light red in colour. He
then examined a drop of each mixture under the microscope. After repeated examinations, he
found that intact red blood cells were present in tube B only and they were in two different forms
as shown below:
The results are recorded in the table below:
Concentration of
Tube
solution (%)
A
0.3
Average number of different forms of
intact red blood cells
Wrinkled
Smooth
0
0
1.5
15
5
B
Note: All observations were done under the same magnification.
(a) (i)
In tube B, some red blood cells became wrinkled. How would you explain this?
(ii)
Both forms of red blood cells were observed in tube B. Give a reason for this.
(4 marks)
(b)
(c)
How could the student be sure that the red blood cells in tube B had reached equilibrium
with the surrounding solution at the time when he made the observation?
(2 marks)
Account for the absence of intact red blood cells in the mixture in tube A and the light-red
appearance of the mixture.
(4 marks)
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CE 2005_I_Q.8(b)(iv)
3. A student flooded the soil with water. As a result, the air content of the soil became very low.
Explain why this condition may lead to poor plant growth.
(3 marks)
CE 2007_I_Q.2
4. One day, when Keith and Jane walked past a fresh fruit juice shop, Keith noticed that some pears
were cut into pieces and stored in a tank of water before use.
(a)
Keith thought that the shopkeeper stored the cut pears in water in order to extract more
juice. Explain the biological principle behind Keith’s idea.
(3 marks)
(b)
Jane disagreed with Keith because she found that the shopkeeper also stored whole pears in
water tanks. Explain why this observation provides Jane with evidence to oppose Keith’s
idea.
(2 marks)
(c)
Suggest one possible hygienic (衞生) problem of storing the cut pears in water tanks.
(1 mark)
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AL 2003_II_Q.1(a)
5. The following diagram is a model illustrating the structure of a plasma membrane.
(a) Name this model. Give two features that justify such a name.
(3 marks)
(b) Explain how the nature and arrangement of molecules at W are related to the permeability
of the membrane.
(4 marks)
AL 2003_II_Q.3(a)
6. Crops that are drought resistant are economically desirable because they can survive well in
environments that have a limited water supply, whereas crops that are drought sensitive cannot.
Drought-resistant crops can produce a metabolite that can adjust the osmotic potential of the cell
sap in the root.
In drought conditions, explain how the root cells of the following plants respond osmotically.
(a) drought-sensitive plants
(2 marks)
(b) drought-resistant plants
(2 marks)
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AL 2005_II_Q.3(a)(i)(ii)(iv)
7. It has been proposed that both the mitochondrion and the chloroplast might have been
prokaryotic organisms such as an aerobic bacterium and a photosynthetic bacterium respectively.
They had been engulfed by a larger eukaryotic cell and then evolved to establish a relationship of
mutualism (互利共生) with the eukaryotic cell.
(a) Use labeled diagrams to illustrate the process of a bacterium being engulfed by a eukaryotic
cell and subsequently becoming a part of the cell.
(4 marks)
(b) Based on the process in (i), state the origin of each layer of the double envelope of the
mitochondrion and the chloroplast.
(2 marks)
(c) If the relationship between the eukaryotic cell and the engulfed bacterium is a predator-prey
one, describe how the eukaryotic cell would digest the engulfed bacterium and benefit from
it.
(4 marks)
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DSE 2014_IB_Q.7
8.
(a) The following is a schematic diagram of a cell membrane. In the spaces provided, label
membrane components X and Y.
(2 marks)
(b) The vacuoles of beetroot cells contain a red pigment which will be released from the cells
if the cell membrane and vacuole membrane are damaged. In an investigation, Gary placed
identical cylinders of beetroot tissues into four test tubes. Each tube contained the same
volume of alcohol at different concentrations. The following photograph shows the
appearance of the solutions bathing the beetroot cylinders after 30 minutes:
(i)
From the result of the above investigation, deduce which test tube contained the
highest concentration of the alcohol.
(4 marks)
(ii)
After three hours, Gary found that the colour intensity of the solutions of all the test
tubes became the same. Suggest an explanation for this.
(2 marks)
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DSE PP_2012_B_Q.2
9.
Digested food is absorbed into the epithelial cells of the villi. With reference to the structure of
the cell membrane as illustrated by the fluid mosaic model of cell membrane, explain of the
following:
(a) Fatty acids (non-polar molecules) can diffuse across the cell membrane into the epithelial
cell.
(2 marks)
(b) Amino acids (polar molecules) can be taken up from the intestinal lumen into the epithelial
cell but cannot diffuse across the epithelial cell membrane back to the lumen. (3 marks)
DSE 2015_IB_Q.5
10. The table below lists some historical developments about the discovery of the structure of cell
membrane:
(a) What is the major component noted by Overton and Langmuir?
(1 mark)
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10. (b) Gorter and Grendal proposed that the major component identified in (a) existed as a bilayer
(Bilayer Model). With reference to the observation of Langmuir, suggest how this major
component is oriented and arranged in the cell membrane. Explain your answer. (3 marks)
(c) (i)
The Bilayer Model proposed by Gorter and Grendal did not mention another major
component of the cell membrane. What is this component?
(1 mark)
(ii) With reference to the Fluid Mosaic Model, briefly describe the orientation of this
component in the cell membrane.
(2 marks)
(d) Models are often used by scientists to explain their findings. Complete the following table
to elaborate on the aspects of the nature of science involved in the use of scientific models.
(2 marks)
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ECF Saint Too Canaan College
Biology public exam exercise – Movement of substances across cell membrane answer
1.
(a)
The water potential of the cell sap of cell A is greater than that of the sucrose solution.
Water moves out of the cell by osmosis.
The vacuole shrinks in size
pulling the cytoplasm / cell membrane away from the cell wall.
1
1
1
1
(b)
The water potential of the cell sap of cell B may be the same / lower than that of the
surrounding solution.
1
(i)
Adjust the position of the slide until cell A is at the centre of the field of vision.
1
(ii)
Adjust the diaphragm / condenser to increase the illumination of the slide.
Turn the adjustment knob until the cell is in focus
1
1
(c)
(8)
2.
(a)
(i)
(ii)
(b)
(c)
The water potential of the red blood cells was higher than that of the
surrounding solution.
Water moved out of the cells.
As a result the cells shrank and became wrinkled.
1
1
1
Because the water potential of some red blood cells was higher than, while that
of others was equal to / lower than the water potential of the surrounding
solution.
1
Observe the red blood cells again after some time.
The proportion of the two forms should remain the same if they had reached
equilibrium in the previous observation.
1
1
The water potential of the red blood cells was lower than that of the surrounding
solution.
1
Water entered the cells.
The red blood cells expanded and burst
releasing the haemglobin to the solution, thus making it red.
1
1
1
(10)
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3.
When the soil became poorly aerated, plant roots would not have oxygen for respiration.
Thus they cannot absorb mineral salts from the soil
1
1
by active transport
resulting in poor plant growth.
1
(3)
4.
(a)
The water outside has a higher water potential than the cells of pears
water moves into the cells
increasing the volume of the cell content / water content of the cell.
As a result, more fruit juice can be extracted.
1
1
1
(b)
The skin of the fruit acts as barrier to water.
Little / no water movement will occur.
1
1
(c)
The water / pear may be contaminated with pathogens / lead to food poisoning.
1
(6)
5.
(a)
fluid mosaic model
fluidity : lateral movement of protein / phospholipid molecules
mosaic : protein molecules interspersed among phospholipid molecules
1
1
1
(b)
Structural-functional relationships:
W consists of 2 layers of phospholipid molecules / phospholipid bilayer.
This allows lipid soluble substances to go through as they dissolve in it.
Hydrophobic tails of the phospholipid molecules point inwards.
They form an inner hydrophobic zone; make the membrane impermeable to charged
molecules.
1
1
1
1
(7)
6.
(a)
root cells have a higher water potential than soil water
water leaves the root cells by osmosis
1
1
(b)
synthesis of the metabolite lowers the water potential / lowers the solute potential of
root cells to below that of soil water
cells will not lose water to the environment and survive / cells can still absorb water
1
1
(4)
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7.
(a)
Concept for mark award:
 Diagram showing :
- invagination of plasma membrane of the eukaryotic cell to enclose the bacterium
- closure of the invagination to form vacuole enclosing the bacterium inside the
eukaryotic cell
 Labels to indicate: bacterium, eukaryotic cell, vacuole / phagosome, plasma
membrane
e.g.
plasma membrane
vacuole / phagosome
bacterium
eukaryotic
cell
1
1
2
bacterium in vacuole
bacterium
eukaryotic cell
(b)
inner membrane comes from the bacterium
outer membrane comes from the cell membrane of the eukaryote
1
1
(c)
lysosome of eukaryotic cell fuses with vesicle containing the bacterium
digestive / hydrolytic enzymes inside the lysosome digest the bacterium
useful materials of digestion are absorbed into the cytoplasm as raw materials for
growth /
1
1
1
respiration of the eukaryotic cell
1
(10)
8.
(a)
X: * protein (1)
Y: * phospholipid (1)
(b)
(i)




(2)
tube D should have the highest concentration of alcohol (1)
the amount of pigment released to the bathing solution would be the
highest, as indicated by the highest colour intensity (1)
this is because the phospholipids of the membrane dissolve in alcohol (1)
(4)
the cell membrane and vacuole membrane of the beetroot tissue bathing in
the test tube with highest concentration of alcohol would be most damaged
(1)
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8.
(b)
(ii)

when the cell membrane and vacuole membrane are damaged, the pigment
leaks out of the vacuole by diffusion (1)

as time passes, it allows the diffusion of the red pigment in all 4 tubes to
reach an equilibrium state at which the same concentration of red (2)
pigment are found in the bathing solutions / the bathing solution becames
saturated with the same amount of red pigment in all 4 tubes, i.e. same
colour intensities (1)
(8)
9.
(a) The cell membrane is composed of a phospholipids bilayer.
Being non-polar, the fatty acids can dissolve in the phospholipids layer and diffuse
1
1
through the cell membrane.
(b) Being polar, the amino acids are repelled by the phospholipids bilayer / cannot dissolve
in the phospholipids bilayer (1) and thus cannot diffuse across the cell membrane.
3
Some proteins spanning across the phospholipids bilayer (1)
provide (hydrophilic) channels for the passage of the amino acids / act as carries for
transporting the amino acids across the membrane.
Transport of amino acids by these protein channels / carries is unidirectional. (1)
(max. 3 marks)
(5)
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