Biology H021 - GCE
Test Name: NEW 2015 End of Membranes test
Test Duration (minutes): 42
Test Created By: Seran Bradley
Number of questions in test: 4
Candidate
forename:
Candidate
surname:
INSTRUCTIONS TO CANDIDATES
Answer all questions
Read each question carefully. Make sure you know what you have to do before starting your answer.
Write your answers to each question in the space provided. Additional paper may be used if necessary but you
must clearly show your candidate number, centre number and question number(s).
INFORMATION FOR CANDIDATES
The number of marks is given in brackets [ ] at the end of each question or part question.
Question: 1
( a ) Complete the passage below.
Membranes have a variety of functions in cells. All membranes are
permeable.
This means that they allow the passage of certain substances by processes such as active transport or
through the membrane. The cell surface membrane, also known as the .
membrane, surrounds the cytoplasm.
The cell surface membrane consists of a bilayer of
and keep it fluid, molecules of
. To stabilise the structure of the membrane
are also found in this bilayer.
[5]
( b ) Membranes contain a variety of proteins. Some of these proteins are combined with carbohydrates to form
glycoproteins.
Describe the functions of glycoproteins in the cell surface membrane.
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[5]
[Total: 10]
Question: 2
( a ) A student wanted to observe some red blood cells under the microscope. The student placed a small sample of blood
onto a microscope slide and added a drop of distilled water. When viewed at high power, the student observed that the
red blood cells had burst.
In a similar procedure using plant epidermis, the student observed that the plant cells did not burst.
( i ) Explain these observations.
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[5]
(ii) Suggest how the student could modify the procedure to observe red blood cells without them bursting.
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[1]
( b) Oxygen enters red blood cells as they pass through the capillaries in the lungs.
Name the mechanism by which oxygen enters the red blood cells.
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[1]
(c) The cells in the epidermis of a plant root are specialised to absorb minerals from the surrounding soil.
State the process by which root epidermal cells absorb minerals from the soil and describe how these cells are specialised
to achieve absorption.
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[3]
[Total: 10]
Question: 3
(a) (i) Name the process by which water leaves a cell.
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[1]
(ii) Describe the routes that water molecules take through the cell surface membrane.
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[2]
A student carried out an investigation to determine the effects of different sucrose concentrations on cells from pieces of
onion epidermis.
• Strips of epidermis were taken from an onion.
• Separate pieces of epidermis were placed into water and a range of sucrose solutions.
• The pieces of epidermis were left for 30 minutes before being removed.
• The pieces of epidermis were then viewed at high power under the microscope.
The student counted 100 cells from each piece of epidermis. The student noted how many cells had become plasmolysed.
The results are shown in Table 6.1.
( b) None of the onion epidermis cells this student observed had burst when left in pure water.
Explain why plant cells do not burst when they are left in pure water.
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[2]
(c) (i) The water potential of the onion epidermis cells can be assumed to be the same as the water potential of a
solution that causes 50% plasmolysis.
Use the information in Table 6.1 to estimate the water potential inside these onion epidermis cells.
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[1]
(ii) Suggest how the student could construct and use a graph to obtain a better estimate of the water potential.
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[2]
( d ) Suggest how the student could modify the procedure to make the results more reliable and accurate.
reliable
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accurate
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[4]
[Total: 12]
Question: 4
The cell surface membrane allows different substances to enter and leave the cell.
( a ) List three components of a cell surface membrane.
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[3]
(b) (i) Explain what is meant by the term active transport.
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[2]
(ii) State two examples of active transport in cells.
For each example, you should name the substance that is transported and the cell involved.
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[2]
( c ) In addition to active transport, substances can pass through cell surface membranes by:
• diffusion
• facilitated diffusion
• osmosis
• bulk transport (endocytosis / exocytosis)
For each example described in Table 2.1 below, state how the substance crosses the cell surface membrane. The first one
has been done for you.
Table 2.1
example
release of enzymes into the gut
mechanism of movement across cell surface
membrane
bulk transport
a plant cell taking up water
calcium ions entering a nerve cell down a
concentration gradient
oxygen entering a red blood cell
[3]
[Total: 10]