BIOLOGY
19..
12: CELL MEMBRANE TRANSPORT REVIEW
a) Identify the process shown in the diagram
beside. (1 mark)
• active transport
b) Give one example in which this process is used in
the body. (1 mark)
• muscle contraction for movement
• signals sent along nerve cells
c) Describe the function of the molecule
represented by P PP : (1 mark)
• provides the energy for this process to
occur
d) What is the function of molecule X? (1 mark)
• transport sodium ion out of the cell
20.
Four thistle tubes are partially filled with salt solutions of various concentrations and sealed with
membranes that are permeable to water but
impermeable to salt. Each thistle tube is then
placed in a beaker containing a 2% salt solution.
The experiment is left for two hours. The
diagrams show the appearance of each thistle
tube at the start of the experiment and at the
end of two hours. For each tube, explain what
caused the differences in levels observed after
two hours. Give reasons to support your answer.
(4 marks)
salt solutions of the beakers as compared to the thistle tube are:
I is hypertonic therefore water moves out of the thistle tube by osmosis
II is hypotonic therefore water moves into the thistle tube by osmosis
III is also hypotonic therefore water moves into the thistle tube by osmosis but III is also
hypotonic compared to beaker II because less water moves in as compared to beaker II
IV is isotonic therefore there is movement of water back and forth along the membrane but
they are equal to each other therefore the thistle tube does not gain any water
21.
Two identical red blood cell samples were prepared for an experiment. The samples were
placed in two different solutions and the percent change in mass was recorded and graphed
over an eight hour period as shown below.
a) Account for the change in mass of the cells in Solution A during the first four hours.
(2 marks)
•
Solution is hypotonic as compared to the cell therefore water moves into the cell by
osmosis (from high concentration of water to low concentration of water)
b) What happened to the cells in Solution A after four hours? (1 mark)
• The cell bursts (cell lysis)
c) Give one reason for the results obtained from the cells placed in Solution B between three
and eight hours. (1 mark)
•
after 3 hours the cell is isotonic (concentrations of solute and water are equal) to
solution B