Exam (elaborations)
AQA AS/A Level Biology - Cells and Membranes Workbook (2020-21)
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A useful workbook of past paper questions on Cells and Membranes, preparing students for upcoming exams.
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Cardinal Newman CollegeCells
Q1.The diagram shows a mitochondrion.
(a) Name the parts labelled X and Y.
(i) X .............................................................
(ii) Y ..............................................................
(2)
Scientists isolated mitochondria from liver cells. They broke the cells open in an
ice-cold, isotonic solution. They then used a centrifuge to separate the cell
organelles. The diagram shows some of the steps in the process of centrifugation.
(b) Suggest which pellet, A, B or C contained the mitochondria.
(1)
(c) Explain why the solution used was
(i) ice-cold
.............................................................................................................
.............................................................................................................
(1)
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, Cardinal Newman College
(ii) isotonic.
.............................................................................................................
.............................................................................................................
.............................................................................................................
.............................................................................................................
(2)
(d) People with mitochondrial disease have mitochondria that do not function properly.
Some people with mitochondrial disease can only exercise for a short time. Explain
why a person with mitochondrial disease can only exercise for a short time.
......................................................................................................................
......................................................................................................................
......................................................................................................................
......................................................................................................................
(2)
(Total 8 marks)
Q2.A stomach ulcer is caused by damage to the cells of the stomach lining. People with
stomach ulcers often have the bacterium Helicobacter pylori in their stomachs.
A group of scientists was interested in trying to determine how infection by H. pylori
results in the formation of stomach ulcers.
The scientists grew different strains of H. pylori in liquid culture.
The table below shows the substances released by each of these strains.
Substances released by the H. pylori cells
H. pylori strain
Toxin Enzyme that neutralises acid
A
B
C
The scientists centrifuged the cultures of each strain to obtain cell-free liquids. They
added each liquid to a culture of human cells. They then recorded the amount of damage
to the human cells.
Their results are shown below. The error bars show ± 1 standard deviation.
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(a) Describe and explain how centrifuging the culture allowed the scientists to obtain a
cell-free liquid.
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
........................................................................................................................
[Extra space] ................................................................................................
........................................................................................................................
........................................................................................................................
(3)
(b) The scientists measured cell damage by measuring the activity of lysosomes.
Give one function of lysosomes.
........................................................................................................................
........................................................................................................................
........................................................................................................................
(1)
(c) H. pylori cells produce an enzyme that neutralises acid.
Suggest one advantage to the H. pylori of producing this enzyme.
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