Practical Skills, Apparatus and Technique Booklet
Within the booklet you have:
1. The apparatus and techniques table for AQA A level. This shows all the apparatus or
techniques that they could ask you about within the exam.
2. The required practicals list of AQA. This also shows you which apparatus and techniques link
to each required practical and therefore what could be assessed in the exam for the
practicals.
3. 124 marks worth of past paper practical techniques questions
4. The mark scheme for the exam questions
Page 1 of 49
Practical Technique Exam
Questions
Time:
154 minutes
Marks:
124 marks
Name:
________________________
Class:
________________________
Date:
________________________
Comments:
Page 2 of 49
Q1.
Yeast cells can respire aerobically or anaerobically. A student used the apparatus shown
in Figure 1 to measure the rate of respiration in yeast.
She:
•
•
positioned the flask in a water bath so that the yeast culture reached a constant
temperature
then left the apparatus for one hour before starting her investigation.
Figure 1
(a)
Suggest one reason why it was important that the student left the apparatus for one
hour after the yeast culture reached a constant temperature.
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(1)
(b)
During her investigation, the coloured liquid moved to the right.
Explain why it moved to the right.
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(2)
(c)
The student found that the coloured liquid moved 1.5 cm in 24 hours. The diameter
of the lumen (hole) of the capillary tubing was 1 mm.
The volume of a capillary tubing is given by πr2l, where π is 3.14 and l = length.
Calculate the volume of gas produced in cm3 hour–1.
Show your working.
Answer = ____________________ cm3 hour–1
(2)
Figure 2 shows a typical population growth curve for yeast under laboratory conditions.
Figure 2
(d)
Explain why a log scale is used to record the number of cells.
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(1)
(e)
Many yeast cells die during the death phase.
Suggest one reason why.
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(1)
(f)
The following equation can be used to make predictions of the growth in the
population of yeast cells under ideal laboratory conditions.
Xt = X0 ert
Xt = the population after a certain time
X0 = the population at the start
e = 2.72 (base of natural logarithm)
r = growth rate
t = time period in hours over which r applies
A population of 2000 yeast cells was left for 10 hours.
The value for the growth rate was 0.5
Assuming no yeast cells died, calculate the predicted size of the population after 10
hours. Show your working.
Answer = ____________________
(2)
(Total 9 marks)
Q2.
A student investigated the effect of three types of disinfectant on the growth of
Lactobacillus bacteria.
During the investigation, the student:
•
boiled the agar before pouring the agar plates
•
transferred 0.5 cm3 of a diluted liquid culture of Lactobacillus onto each agar plate
•
left some agar plates as controls
•
added to other agar plates different concentrations of the disinfectants as shown in
the table in part (a).
After 2 days, she counted the number of colonies of bacteria on each agar plate.
(a)
Explain the purpose of:
boiling the agar ______________________________________________________
Page 5 of 49
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transferring the same volume of liquid culture onto each agar plate.
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(2)
The three disinfectants used by the student were Lysol, propan-2-ol and ammonia.
The table shows the student’s results.
Concentration
of disinfectant /
arbitrary units
Number of colonies of bacteria
Lysol
Propan-2-ol
Ammonia
0
300
300
300
5
0
290
300
10
0
195
295
15
0
0
275
20
0
0
240
The liquid culture the student transferred was diluted by 1 in 10 000 (10−4).
(b)
Use information in this question to calculate how many bacteria were present in
1 cm3 of undiluted liquid culture.
Answer = ____________________
(2)
(c)
The student concluded that the minimum concentration of propan-2-ol needed to
stop the growth of Lactobacillus was 15 units. This conclusion is incorrect.
Describe how you could obtain a more accurate estimate of the minimum
concentration of propan-2-ol needed to stop the growth of this species of bacterium.
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(2)
(Total 6 marks)
Q3.
(a)
Describe how you would use cell fractionation techniques to obtain a sample of
chloroplasts from leaf tissue. Do not include in your answer information about any
solutions.
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(3)
(b)
The table shows features of a mitochondrion and a chloroplast. Complete the table
with ticks where a feature is present.
Feature
Mitochondrion
Chloroplast
Double outer
membrane
Starch grains
Diffusion of oxygen into
the organelle
(3)
(c)
Give the function of a mitochondrion.
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(1)
(d)
Scientists investigated the effect of an exercise programme on the number and size
of mitochondria in skeletal muscle. They took samples of muscle from a large
number of volunteers before and after the exercise programme. From each sample,
they cut thin sections and used these to determine the mean number of
mitochondria per μm2 and the mean area of inner mitochondrial membranes.
Their results are shown in Graph 1 and Graph 2.
What do the data in Graph 1 and Graph 2 suggest about the effect of the exercise
programme on mitochondria?
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(2)
(Total 9 marks)
Q4.
The figure below shows the apparatus used for measuring the rate of oxygen
consumption in aerobic respiration by seeds.
Page 8 of 49
(a)
For the first 10 minutes, the tap attached to tube A was left open and the syringe
from tube B was removed.
Suggest three reasons why the apparatus was left for 10 minutes.
1. _________________________________________________________________
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2. _________________________________________________________________
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3. _________________________________________________________________
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(3)
(b)
Suggest and explain why the chosen temperature was 20 °C for this experiment.
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(2)
After 10 minutes, the tap attached to tube A was closed and the syringe was attached to
tube B. Every minute, the syringe plunger was moved until the levels in the U-tube were
the same. The reading on the syringe volume scale was then recorded.
The results are shown in the table below.
Page 9 of 49
(c)
Time / minutes
Reading on syringe
volume scale / cm3
0
0.84
1
0.81
2
0.79
3
0.76
4
0.73
5
0.70
6
0.68
7
0.66
8
0.63
9
0.62
10
0.58
During the experiment, the coloured liquid in the tubing moved towards tube B.
Explain what caused this.
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(3)
(d)
The mass of the seeds was 1.6 g. Use the information in the table above to
calculate the rate of oxygen consumption in cm3 g–1 hour–1 by the seeds.
Show your working.
Rate = ____________________ cm3 g–1 hour–1
(2)
(Total 10 marks)
Page 10 of 49
Q5.
A student investigated the effect of ethanol, hydrochloric acid and temperature on the loss
of red pigment from beetroot cells.
During the procedure, the student:
•
•
•
•
•
•
•
•
•
•
added 10 cm3 water into one test tube
added 10 cm3 ethanol into a second test tube
added 10 cm3 hydrochloric acid into a third test tube
put the three tubes into a 25 °C water bath
cut four cylinders of tissue from a beetroot
put a cylinder into each tube and fitted bungs
added 10 cm3 water into a fourth test tube and put this tube into a 70 °C water bath
placed the fourth cylinder into this tube and fitted a bung
later removed the cylinders from the tubes
estimated the intensity of red pigment in each solution by eyesight.
(a)
Give one way in which the student could ensure the first three beetroot cylinders
were kept at 25 °C throughout her experiment.
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(1)
(b)
Give two variables that the student did not control in her procedure.
1 _________________________________________________________________
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2 _________________________________________________________________
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(2)
(c)
The student used a measuring cylinder to obtain 10 cm3 of each solution.
Figure 1 shows some of the scale graduations on the side of this measuring
cylinder.
Figure 1
What is the uncertainty of taking a reading of 10 cm3 with this measuring cylinder?
Suggest how you could reduce the uncertainty calculated.
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Uncertainty ± _______________ cm3
Reducing uncertainty _________________________________________________
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(2)
A different student used the same procedure and she controlled all variables
appropriately. Her results are shown in Figure 2.
Figure 2
(d)
Using Figure 2, what can you conclude about the damage caused to beetroot cells
by water, ethanol, hydrochloric acid and different temperatures?
Provide explanations for your conclusions.
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(4)
(Total 9 marks)
Q6.
The diagram shows the structure of two α-glucose molecules.
(a)
On the diagram, draw a box around one chemical group in each glucose molecule
used to form a glycosidic bond.
(1)
(b)
A precipitate is produced in a positive result for reducing sugar in a Benedict’s test.
A precipitate is solid matter suspended in solution.
A student carried out the Benedict’s test. Suggest a method, other than using a
colorimeter, that this student could use to measure the quantity of reducing sugar in
a solution.
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(2)
Page 13 of 49
In an investigation, a student wanted to identify the solutions in two beakers, A and B.
She knew one beaker contained maltose solution and the other beaker contained glucose
solution. Both solutions had the same concentration.
She did two separate biochemical tests on a sample from each beaker.
Test 1 – used Benedict’s solution to test for reducing sugar.
Test 2 – added the enzyme maltase, heated the mixture at 30 °C for 5 minutes, and then
used Benedict’s solution to test for reducing sugar.
Maltose is hydrolysed by maltase.
The student’s results are shown in the table below.
Colour of solution after testing
with Benedict’s solution
(c)
Beaker
Test 1
Test 2
A
red
red
B
red
dark red
Explain the results for beakers A and B in the table.
Beaker A __________________________________________________________
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Beaker B __________________________________________________________
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(2)
(d)
Use of a colorimeter in this investigation would improve the repeatability of the
student’s results.
Give one reason why.
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(1)
In Test 1, the student used a measuring cylinder to measure 15 cm3 of solution from a
Page 14 of 49
beaker. The measuring cylinder gives a volume with an uncertainty of ±1 cm3. She used a
graduated syringe to measure 5.0 cm3 of Benedict’s solution. The graduated syringe gives
a volume with an uncertainty of ± 0.5 cm3. She mixed these volumes of liquid to do the
biochemical test.
(e)
Calculate the percentage error for the measurements used to obtain a 20 cm3
mixture of the solution from the beaker and Benedict’s solution. Show your working.
(2)
Answer = _____________________________%
(Total 8 marks)
Q7.
(a)
A student used a dilution series to investigate the number of cells present in a liquid
culture of bacteria.
Describe how he made a 1 in 10 dilution and then used this to make a 1 in 1000
dilution of the original liquid culture of bacteria.
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(3)
(b)
Using an optical microscope, the student determined there were 15 cells in 0.004
mm3 of the 1 in 1000 dilution of the culture.
Page 15 of 49
Calculate the number of cells in 1 cm3 of undiluted liquid culture.
Answer = ____________________ Number of cells
(2)
(c)
The student looked at cells in the 1 in 10 dilution during his preliminary work. He
decided not to use this dilution to determine the number of cells in the undiluted
liquid culture.
Suggest an explanation for the student’s decision.
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(2)
(d)
On some farms, animals are routinely given antibiotics in their food.
Scientists investigated whether these farm animals had antibiotic-resistant bacteria
in their intestines. They tested the bacteria for resistance to two antibiotics,
tetracycline and streptomycin.
Their results are shown in the table.
Antibiotic
Percentage of
antibiotic-resistant
bacteria
Tetracycline
29
Streptomycin
13
Suggest and explain one reason why bacteria resistant to tetracycline are more
common than bacteria resistant to streptomycin in these farm animals.
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(2)
(e)
In recent years, these farm animals have not been given tetracycline in their food.
Despite this, the percentage of bacteria resistant to tetracycline has remained
constant.
Suggest one reason why.
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(1)
(Total 10 marks)
Q8.
A student investigated the effect of surface area on osmosis in cubes of potato.
•
•
•
•
He cut two cubes of potato tissue, each with sides of 35 mm in length.
He put one cube into a concentrated sucrose solution.
He cut the other cube into eight equal-sized smaller cubes and put them into a
sucrose solution of the same concentration as the solution used for the large cube.
He recorded the masses of the cubes at intervals.
His results are shown in the graph.
Page 17 of 49
(a)
Describe the method the student would have used to obtain the results in the graph.
Start after all of the cubes of potato have been cut. Also consider variables he
should have controlled.
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Page 18 of 49
(3)
(b)
The loss in mass shown in the graph is due to osmosis. The rate of osmosis
between 0 and 40 minutes is faster in B (the eight small cubes) than in A (single
large cube).
Is the rate of osmosis per mm2 per minute different between A and B during this
time?
Use appropriate calculations to support your answer.
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(3)
(Total 6 marks)
Q9.
(a)
A student prepared a stained squash of cells from the tip of an onion root and
observed it using an optical microscope.
During the preparation of the slide, he:
•
•
•
•
cut the first 5 mm from the tip of an onion root and placed it on a glass slide
covered this tip with a drop of stain solution and a cover slip
warmed the glass slide
pressed down firmly on the cover slip.
He identified and counted nuclei in different stages of the cell cycle.
Explain why the student:
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1. used only the first 5 mm from the tip of an onion root.
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2. pressed down firmly on the cover slip.
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(2)
Figure 1 shows the cells the student saw in one field of view. He used this field of view to
calculate the length of time these onion cells spent in anaphase of mitosis.
Figure 1
(b)
Scientists have found the mean length of time spent by onion cells in anaphase of
mitosis is 105 minutes. They also found the cell cycle of cells in the onion root
shown in Figure 1 takes 1080 minutes.
32 whole cells are shown in Figure 1.
Page 20 of 49
Use this information and Figure 1 to calculate the length of time the cells of this
onion root are in anaphase and then calculate the percentage difference between
your answer and the mean length of time found by the scientists.
Show your working.
Answer = ____________________ %
(2)
(c)
Tick (✓) the name given to the division of cytoplasm during the cell cycle.
A
Binary fission
B
Cytokinesis
C
Phagocytosis
D
Segregation
(1)
(d)
Describe and explain what the student should have done when counting cells to
make sure that the mitotic index he obtained for this root tip was accurate.
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(2)
(e)
A scientist treated growing tips of onion roots with a chemical that stops roots
growing. After 24 hours, he prepared a stained squash of these root tips.
Page 21 of 49
Figure 2 is a drawing showing the chromosomes in a single cell observed in the
squash of one of these root tips in anaphase. This cell was typical of other cells in
anaphase in these root tips.
Figure 2
Use all of this information to suggest how the chemical stops the growth of roots.
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(3)
(Total 10 marks)
Q10.
A student investigated the effects of indoleacetic acid (IAA) on the growth of oat seedlings
(young plants).
The student:
Page 22 of 49
•
•
•
•
•
•
•
removed the shoot tip from each seedling and cut out a 10 mm length of shoot
placed 10 lengths of shoot into each of 5 Petri dishes
added to each Petri dish an identical volume of 5% glucose solution
added to each Petri dish 40 cm3 of a different concentration of IAA solution
left the Petri dishes at 20 °C in the dark with their lids on for 5 days
removed the shoots after 5 days and measured them
determined the mean change in length of shoot at each concentration of IAA.
Table 1 shows her results.
Table 1
(a)
IAA concentration
added to Petri dish /
parts per million
10−5
10−3
10−1
1
10
Mean change in
length of shoot / mm
0.0
0.1
1.3
2.4
3.1
Explain why the student removed the shoot tip from each seedling.
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(2)
(b)
Explain why the student added glucose solution to each Petri dish.
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Page 23 of 49
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(2)
(c)
Explain why the lids were kept on the Petri dishes.
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(2)
(d)
Describe and explain the results shown in Table 1 above and suggest how the
results might have differed if lengths of root had been used.
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(3)
(e)
The student produced the different concentrations of IAA using a stock 1 g dm−3
solution of IAA (1 g dm−3 = 1 part per thousand) and distilled water.
Complete Table 2 with the volumes of stock IAA solution and distilled water required
to produce 40 cm3 of 10 ppm (parts per million) IAA solution.
Table 2
Concentration of IAA
solution / parts per
million
Volume of stock
IAA solution / cm3
Volume of distilled
water / cm3
10
(1)
(Total 10 marks)
Page 24 of 49
Q11.
A student used the apparatus shown in Figure 1 and a digital balance to determine the
rate of water movement in a celery stalk in grams per hour per group of xylem vessels.
Figure 1
(a)
The student measured the time taken for water movement.
Give two other measurements he made to calculate the rate of water movement.
1 _________________________________________________________________
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2 _________________________________________________________________
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(2)
(b)
Give the reason for adding a layer of oil to the water in the beaker.
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(1)
(c)
A different student used coloured water to investigate the movement of water in leaf
stalks of celery.
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During the procedure she:
•
•
•
•
cut equal lengths of stalk from each plant
put the cut end of each stalk into coloured water
left these stalks to take up the coloured water for 20 minutes
used a sharp scalpel to cut slices from the stalks at 1 mm intervals until she
reached a slice with no coloured water.
Figure 2 shows a slice of leaf stalk with coloured water inside groups of xylem
vessels.
Figure 2
Explain why coloured water moved up the stalks.
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(3)
(d)
The student used a sharp scalpel to cut the celery. Describe how she should ensure
she handled the scalpel safely during this procedure.
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(2)
The student measured the distance the coloured water had travelled in eight celery stalks.
Her results are shown in the table.
Distance / mm
70
(e)
35
40
35
30
80
42
44
The student had to choose whether to summarise her measurements by calculating
the mean, the median or the mode.
Circle the most appropriate measure for this set of measurements.
Give a reason for your choice and find the value using the measurements from all
eight stalks.
Mean*
Median*
Mode*
*circle one word.
Reason: ___________________________________________________________
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Calculation:
Answer = ______________________________
(2)
(Total 10 marks)
Q12.
The water potential of leaf cells is affected by the water content of the soil.
Scientists grew sunflower plants. They supplied different plants with different volumes of
water.
After two days, they determined the water potential in the leaf cells by using an instrument
that gave a voltage reading.
The scientists generated a calibration curve to convert the voltage readings to water
potential.
Figure 1 shows their calibration curve.
Figure 1
Page 27 of 49
(a)
The scientists needed solutions of known water potential to generate their calibration
curve.
Table 1 shows how to make a sodium chloride solution with a water potential of
−1.95 MPa
Complete Table 1 by giving all headings, units and volumes required to make
20 cm3 of this sodium chloride solution.
Table 1
Water
potential /
MPa
Concentration of
sodium chloride
solution / mol dm−3
Volume of
1 mol dm−3 sodium
chloride solution /
________________
_________________ ___________/ ____
−1.95
0.04
_________________ ________________
(2)
Table 2 shows some of the concentrations of sodium chloride solution the scientists used
and the water potential of each solution.
Table 2
Concentration of Water potential
sodium chloride
/ MPa
solution / mol dm−3
0.04
−1.95
0.10
−4.87
0.12
−5.84
(b)
There is a linear relationship between the water potential and the concentration of
sodium chloride solution.
Use the data in Table 2 to calculate the concentration of sodium chloride solution
with a water potential of −3.41 MPa
Page 28 of 49
Answer = ___________________________ mol dm−3
(2)
In addition to determining the water potential in the leaf cells, the scientists measured the
growth of the leaves.
They recorded leaf growth as a percentage increase of the original leaf area.
Their results are shown in Figure 2.
Figure 2
(c)
One leaf with an original area of 60 cm2 gave a voltage reading of −7 µV
Use Figure 1 and Figure 2 to calculate by how much this leaf increased in area.
Give your answer in cm2
Answer = _________________________ cm2
(2)
(d)
Sunflowers are not xerophytic plants. The scientists repeated the experiment with
xerophytic plants.
Suggest and explain one way the leaf growth of xerophytic plants would be different
from the leaf growth of sunflowers in Figure 2.
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Page 29 of 49
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(2)
(e)
Use your knowledge of gas exchange in leaves to explain why plants grown in soil
with very little water grow only slowly.
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(2)
(Total 10 marks)
Q13.
A scientist identified and counted the invertebrate species present in samples taken at two
sites in a river. The scientist also measured the rate of water flow at each site.
His results are shown in Table 1 and Table 2.
Table 1
Invertebrate species
Site 1
Site 2
Anglers' Curse mayfly
17
5
Flat-headed mayfly
6
8
Slate Drake mayfly
0
6
Water beetle
12
13
Midge fly
13
13
Total number caught
48
45
Site 1
Site 2
Table 2
Index of diversity
Page 30 of 49
4.7
Rate of water flow / cm s–1
(a)
1-14
30-60
Complete Table 2 by calculating the index of diversity (d) at Site 1.
Index of diversity (d) = _______________________
(1)
(b)
Explain why it is more useful to calculate an index of diversity than to record species
richness.
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(2)
(c)
Suggest how the scientist measured the rate of water flow in the river.
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(1)
(d)
Use information in Table 1 and Table 2 to suggest and explain a reason for the
difference in the numbers of Slate Drake mayfly at these sites in this river.
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(2)
(e)
It was important that the sampling procedure was standardised when collecting the
Slate Drake mayflies from the two sites.
Give one way in which the sampling procedure could be standardised.
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(1)
(Total 7 marks)
Q14.
(a)
Explain how the active site of an enzyme causes a high rate of reaction.
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(3)
The action of the enzyme catalase is shown below.
A student investigated the effect of hydrogen peroxide concentration on the rate of this
reaction. He used catalase from potato tissue.
The student:
•
put five potato chips in a flask
•
added 20 cm3 of 0.5 mol dm–3 hydrogen peroxide solution to the flask
•
measured the time in seconds for production of 10 cm3 of oxygen gas
•
repeated this procedure with four different concentrations of hydrogen
peroxide solution.
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His results are shown in the table.
(b)
Hydrogen peroxide
concentration / mol dm–3
Time for production
of 10 cm3 of oxygen
gas / seconds
0.5
18
1.0
10
1.5
7
2.0
6
2.5
6
Rate of reaction /
arbitrary units
Other than those stated, give one factor the student would have controlled in his
investigation.
___________________________________________________________________
___________________________________________________________________
(1)
(c)
The student gave the maximum rate of reaction a value of 1.0 arbitrary units.
Complete the table above by calculating the rate of reaction in arbitrary units at each
hydrogen peroxide concentration. Record the rates using an appropriate number of
significant figures.
(2)
(d)
Plot a suitable graph of your processed data shown in the table.
Page 33 of 49
(3)
(e)
Suggest a change the student could make to his procedure so that 10 cm3 of oxygen
would be produced in less than 6 seconds.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(1)
(Total 10 marks)
Page 34 of 49
Mark schemes
Q1.
(a)
(So the) oxygen is used/absorbed/respired;
1
(b)
1.
Anaerobic respiration produces carbon dioxide;
2.
Increase in pressure/volume (of gas);
Reference to either volume or pressure required for the mark
2
(c)
1.
Correct answer in range of
4.9 × 10–4 to 4.91 × 10–4 = 2 marks;;
Accept any equivalent mathematical representation of this
answer
2.
Incorrect answer buts shows division by 24 = 1 mark
OR
Incorrect answer but shows a number from 1175 to 1178 (ignore position of
decimal point, standard form and any numbers that follow) = 1 mark;
OR
Incorrect answer but show the number 49 (ignore position of decimal point,
standard form and any numbers after 49) = 1 mark;
2
(d)
Large range/difference/increase in numbers;
Accept reference to exponential (increase)
Ignore if the answer only refers to numbers being high
Ignore to ‘fit on the scale’
1
(e)
Decrease/no glucose/substrate
OR
Increase in ethanol/carbon dioxide/acidity;
Accept decrease/no oxygen as Figure 2 is not linked to
Figure 1.
Accept competition for glucose/oxygen.
Accept any named sugar
Accept decrease in pH
Accept increase in toxins
Ignore food/nutrients
1
(f)
1.
Correct answer of 298000 or 297766 or 297765.59 or 296826 = 2 marks;;
Accept: any equivalent answer with appropriate rounding
e.g. 2.98 × 105,
29.78 × 104 etc.
2.
Incorrect answer but working shows 2000 × 2.72 = 1 mark;
OR
Incorrect answer but working shows 2.720.5 × 10 / 2.725 / e0.5 × 10 / = 1 mark
2
Page 35 of 49
[9]
Q2.
(a)
1.
2.
So no contamination / other bacteria;
So same number of bacteria transferred to allow
comparison;
1.
Accept sterilisation / kills all (bacteria)
2.
Allow amount / concentration for number
2
(b)
6 000 000
OR
6 × 10 6;
1 mark for 3 000 000
OR
3 × 10 6
Allow 1 mark for 600 (in 1cm 3 of diluted culture)
2
(c)
1.
2.
(Several) values between 10 and 15 (units);
Repetitions of each;
1.
Accept descriptions of this
Ignore repeat the investigation / repeat at 10 and 15 units.
2
[6]
Q3.
(a)
1.
2.
3.
Macerate / homogenise / blend / break tissues / cells (in solution);
Centrifuge;
At different / increasing speeds until chloroplast fraction obtained;
1.
Accept any suitable method to break tissues / cells /
release organelles
2. and 3. Allow ‘perform differential centrifugation until
chloroplasts obtained.’ for 2 marks
3
(b)
Feature
Double outer
membrane
Mitochondrion
Chloroplast
✔
✔
✔
Starch grains
Diffusion of
oxygen into the
organelle
✔
1 mark for each correct row
Crosses = blank space
3
(c)
The site of aerobic respiration (reactions)
OR
Page 36 of 49
ATP is made / ADP is phosphorylated;
Reject ‘energy is produced’
1
(d)
1.
2.
Training made no difference to number (of mitochondria per μm2);
Training led to an increase in the area (of inner mitochondrial
membrane);
1.
Accept Graph 1 as mean number of mitochondria per
μm 2
2.
Accept Graph 2 as area of inner mitochondrial
membrane
2
[9]
Q4.
(a)
1.
Equilibrium reached.
Accept equilibrate
2.
3.
Allow for expansion / pressure change in apparatus;
Allow respiration rate of seeds to stabilise.
Ignore seeds acclimatise
3
(b)
1.
2.
Optimum temperature / temperature for normal growth of seeds;
(Optimum temperature) for enzymes involved in respiration.
2
(c)
1.
2.
3.
Oxygen taken up / used by seeds;
CO2 given out is absorbed by KOH (solution);
Volume / pressure (in B) decreases.
3
(d)
0.975 / 0.98.
If incorrect,
0.26 × 6 / or incorrect numbers divided by 1.6 for 1 mark
2
[10]
Q5.
(a)
Measure temperature (in tube) at intervals and use appropriate corrective measure
(if temperature has fluctuated);
Accept use thermometer/probe/ equivalent device for
measure temperature
1
(b)
1.
Length and diameter
OR
Surface area
OR
Volume
Page 37 of 49
OR
Mass/weight (of cylinders);
Ignore shape/size
2.
Time in solution;
Ignore ‘time’ if unqualified
2
(c)
1.
1;
2.
Use instrument with closer/finer/smaller intervals/graduations/scale;
Accept correct numerical figure, eg <2 (cm3)
Ignore ‘higher resolution’
2
(d)
1.
Water/25oC caused no damage/no pigment release (in E);
Accept no colour/intensity change for ‘pigment’
Accept ‘high temperature’ for 70°C
Accept description of 'pigment release' for 'damage'
2.
(Damage to) cell(-surface) membrane;
Accept description of membrane, eg phospholipid
bilayer/bilayer
3.
Ethanol/acid caused some/similar/identical damage
OR
70oC caused most damage;
Accept description of ‘pigment release’ for ‘damage’
4.
(By) ethanol dissolving phospholipid bilayer
OR
(By acid) altering membrane protein;
Accept carrier OR channel OR intrinsic OR extrinsic protein
for membrane protein
5.
(By) 70oC denaturing/altering membrane protein
OR
(By) 70oC increasing fluidity/permeability of membrane;
Accept carrier OR channel OR intrinsic OR extrinsic protein
for membrane protein
Ignore reference to enzymes unless qualified as membrane
bound
4 max
[9]
Q6.
(a)
Page 38 of 49
Accept a box drawn around any OH and H from another OH
OR
Accept one box around two OHs
1
(b)
1.
Filter and dry (the precipitate);
Accept: correct reference to evaporation after filtration
2.
Find mass/weight;
2
(c)
1.
A = glucose and B = maltose;
2.
Because more sugar/precipitate after hydrolysis/maltase action;
Accept ‘higher concentration of sugar’ for ‘more sugar’
Accept ‘break down’ for hydrolysis
2
(d)
1.
Quantitative
OR
(Colour change is) subjective;
Accept: accurate/precise
2.
Standardises (the) method;
1 max
(e)
16.67 − 17 = 2 marks;
(cumulative percentage error of both measuring vessels)
If incorrect final answer, accept for 1 mark:
0.167 − 0.17 (not a percentage)
OR
evidence of
(correct understanding, but not calculated)
Ignore: ± (plus or minus) in answer
2
[8]
Q7.
(a)
1.
Add 1 part (bacteria) culture to 9 parts (sterile) liquid (to make 10–1 dilution);
Accept water / nutrient / broth for liquid
2.
Mix (well);
Page 39 of 49
Accept stir
3.
Repeat using 9 parts fresh (sterile) liquid and 1 part of 10–1 and 10–2 dilutions
to make 10–3 dilution;
OR
Add 1 part 10–1 (suspension) to 99 parts (sterile) liquid (to make 10–3 dilution);
Accept water / nutrient / broth for liquid
Reject 1 part (undiluted) culture added to 999 parts liquid
3
(b)
3.75 × 109 / 3 750 000 000;;
Accept for 1 mark: 3750 000 / 3.75 × 106 (cells per mm3)
OR
3.75 × 1012 (wrong volume conversion)
OR
3750 (cells per mm3 of diluted culture)
OR
Evidence of using correct dilution conversion and correct
volume conversion, i.e., × 1000 and × 1000
2
(c)
1.
Count unlikely to be accurate / repeatable / reproducible / reliable;
2.
Because too many cells;
OR
Because cells overlapping / not spread out;
2
(d)
1.
Tetracycline used more often / in higher doses;
2.
Resistant bacteria more likely to (survive and reproduce and) pass on
allele/gene for (tetracycline) resistance;
OR
3.
More / higher frequency of mutations (for tetracycline resistance);
Reject reference to mutation being caused by use of
antibiotic
4.
(so) gene passed on to more bacteria;
OR
5.
Tetracycline used over longer time period;
6.
More time for (chance) mutation to occur / for selection to occur;
Ignore reference to resistant animals
Ignore reference to immunity
2
(e)
No selection against resistant bacteria / resistance gene/allele;
OR
Bacteria pass on (resistance) gene / allele when they reproduce;
OR
Bacteria resistant to tetracycline are passed on from one generation of farm animals
to the next (probably via faeces);
OR
Page 40 of 49
Environment does not change, so stabilising selection occurs;
Accept no selection to get rid of it
Reject reference to mitosis or immunity
1
[10]
Q8.
(a)
1.
Method to ensure all cut surfaces of the eight cubes are exposed to the
sucrose solution;
Credit valid method descriptions to fulfil mp1, 2 and 3 (no
explanation is required).
2.
Method of controlling temperature;
Accept ‘at room temperature’ for method
3.
Method of drying cubes before measuring;
4.
Measure mass of cubes at stated time intervals;
Accept time intervals between every 5 minutes with
maximum of every 40 minutes.
Accept ‘weigh the cubes at stated time intervals’
3 max
(b)
Yes or No (no mark)
Calculation of rate per mm2 for both sets of data, accept answers in the range
1.6 × 10–5 to 1.8 × 10–5 and
1.5 × 10–5 to 1.6 × 10–5;;; Both correct = 3
One correct = 2
Neither correct – look below for max 2
Allow 1 mark for calculation of surface area of two (sets of) cubes 7350 (mm2) and
14700 (mm2)
Allow 1 mark for calculation of both rates of osmosis shown in first 40 minutes –
between 0.12 and 0.13 and between 0.22 and 0.23
If surface area and/or rate of osmosis is incorrect then, allow 1 mark for (their)
calculated rate divided by (their) calculated surface area
Accept answers not given in standard form or to any number
of significant figures ≥2sf as long as rounding correct.
3 max
[6]
Q9.
(a)
1.
Where dividing cells are found / mitosis occurs;
OR
No dividing cells / mitosis in tissue further away / more than 5 mm from tip;
OR
To get (soft) tissue that will squash;
OR
Length that will fit under cover slip;
Page 41 of 49
Accept most dividing cells
2.
Single / thin layer of cells / spread out cells so light passes through (making
cells / nuclei visible);
Accept thin layer of tissue
Ignore to see cells clearly
2
(b)
3.57 / 3.6 / 3.7 / 3.71 / 3.8 (%);;
If the answer includes additional decimal places, award the
marks if it would round to a correct answer
There are 3 cells in anaphase
Accept for 1 mark, 101.25 / 101 (students estimate in
minutes)
OR
3.75 (difference between scientist estimate and student’s
estimate in minutes)
Ignore plus or minus signs
2
(c)
Cytokinesis;
1
(d)
Description;
Explanation;
E.g,
1.
Examine large number of fields of view / many cells;
Mark as pairs only
Accept large number / 20 or more for many
2.
To ensure representative sample;
Accept typical / reliable
OR
3.
Repeat count;
4.
To ensure figures are correct;
OR
5.
Method to deal with part cells shown at edge /count only whole cells;
6.
To standardise counting;
2 max
(e)
1.
Stops anaphase / cell division / mitosis;
Accept prevents telophase / cytokinesis
2.
(By) stopping / disrupting / spindle fibres forming / attaching / pulling;
Ignore affects anaphase
3.
Preventing separation of (sister) chromatids;
Ignore chromosomes separate / split
Page 42 of 49
Accept chromatids split
4.
(So) no new cells added (to root tip);
3 max
[10]
Q10.
(a)
Mark in pairs 1 and 2 or 3 and 4.
1.
Tip produces IAA;
Accept auxin for IAA.
Accept affects amount of IAA.
Ignore contains/stores IAA.
2.
Affects concentration of IAA
OR
Affects (shoot) length/growth/elongation;
Accept affects independent variable.
Accept auxin for IAA.
Ignore affects results.
3.
Mitosis/division occurs in shoot tips;
4.
Affects (shoot) length/growth/elongation;
Ignore affects results.
2 max
(b)
1.
For respiration;
Ignore photosynthesis.
Ignore aerobic/anaerobic (respiration).
Reject glucose used in photosynthesis.
2.
Provide ATP/energy (for growth);
Reject produce energy.
Do not credit photosynthesis provides ATP.
2
(c)
1.
To prevent/reduce evaporation;
Accept evaporation of (IAA/glucose) ‘solution’.
Ignore contamination.
2.
(Which) alters concentration of (IAA) solution
OR
(Which) alters water potential;
Accept auxin for IAA.
2
(d)
1.
Increase in IAA concentration the higher/greater the mean (change in)
length;
Accept auxin for IAA.
2.
(High) IAA stimulates cell elongation;
Page 43 of 49
Accept auxin for IAA.
3.
In roots, growth/elongation less/inhibited;
Accept auxin for IAA.
Accept decrease in (mean) change in length but
reject ‘decreases length’ on its own.
Accept ‘opposite results or ‘negative correlation’.
3
(e)
0.4 and 39.6;
Both numbers required and must be in order shown.
1
[10]
Q11.
(a)
1.
Initial and final mass (of beaker and all contents);
Accept change in mass/weight
Ignore volume
Reject change in mass of celery/beaker/water alone
2.
Number of (groups of) xylem vessels;
Accept amount for ‘number’
2
(b)
Prevent evaporation/water loss
OR
(So) evaporation/water loss/transpiration only from celery;
1
(c)
1.
Water evaporates/is transpired (from leaves/ stalk/celery/plant);
2.
Water potential gradient/lower water potential creates
tension/pulls up water
OR
Osmosis creates tension/pulls up water;
Accept negative pressure for tension
3.
Hydrogen bonds/cohesion/adhesion maintains column;
3
(d)
1.
Cut away from body;
Accept description of cutting technique to avoid cutting fingers
2.
Against hard/non-slip/flat surface;
Accept named hard surface eg tile/board
2
(e)
Median (no mark)
1.
(Presence of) outliers/80/70
OR
Small sample size/8 (measurements);
Accept anomalies / extremes for ‘outliers’
2.
41;
Page 44 of 49
Accept for 1 mark,
Mean of 47
OR
Mode of 35
2
[10]
Q12.
(a)
Water
potential /
MPa
−1.95
Concentration of
sodium chloride
solution /
mol dm−3
0.04
Volume of
1 mol dm−3 sodium
chloride solution /
Volume of water
__________________
cm3
____________/ ____
cm3
__________________
0.8
19.2
___________________
__________________
_
1 mark for each row.
If values do not match the given unit, max 1.
Accept dm3 / mm3 for volume unit.
Accept 0.0008/8 x 10−4 and 0.0192/1.92 x 10−2
Accept 800 and 19200
Ignore units in 2nd row.
Do not accept mm−3/cm−3/dm−3/ ml
2
(b)
Correct answer of 0.07 (mol dm−3) = 2 marks;;
Incorrect answer 1 mark for any evidence of
48.6 to 48.8
OR
0.02
OR
0.7
OR
A final answer between 0.04 and 0.10
OR
A final answer of minus 0.07/−0.07;
Ignore minus signs on other 1 mark options.
2
(c)
Correct answer of 9 (cm2) = 2 marks;;
Incorrect answer 1 mark for evidence of water potential of
between -1.85 and -1.95 (MPa)
OR
growth of 15%
OR
69 (cm2)
OR
Page 45 of 49
A final answer between 8.7 and <9;
Allow 9.0
Accept correct reading labelled on the graph
shown on Figure 1 or Figure 2.
2
(d)
EITHER
1.
Low/slow growth;
2.
Due to smaller number/area of stomata (for gas exchange);
OR
3.
Growth may continue at lower water potentials;
4.
(Due to) adaptations in enzymes involved in photosynthesis/metabolic
reactions;
Mark as pair – 1 and 2 OR 3 and 4.
Reference to stomata must not relate only to water loss.
2 max
(e)
1.
Stomata close;
2.
Less carbon dioxide (uptake) for less photosynthesis/glucose
production;
‘Less’ only required once.
Reject ‘no photosynthesis’ but accept ‘carbon dioxide can’t enter
so less photosynthesis’.
Ignore oxygen for respiration but reject oxygen for photosynthesis.
Ignore less water for photosynthesis.
Accept only correct chemical formulae.
For ‘glucose’ accept named product of photosynthesis eg triose
phosphate, TP, amino acid, lipid.
2
[10]
Q13.
(a)
3.8;
Accept figures that round down to 3.8 ie (3.81 to 3.84)
Ignore: number of decimal places.
1
(b)
1.
(Index of diversity also) measures abundance / number / population
(size) of each species;
Ignore "total number of species" unqualified
Accept: every species for each species.
2.
(So useful because) may be many of some species
OR
(So useful because) may be few of other species;
2
(c)
1.
Movement of (floating) object over known distance and over given time
Page 46 of 49
OR
Time to fill container of known volume
OR
Use of data logging device;
Accept: digital device eg (digital) flow meter
1
(d)
Mark in paired statements.
Accept converse statements in context of site 2.
1.
Less food/prey at site 1;
More food/prey in site 2.
2.
(So more) mayfly starve;
(So) mayfly grow/ survive/reproduce.
OR
Less oxygen at site 1;
3.
4.
5.
6.
(So) less respiration/ATP/energy (for mayflies);
OR
More predators/Anglers’ Curse at site 1;
7.
(So more) mayfly killed/eaten/removed;
OR
More competition at site 1;
8.
(So more) mayfly starve;
2
(e)
Same size of area (sampled)
OR
Same size net/mesh
OR
Same sampling time
OR
Samples taken at same time of day/on same day;
Accept use of quadrat
Accept any other valid reason
1
[7]
Q14.
(a)
1.
Lowers activation energy;
2.
Induced fit causes active site (of enzyme) to change shape;
3.
(So) enzyme-substrate complex causes bonds to form/break;
Accept: description, of induced fit
Accept: enzyme-substrate complex causes stress/strain on bonds.
3
(b)
Size/dimensions /mass/variety of potato
OR
Temperature (of solution/flask)
Page 47 of 49
OR
pH (of solution);
Accept : weight of potato
Ignore : amount of potato
Ignore concentration/ volume of catalase
1
(c)
0.33, 0.60, 0.86, 1.0, 1.0 = 2 marks;;
2 significant figures
If answer incorrect accept for 1 mark,
Correct values but incorrect number of significant figures
OR
1.0 written on row for hydrogen peroxide 2.0/2.5 in the table
OR
Answers showing correct division, eg 0.3, 0.6, 0.9
OR
Answers showing correct significant figures using incorrect
calculation (÷18) 1.0, 0.56, 0.39, 0.33, 0.33
2
(d)
1.
Hydrogen peroxide concentration on x axis and rate of reaction on Y
axis, linear number sequence and appropriate scale;
Graph should cover half or more of the grid; eg reject if Y axis
covers only three big squares
2.
Correct units /mol dm−3 and /arbitrary units/au;
Accept brackets instead of solidus
3.
All co-ordinates plotted accurately with point-to-point or smooth curve;
Accept accurate plotting of co-ordinates given in part (c)
Reject : bar chart
Reject : if ruled straight line of best fit
Accept: if x axis starts at 0.5
Accept: if line is extended to (0,0)
Plot coordinates must be processed data, hydrogen peroxide vs
time = 0
3
(e)
Cut up/use discs/homogenise/increase surface area (of potato chips)
OR
Use bigger chips
OR
Increase temperature
OR
Change pH;
Reject answer if the temperature is above 40°C
Ignore: more/increase heat
1
Page 48 of 49
[10]
Page 49 of 49