Q1.
This question should be written in continuous prose, where appropriate.
(a)
Explain how a resting potential is maintained in a neurone.
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(4)
(b)
In an investigation, an impulse was generated in a neurone using electrodes. During
transmission along the neurone, an action potential was recorded at one point on the
neurone. When the impulse reached the neuromuscular junction, it stimulated a muscle
cell to contract. The force generated by the contraction was measured. The results are
shown in the graph.
The distance between the point on the neurone where the action potential was measured
and the neuromuscular junction was exactly 18 mm.
(i)
Use the graph to estimate the time between the maximum depolarisation and the
start of contraction by the muscle cell.
Time ................................ ms
(1)
Page 1 of 42
(ii)
Use your answer to part (i) to calculate the speed of transmission along this neurone
to the muscle cell. Give your answer in mm per second.
Show your working.
Speed .................................. mm s–1
(2)
(iii)
Give one reason why the value calculated in part (ii) would be an underestimate of
the speed of transmission of an impulse along a neurone.
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(1)
Acetylcholine is the neurotransmitter at neuromuscular junctions.
(c)
Describe how the release of acetylcholine into a neuromuscular junction causes the cell
membrane of a muscle fibre to depolarise.
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(3)
(d)
Use your knowledge of the processes occurring at a neuromuscular junction to explain
each of the following.
(i)
The cobra is a very poisonous snake. The molecular structure of cobra toxin is
similar to the molecular structure of acetylcholine. The toxin permanently prevents
muscle contraction.
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(2)
Page 2 of 42
(ii)
The insecticide DFP combines with the active site of the enzyme
acetylcholinesterase. The muscles stay contracted until the insecticide is lost from
the neuromuscular junction.
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(2)
(Total 15 marks)
Q2.
S
(a)
In an investigation, the effects of caffeine on performance during exercise were
measured. One group of athletes (A) was given a drink of decaffeinated coffee. Another
group (B) was given a drink of decaffeinated coffee with caffeine added. One hour later the
athletes started riding an exercise bike and continued until too exhausted to carry on.
Three days later the same athletes repeated the experiment, with the drinks exchanged.
(i)
The researchers added caffeine to decaffeinated coffee. Explain why they did not just
use normal coffee.
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(1)
(ii)
The performance of the athletes might have been influenced by how they expected
the caffeine to affect them. How could the researchers avoid this possibility?
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(1)
During the exercise the concentrations of glycerol and fatty acids in the blood plasma were
measured. The results are shown in the table.
Drink
Mean time to
exhaustion
/minutes
Mean
concentration of
blood glycerol/
Mean
concentration of
blood fatty acids/
mmol dm–3
mmol dm–3
With caffeine
90.2
0.20
0.53
Without caffeine
75.5
0.09
0.31
(b)
(i)
Describe the effect of caffeine on exercise performance.
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(1)
Page 3 of 42
(ii)
Suggest one explanation for the higher glycerol and fatty acid concentrations in the
blood plasma of the athletes after they were given caffeine.
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(2)
(c)
The researchers measured the volumes of carbon dioxide exhaled and oxygen inhaled
during the exercise. From the results they calculated the respiratory quotient (RQ), using
the formula
When a person is respiring carbohydrate only, RQ = 1.0
When a person is respiring fatty acids only, RQ = 0.7
(i)
The basic equation for the respiration of glucose is
C6H12O6 + 6O2 → 6CO2 + 6H2O
Explain why the RQ for glucose is 1.0.
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(2)
Page 4 of 42
(ii)
The researchers found that, when the athletes were given the drink containing
caffeine, their mean RQ was 0.85. When given the drink without caffeine their mean
RQ was 0.92.
The researchers concluded that when the athletes had caffeine they used glycogen
more slowly than when they did not have caffeine, and that the store of glycogen in
their muscles was used up less quickly during the exercise.
Explain the evidence from the information above and from the table which supports
these conclusions.
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(3)
(Total 10 marks)
Q3.
After moving from bright light into darkness, it takes several minutes for the rod cells to
recover their sensitivity. Researchers measured the ability of the rod cells to detect small spots
of light of different colours and intensity after a person moved into darkness. The results are
shown in Figure 1.
Figure 2 shows the amount of light of different wavelengths that rhodopsin absorbs.
Figure 1
Figure 2
Page 5 of 42
(i)
Explain why it takes time for the rod cells to recover their sensitivity to light after moving
into darkness.
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(2)
(ii)
Use information in Figures 1 and 2 to explain the differences in sensitivity of rod cells to
red and green light.
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(2)
(iii)
Suggest an explanation for the difference in sensitivity of rod cells to the white and green
spots after 30 minutes.
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(1)
(Total 5 marks)
Page 6 of 42
Q4.
The diagram shows the change in the charge across the surface membrane of a nonmyelinated axon when an action potential is produced.
(a)
Describe how the change shown in the diagram occurs when an action potential is
produced.
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(2)
(b)
Explain what causes the conduction of impulses along a non-myelinated axon to be slower
than along a myelinated axon.
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(3)
(Total 5 marks)
Page 7 of 42
Q5.
S
In an investigation by a student into the responses of maggots, the bottom of a large
box was marked with six coloured segments, as shown in the diagram.
30 maggots were placed on each segment in the box. A transparent cover was put on the
box and light bulbs were positioned so that the segments were evenly illuminated. The
positions of the maggots were recorded after one hour. The intensity of the light reflected
by each segment was measured.
The experiment was repeated three more times. The total number of maggots in each
segment from the four experiments is shown in the table.
(a)
Colour of
segment
Intensity of reflected light /
arbitrary units
Total number of maggots
Black
4
154
Red
25
229
Blue
10
178
White
44
47
Green
25
48
Yellow
40
64
Give one conclusion about the responses of maggots which is supported by these results.
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Give the evidence from the table for your conclusion.
......................................................................................................................
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(2)
(b)
The chi-squared test was used to analyse the data. For the results obtained, suggest one
null hypothesis which might be analysed by a chi-squared test.
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(1)
Page 8 of 42
(c)
It was suggested that the movement of the maggots might have been influenced by the
Earth’s magnetic field. Suggest one simple way of repeating the investigation which would
avoid this possibility.
......................................................................................................................
......................................................................................................................
(1)
(Total 4 marks)
Q6.
(a)
(i)
The diagram shows the banding pattern observed in part of a relaxed muscle fibril.
Describe what causes the different bands seen in the muscle fibril.
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(2)
(ii)
Describe how the banding pattern will be different when the muscle fibril is
contracted.
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(2)
Page 9 of 42
(b)
There is an increase in the activity of the enzyme ATPase during muscle contraction. An
investigation into muscle contraction involved measuring the activity of ATPase in solutions
containing ATP, myosin and different muscle components. The table shows the results.
Solution
(i)
Contents
ATPase activity /
arbitrary units
A
ATP, myosin and actin
1.97
B
ATP, myosin, actin and tropomyosin
0.54
C
ATP, myosin, actin, tropomyosin and calcium ions
3.85
Explain the importance of ATPase during muscle contraction.
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(2)
(ii)
Using your knowledge of muscle contraction, explain the difference in the results
between
A and B;
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(2)
B and C.
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(2)
(Total 10 marks)
Page 10 of 42
Q7.
The diagram shows the distribution of cone cells across the retina of a human eye.
(a)
On the diagram draw a line to show the distribution of rod cells across the retina.
(2)
(b)
Nocturnal mammals are active at night. Describe how the number and distribution of rods
and cones across the retina would differ in a nocturnal mammal from the number and
distribution in a human. Explain your answer.
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(3)
(Total 5 marks)
Page 11 of 42
Q8.
Acetylcholine is a neurotransmitter which binds to postsynaptic membranes and stimulates
the production of nerve impulses. GABA is another neurotransmitter. It is produced by certain
neurones in the brain and spinal cord. GABA binds to postsynaptic membranes and inhibits the
production of nerve impulses. The diagram shows a synapse involving three neurones.
(a)
Describe the sequence of events leading to the release of acetylcholine and its binding to
the postsynaptic membrane.
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(4)
(b)
The binding of GABA to receptors on postsynaptic membranes causes negatively charged
chloride ions to enter postsynaptic neurones. Explain how this will inhibit transmission of
nerve impulses by postsynaptic neurones.
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(3)
Page 12 of 42
(c)
Epilepsy may result when there is increased neuronal activity in the brain.
(i)
One form of epilepsy is due to insufficient GABA. GABA is broken down on the
postsynaptic membrane by the enzyme GABA transaminase. Vigabatrin is a new
drug being used to treat this form of epilepsy. The drug has a similar molecular
structure to GABA. Suggest how Vigabatrin may be effective in treating this form of
epilepsy.
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.............................................................................................................
(2)
(ii)
A different form of epilepsy has been linked to an abnormality in GABA receptors.
Suggest and explain how an abnormality in GABA receptors may result in epilepsy.
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(3)
(Total 12 marks)
Page 13 of 42
Q9.
The resting potential of a neurone is maintained by the unequal distribution of ions inside and
outside the plasma membrane. The diagram shows the plasma membrane of a neurone and the
three different proteins that are involved in maintaining the resting potential.
(a)
Protein C requires ATP to function. Describe the role of protein C.
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(2)
S
(b)
(i)
Proteins A and B differ from each other. Explain why different proteins are required
for the diffusion of different ions through the membrane.
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(2)
(ii)
The plasma membrane of the neurone is more permeable to potassium ions than to
sodium ions. Give the evidence from the diagram that supports this observation.
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(1)
(Total 5 marks)
Page 14 of 42
Q10.
Secretion of neurotransmitters into a synaptic cleft may produce an action potential in a
postsynaptic neurone.
(i)
Explain how the release of acetylcholine at an excitatory synapse reduces the membrane
potential of the postsynaptic membrane.
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(2)
(ii)
Explain what causes transmission at a synapse to occur in only one direction.
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(2)
(iii)
GABA is a neurotransmitter which inhibits the production of action potentials.
The diagram and the graph show how the release of GABA from a presynaptic membrane
affects the membrane potential of a postsynaptic membrane.
Page 15 of 42
When the postsynaptic membrane is stimulated by acetylcholine, an action potential is
less likely if GABA is released at the same time. Explain why.
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(4)
(Total 8 marks)
Q11.
Essay
You should write your essay in continuous prose.
Your essay will be marked for its scientific accuracy.
It will also be marked for your selection of relevant material from different parts of the
specification and for the quality of your written communication.
The maximum number of marks that can be awarded is
Scientific
Breadth of knowledge
Relevance
Quality of written communication
16
3
3
3
Write an essay on the following topic:
Negative feedback and its importance in biology.
(Total 25 marks)
Page 16 of 42
Q12.
A frog’s heart was attached to an instrument which measured the force produced as the
heart contracted. Graph 1 shows the changes in force when the heart was bathed in a solution
of salts at 20 °C. Graph 2 shows the results when the heart was bathed in the same solution at
the same temperature, but including acetylcholine.
(a)
Points A and B show when the atria and ventricle were contracting. Which point, A or B,
shows contraction of the ventricle? Give two reasons for your answer.
Point .....................................
Reason 1 ......................................................................................................
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Reason 2 ......................................................................................................
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(2)
(b)
Calculate the frog’s heart rate when acetylcholine was not present. Show your working.
Heart rate = .................................... beats per minute.
(2)
Page 17 of 42
(c)
(i)
From the graphs, what can you conclude about the effect of acetylcholine on
heart rate;
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stroke volume?
.............................................................................................................
(2)
(ii)
Use your answer to part (i) to explain the effect of acetylcholine on cardiac output.
.............................................................................................................
.............................................................................................................
(1)
(iii)
Addition of acetylcholine in the experiment mimics the effect of one branch of the
autonomic nervous system. Which branch is this?
.............................................................................................................
(1)
(d)
(i)
Explain how nervous control in a human can cause increased cardiac output during
exercise.
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(4)
Page 18 of 42
(ii)
Explain why increased cardiac output is an advantage during exercise.
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(3)
(Total 15 marks)
Q13.
The diagram shows part of the retina in a human eye.
(a)
Explain each of the following observations.
(i)
When light falls on cells 1 and 2, only one spot of light is seen. But, when light falls on
cells 2 and 3, two spots of light are seen.
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(1)
Page 19 of 42
(ii)
When one unit of light energy falls on cell 3, no light is seen. But, when one unit of
light energy falls on cell 3, one unit falls on cell 4 and one unit falls on cell 5, light is
seen.
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(3)
(b)
Cells of the same type as cells 6 and 7 are found in large numbers at the fovea. This
results in colour vision with high visual acuity.
Explain what causes vision using the fovea.
(i)
to be in colour;
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.............................................................................................................
(1)
(ii)
to have high visual acuity.
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(1)
(Total 6 marks)
Page 20 of 42
Q14.
Essay
You should write your essay in continuous prose.
Your essay will be marked for its scientific accuracy.
It will also be marked for your selection of relevant material from different parts of the
specification and for the quality of your written communication.
The maximum number of marks that can be awarded is
Scientific
Breadth of knowledge
Relevance
Quality of written communication
16
3
3
3
Write an essay on the following topic:
Inorganic ions include those of sodium, phosphorus and hydrogen. Describe how these and
other inorganic ions are used in living organisms.
(Total 25 marks)
Q15.
The graph shows the electrical changes measured across the plasma membrane of an
axon during the passage of a single action potential.
(a)
Explain the shape of the curve
(i)
over the range labelled A;
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(2)
Page 21 of 42
(ii)
over the range labelled B;
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.............................................................................................................
(1)
(b)
Fewer action potentials occur along a myelinated axon than along an unmyelinated axon of
the same length. Explain why.
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(2)
(Total 5 marks)
Q16.
(a) Effectors bring about responses in the body. They are stimulated when neurones
secrete substances, called neurotransmitters, on to them.
(i)
Name the type of neurone that stimulates muscles.
.............................................................................................................
(1)
(ii)
Other than muscle tissue, name one type of tissue that acts as an effector.
.............................................................................................................
(1)
(b)
Substances, called hormones, can also stimulate effectors.
Humans produce a large number of different hormones but only a small number of
different neurotransmitters. Explain the significance of this difference.
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(3)
(Total 5 marks)
Page 22 of 42
Q17.
During an action potential, the permeability of the cell-surface membrane of an axon
changes. The graph shows changes in permeability of the membrane to sodium ions (Na+) and
to potassium ions (K+) during a single action potential.
(a)
Explain the shape of the curve for sodium ions between 0.5 ms and 0.7ms.
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(3)
(b)
During an action potential, the membrane potential rises to +40 mV and then falls. Use
information from the graph to explain the fall in membrane potential.
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(3)
Page 23 of 42
(c)
After exercise, some ATP is used to re-establish the resting potential in axons. Explain
how the resting potential is re-established.
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(2)
(Total 8 marks)
Q18.
Different substances are involved in coordinating responses in animals.
(a)
Hormones are different from local chemical mediators such as histamine in the cells they
affect.
(i)
Describe how hormones are different in the cells they affect.
.............................................................................................................
.............................................................................................................
(1)
(ii)
Describe how hormones and local chemical mediators reach the cells they affect.
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(2)
(b)
Synapses are unidirectional. Explain how acetylcholine contributes to a synapse being
unidirectional.
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(2)
Page 24 of 42
(c)
Cells in the stomach wall release gastric juice after a meal. The graph shows how the
volumes of gastric juice produced by nervous stimulation and by hormonal stimulation
change after a meal.
(i)
Describe the evidence from the graph that curve A represents the volume of gastric
juice produced by nervous stimulation.
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.............................................................................................................
.............................................................................................................
.............................................................................................................
(2)
(ii)
Complete the table to show the percentage of gastric juice produced by nervous
stimulation at the times shown.
Time after meal / hours
1
2
3
Percentage of gastric
juice produced by
nervous stimulation
(1)
(Total 8 marks)
Page 25 of 42
Q19.
The black mamba is a poisonous snake. Its poison contains a toxin.
The table shows the base sequence of mRNA that codes for the first two amino acids of this
toxin.
Base sequence of anticodon on tRNA
Base sequence of mRNA
A
C
G
A
U
G
Base sequence of DNA
Complete the table to show
(a)
(i)
the base sequence of the anticodon on the first tRNA molecule that would bind to
this mRNA sequence
(1)
(ii)
the base sequence of the DNA from which this mRNA was transcribed.
(1)
(b)
The length of the section of DNA that codes for the complete toxin is longer than the
mRNA used for translation. Explain why.
........................................................................................................................
........................................................................................................................
........................................................................................................................
(1)
(c)
A mutation in the base sequence of the DNA that codes for the toxin would change the
base sequence of the mRNA.
Explain how a change in the base sequence of the mRNA could lead to a change in the
tertiary structure of the toxin.
........................................................................................................................
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........................................................................................................................
(1)
Page 26 of 42
(d)
The black mamba’s toxin kills prey by preventing their breathing. It does this by inhibiting
the enzyme acetylcholinesterase at neuromuscular junctions. Explain how this prevents
breathing.
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(Extra space) .................................................................................................
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(3)
(Total 7 marks)
Page 27 of 42
M1.
(a) membrane relatively impermeable / less permeable to sodium ions /
gated channels are closed / fewer channels;
sodium ions pumped / actively transported out;
by sodium ion carrier / intrinsic proteins;
higher concentration of sodium ions outside the neurone;
inside negative compared to outside / 3 sodium ions out for two
potassium ions in;
(if sodium mentioned but not in context of ions,
negate 1 mark)
4 max
(b)
(i)
1.6;
1
(ii)
18 ÷ 1.6 = 11.25;
multiply by 1000 to convert from ms to s / 11 250;
(correct method = 1 mark, i.e.
or × 1000)
(correct answer based on (b)(i) = 2 marks)
2
(iii)
time for transmission / diffusion across the neuromuscular
junction / synapse;
time for muscle (fibrils) to contract;
1 max
(c)
movement by diffusion;
binding to receptors on (post-synaptic) membrane;
causing sodium channels to open / sodium ions to move in
to muscle (cell);
3
(d)
(i)
toxin binds to/competes for / blocks the acetylcholine receptors;
acetylcholine can not depolarise the membrane /
the toxin does not cause depolarisation;
(allow references to generating action potentials instead of
depolarisation, do not allow references to impulses in muscles)
2
(ii)
acetylcholinesterase is unable to breakdown acetylcholine;
acetylcholine still available to depolarise the membrane /
generate action potentials in the membrane;
2
[15]
M2.
(a)
(i)
in case normal coffee differs in some other way;
to control concentration of caffeine;
1 max
(ii)
not telling them what the drink contained / purpose of experiment;
1
Page 28 of 42
(b)
(i)
able to continue for longer; (not just increases performance)
(disqualify if also refers to fatty acids and glycerol)
1
(ii)
breakdown of fats;
at increased rate / by mobilisation of fat stores;
2
(c)
(i)
idea that volumes of oxygen and carbon dioxide the same;
reference to equal moles, or quotient as 1 divided by 1/ or 6 by 6;
2
(ii)
glycogen is a carbohydrate / broken down to glucose, linked to RQ;
with no caffeine, RQ nearer 1.0 / less carbon dioxide exhaled and
more oxygen inhaled (or vice versa);
with caffeine higher proportion of fats/fatty acids respired;
increased time to exhaustion suggests slower use of glycogen:
3 max
[10]
M3.
(i)
rhodopsin bleached/broken down by light;
time for resynthesis;
2
(ii)
rhodopsin/pigment absorbs green light more readily than red / is
more sensitive to green light;
(after resynthesis) less (intense) green light needed to break down
rhodopsin (than red);
2
(iii)
white has (high proportion of) wavelengths to which rhodopsin not
sensitive;
1
[5]
M4.
(a) sodium gates or channels open / increase in permeability of axon
membrane to sodium ion;
sodium ions enter axon;
2
(c)
non-myelinated – next section of membrane depolarised / whole
membrane;
myelinated – depolarisation / ion movement only at nodes;
impulse jumps from node to node /saltatory conduction;
3
[5]
Page 29 of 42
M5.
(a) one mark for conclusion:
maggots move to/respond to/prefer/like /red rather than green;
(reject ‘most prefer red’)
maggots move to/prefer/like areas of lower light intensity (except green);
maggots respond more to colour than light intensity / do not respond to
differences in light intensity;
(reject conclusion relating to single result)
one mark for:
evidence matching conclusion:
more in red than green, but light intensity the same;
more in segments with lower light intensity;
more differences in different colours, little difference in light intensity;
large difference in number of maggots on segments with 25 a.u.
light intensity;
2 max
(b)
valid statement expressed as null hypothesis, i.e. in negative
form, e.g. no difference in response to different colours / light intensities;
(must relate to a possible hypothesis)
1
(c)
rotate box (so segments in different direction) / change order of coloured
segments;
place magnets around box / create alternative magnetic field;
1 max
[4]
M6.
(a)
(i)
A / dark band is mainly due to myosin filaments;
H zone only myosin filaments;
darker band has both types of filament;
light band has only actin filaments;
2 max
(ii)
H zone narrows;
light band narrows;
outer darker regions of A / dark band widen;
2 max
Page 30 of 42
(b)
(i)
breaks down ATP yielding energy;
used to form / break actomyosin bridges;
2
(ii)
A and B
tropomyosin covers binding site on actin;
no cross bridges formed /
ATPase activity on myosin head reduced;
2
B and C
calcium ions remove tropomyosin;
binding / calcium ions increase ATPase activity;
2
[10]
M7.
(a) no rods at blind spot or fovea;
greater distribution of rods at edge;
2
(b)
more rods and no / fewer cones present;
rods at the fovea / rods not mainly at periphery;
rods have high sensitivity / show retinal convergence /
converse for cones;
rhodopsin ‘bleached’ at low light intensities / iodopsin ‘bleached’;
at high light intensities;
3 max
[5]
M8.
(a) action potential arrives / depolarisation occurs;
calcium ions enter synaptic knob;
vesicles fuse with membrane;
acetylcholine diffuses (across synaptic cleft);
binds to receptors;
4 max
(b)
inside becomes more negatively charged / hyperpolarised; stimulation
does not reach threshold level / action potential not produced;
depolarisation does not occur / reduces effect of sodium ions entering;
3
Page 31 of 42
(c)
(i)
inhibits enzyme (which breaks down GABA);
more GABA available (to inhibit neurone);
OR
binds to (GABA) receptors;
inhibits neuronal activity / chloride ions enter (neurone);
2 max
(ii)
receptors have different tertiary/3D structure/shape not
complementary;
GABA cannot bind; inhibition of neuronal activity does not occur /
chloride ions do not enter;
3
[12]
(a) Transports Na+ and K+ ;
By active transport / pump / against concentration gradient;
Restores ion balance after an action potential;
[reject K+ out and Na+ in]
M9.
2
(b)
(i)
each protein has a specific tertiary structure/shape;
because the ions have different sizes/shape/charge;
[reject receptors binding]
max 2
(ii)
fewer protein B molecules, which transport sodium ions;
more protein A molecules, which transport potassium ions;
max 1
[5]
(i)
Binds to receptor/proteins; and opens Na+ channels;
Na+ enter and make membrane potential less negative/depolarised
M10.
2
(ii)
(Vesicles containing) neurotransmitter only in presynaptic membrane/
neurone;
receptor/proteins only in postsynaptic membrane/neurone;
so neurotransmitter diffuses down concentration gradient;
max 2
Page 32 of 42
(iii)
GABA opens K+ and Cl– channels;
K+ passes out and Cl– passes in;
Membrane potential more negative/hyperpolarised;
Requires increased stimulation/must open more Na+ channels/allow
more Na+ to enter;
To reach threshold;
max 4
[8]
M11.
General Principles for marking the Essay:
Four skill areas will be marked: scientific content, breadth of knowledge, relevance and quality of
language. The following descriptors will form a basis for marking.
Scientific Content (maximum 16 marks)
Category
Mark
16
14
Good
Descriptor
Most of the material of a high standard
reflecting a comprehensive understanding of
the principles involved and a knowledge of
factual detail fully in keeping with a
programme of A-level study. Some material,
however, may be a little superficial. Material is
accurate and free from fundamental errors
but there may be minor errors which detract
from the overall accuracy.
12
10
8
Average
A significant amount of the content is of an
appropriate depth, reflecting the depth of
treatment expected from a programme of Alevel study. Generally accurate with few, if
any fundamental errors. Shows a sound
understanding of most of the principles
involved.
6
4
2
Poor
Material presented is largely superficial and
fails to reflect the depth of treatment expected
from a programme of A-level study.
If greater depth of knowledge is
demonstrated, then there are many
fundamental errors.
0
Page 33 of 42
Breadth of Knowledge (maximum 3 marks)
Mark
3
2
1
0
Descriptor
A balanced account making reference to most if not all areas that might
realistically be covered on an A-level course of study.
A number of aspects covered but a lack of balance. Some topics
essential to an understanding at this level not covered.
Unbalanced account with all or almost all material based on a single
aspect
Material entirely irrelevant.
Relevance (maximum 3 marks)
Mark
3
2
1
0
Descriptor
All material presented is clearly relevant to the title. Allowance should be
made for judicious use of introductory material
Material generally selected in support of title but some of the main
content of the essay is of only marginal relevance.
Some attempt made to relate material to the title but considerable
amounts largely irrelevant.
Material entirely irrelevant or too limited in quantity to judge.
Quality of language (maximum 3 marks)
Mark
3
2
1
0
Descriptor
Material is logically presented in clear, scientific English. Technical
terminology has been used effectively and accurately throughout.
Account is logical and generally presented in clear, scientific English.
Technical terminology has been used effectively and is usually accurate.
The essay is generally poorly constructed and often fails to use an
appropriate scientific style and terminology to express ideas.
Material entirely irrelevant or too limited in quantity to judge.
[25]
Additional notes
Care must be taken in using these notes. It is important to appreciate that the only criteria to be
used in awarding marks to a particular essay are those corresponding to the appropriate
descriptors. Candidates may gain credit for any information providing that it is biologically
accurate, relevant and of a depth in keeping with an A-level course of study. Material used in the
essay does not have to be taken from the specification, although it is likely that it will.
These notes must therefore be seen merely as guidelines providing an indication of areas of the
specification from which suitable factual material might be drawn.
In determining the mark awarded for breadth, content should ideally be drawn from each of the
areas specified if maximum credit is to be awarded. Where the content is drawn from two areas,
two marks should be awarded and where it is taken only from a single area, one mark should be
awarded. However, this should only serve as a guide. This list is not exhaustive and examiners
should be prepared to offer credit for the incorporation of relevant material from other areas of
study.
Page 34 of 42
(a) B – It is the 2nd contraction / occurs (immediately) after A / occurs
after atrium;
Larger / more force / more pressure;
M12.
2
(b)
= 37 to 38
allow 1 mark if correct working shown
max 2
(c)
(i)
(Heart rate)
(Stroke volume)
reduced;
no effect;
2
(ii)
Reduced because C.O. = H.R. x S.V. / connection argument based on
reduced H.R;
1
(iii)
Parasympathetic;
1
(d)
(i)
1. Coordination via medulla (of brain) / cardiac centre;
2. (Increased) impulses along sympathetic (/ cardiac accelerator)
nerve;
3. To S.A. node / pacemaker;
4. Release of noradrenalin;
5. More impulses sent from / increased rate of discharge of
S.A. node / pacemaker;
Not “beats”; not “speeds up”
6. Increased heart rate / increased stroke volume;
max 4
(ii)
In exercise – More energy release / more respiration / actively
respiring muscles / for aerobic respiration;
Higher cardiac output – Increases O2 supply (to muscles);
Increases glucose supply (to muscles);
Increases CO2 removal (from muscles) /
lactate removal;
Increases heat removal (from muscles) /
for cooling;
If no “increase” – max 2 marks
3
[15]
Page 35 of 42
M13.
(a)
(i)
1 and 2 share neurone but 2 and 3 have separate neurones (to brain);
Ignore wrong names of neurones
1
(ii)
1 unit is sub-threshold / 3 units are above threshold / give sufficient
depolarisation;
(1 unit) No impulses / no action potential / in (sensory) neurone /
does not stimulate (sensory) neurone / 3 units → impulses;
(Spatial) summation / sufficient neurotransmitter released / from
3 receptors / insufficient N-T from one;
Reject ‘temporal’
3
(b)
(i)
(Three) different types of (cone) cells / types 6 and 7 sensitive
to different wavelengths / different frequencies / different colours;
(ii)
Impulses along separate neurone from each receptor cell / each
receptor cell connects to separate neurone;
2
[6]
Page 36 of 42
M14.
General principles for marking the Essay:
Four skill areas will be marked: scientific content, breadth of knowledge,
relevance and quality of language. The following descriptors will form a
basis for marking.
Scientific content (maximum 16 marks)
Category
Good
Mark
16
14
Descriptor
Most of the material of a high standard reflecting a
comprehensive understanding of the principles
involved and a knowledge of factual detail fully in
keeping with a programme of A-level study. Some
material, however, may be a little superficial. Material
is accurate and free from fundamental errors but
there may be minor errors which detract from the
overall accuracy.
12
10
Average
8
A significant amount of the content is of an
appropriate depth, reflecting the depth of treatment
expected from a programme of A-level study.
Generally accurate with few, if any fundamental
errors. Shows a sound understanding of most of the
principles involved.
6
4
Poor
2
Material presented is largely superficial and fails to
reflect the depth of treatment expected from a
programme of A-level study. If greater depth of
knowledge is demonstrated, then there are many
fundamental errors.
0
Breadth of Knowledge (maximum 3 marks)
Mark
3
2
1
0
Descriptor
A balanced account making reference to most if not all areas
that might realistically be covered on an A-level course of study.
A number of aspects covered but a lack of balance. Some
topics essential to an understanding at this level not covered.
Unbalanced account with all or almost all material based on a
single aspect
Material entirely irrelevant.
Relevance (maximum 3 marks)
Mark
3
2
1
0
Descriptor
All material presented is clearly relevant to the title. Allowance
should be made for judicious use of introductory material
Material generally selected in support of title but some of the
main content of the essay is of only marginal relevance.
Some attempt made to relate material to the title but
considerable amounts largely irrelevant.
Material entirely irrelevant or too limited in quantity to judge.
Page 37 of 42
Quality of language (maximum 3 marks)
Mark
3
2
1
0
Descriptor
Material is logically presented in clear, scientific English.
Technical terminology has been used effectively and accurately
throughout.
Account is logical and generally presented in clear, scientific
English. Technical terminology has been used effectively and is
usually accurate.
The essay is generally poorly constructed and often fails to use
an appropriate scientific style and terminology to express ideas.
Material entirely irrelevant or too limited in quantity to judge.
[25]
Additional notes on marking
Care must be taken in using these notes. It is important to appreciate that the only criteria to be
used in awarding marks to a particular essay are those corresponding to the appropriate
descriptors. Candidates may gain credit for any information providing that it is biologically
accurate, relevant and of a depth in keeping with an A-level course of study. Material used in the
essay does not have to be taken from the specification, although it is likely that it will be. These
notes must therefore be seen merely as guidelines providing an indication of areas of the
specification from which suitable factual material might be drawn.
In determining the mark awarded for breadth, content should ideally be drawn from each of the
areas specified if maximum credit is to be awarded. Where the content is drawn from two
areas, two marks should be awarded and where it is taken only from a single area, one mark
should be awarded. However, this should only serve as a guide. This list is not exhaustive and
examiners should be prepared to offer credit for the incorporation of relevant material from other
areas of study.
M15.
(a)
(i)
Sodium ions move out of axon;
By diffusion/down concentration gradient;
Through sodium ion channels/sodium ion channels open;
2 max
(ii)
Potassium ions enter / potassium ion channels open;
1
(b)
Myelin insulates axon / ions can only pass through (plasma membrane
of axon) at gaps in myelin sheath;
(Gaps in sheath are called) nodes of Ranvier;
Q The second marking point should be awarded only where
answers include the correct scientific term.
2
[5]
Page 38 of 42
M16.
(a)
(i)
Motor;
1
(ii)
Gland / glandular;
Q Answers that name a specific gland may be awarded credit.
1
(b)
Hormones reach all cells (via blood);
Neurotransmitters secreted directly on to target cell;
Different hormones specific to different target cells;
3
[5]
M17.
(a) (Ion) channel proteins open;
Sodium in;
Changes membrane potential/makes inside of axon less
negative/positive/depolarisation/reaches threshold;
More channels open/positive feedback;
Accept other phrases for ion channel proteins providing that it is
clear that it is something through which ions pass.
Reject carrier.
First marking point relates to opening.
Third point must relate to more (channels) opening.
3 max
(b)
Potassium channels open;
Potassium out;
Sodium channels close;
Do not penalise candidate who refers to sodium or potassium. Ions
are mentioned in question.
Reject pump
3
(c)
Pump/active transport/transport against concentration gradient;
Of sodium from axon/sodium out/of potassium in;
Do not penalise candidate who refers to sodium or potassium. Ions
are mentioned in question
2
[8]
M18.
(a)
(i)
Hormones have widespread effect / affect different organs / affect
different parts of the body / affect distant organs / only affect cells with right receptor;
Assume “they” refers to hormones.
1
Page 39 of 42
(ii)
1. Hormones in blood;
2. Local chemical mediators spread by diffusion / spread directly;
1. May be awarded where candidates refer to both as “they”.
2
(b)
1. (Acetylcholine) released from/in presynaptic side;
2. Diffusion from higher concentration/to lower concentration;
3. Receptors in postsynaptic (side) / binds on postsynaptic (side);
2. Mark for diffusion only awarded in context of unidirectional
movement.
2 max
(c)
(i)
1. Rapid response;
2. Short duration;
Specific wording is not important. It is the principles that matter
here.
Points may be made by referring to figures.
2
(ii)
Percentage
1
2
3
80
0
0
Ignore % sign.
1
[8]
M19.
(a)
(i)
UGC;
1
(ii)
TGCTAC;
1
(b)
(DNA) contains introns / non-coding bases / mRNA only contains exons /
coding bases;
Assume that ‘it’ refers to DNA
Neutral: DNA contains introns and exons
Neutral: ‘splicing’
Neutral: pre-mRNA contains introns
Ignore refs. to start and stop codons
1
(c)
Different primary structure / amino acid sequence / amino acid coded for;
Reject: different amino acids produced / formed
Neutral: refs. to bonds
1
Page 40 of 42
(d)
1.
Acetylcholine not broken down / stays bound to receptor;
2.
Na+ ions (continue to) enter / (continued) depolarisation / Na+ channels
(kept) open / action potentials / impulses fired (continuously);
3.
(Intercostal) muscles stay contracted / cannot relax;
3. ‘Muscles contract’ is not enough
Accept: diaphragm stays contracted / cannot relax
3
[7]
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