The diagram shows a section through a leaf.
(i) Complete the sentence by putting a cross (
The cell that will make the most glucose is
) in the box next to your answer.
(1)
A
B
C
D
(ii) Describe how carbon dioxide enters the leaf.
(2)
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(iii) Describe the process that takes place in the leaf to produce oxygen.
(3)
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(b) An investigation was carried out to measure water loss from a plant, at four different temperatures.
The diagram shows the apparatus used.
(c) Explain how glucose production could be affected if this plant lost a lot of water.
(2)
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Examiner's Report
Q1.
(i)–(ii)
Candidates did not seem to be phased by Q1 being about photosynthesis and some very good responses
were seen. Very few blank responses were seen. The multiplechoice part (a)(i) was answered correctly
by many candidates with the commonest incorrect response being C, the spongy mesophyll cell.
In part (a)(ii), many candidates mentioned that carbon dioxide entered through the stomata but did not
extend their answers further.
Results Plus: Examiner Comments
This candidate did score two marks but got side-tracked into giving information irrelevant to the
question (which we can ignore). The last statement is a bit ambiguous as to what 'it' refers to,
but we gave benefit of the doubt as the rest of the account was clear.
Results Plus: Examiner Tip
Try to avoid the use of words like 'it' and 'they'. It is safer to use the noun that you are
referring to.
Results Plus: Examiner Comments
This was a common one-mark response that we saw, even from the better candidates.
This particular answer earned only one of the two marks available by omitting any
reference to the process of diffusion.
Results Plus: Examiner Tip
Always look to see how many marks have been allocated to a question. Then make
sure that you give the same number of scientific facts as there are marks. You will not
be awarded two marks for one piece of information.
(iii)
We saw some very good answers to this question on photosynthesis, although it is a topic that
candidates typically have difficulty with. It is worth noting that we were prepared to award mark
point 2 for chlorophyll/chloroplast and mark point 4 for light energy if included in an equation,
provided that the terms 'chlorophyll' and 'light' were written on the arrow and not as a substrate.
Results Plus: Examiner Comments
This candidate was awarded all three marks. The descriptive response covered mark
points 1, 3 and 5 by including photosynthesis, carbon dioxide, water and glucose. The
candidate could have been awarded mark point 4 for talking about light energy at the
end but had already gained the maximum marks available. It should be noted that we
did not like the suggestion that carbon dioxide and water 'reacts with the light energy' at
the beginning of this particular response.
Results Plus: Examiner Comments
Mark points 3 and 5 could be awarded from this equation for identifying that carbon
dioxide and water are the reactants and glucose is also produced. Therefore this
response gained two marks.
Results Plus: Examiner Tip
Food is too vague for glucose (or sugar).
If you are going to use chemical formulae, then they must be completely correct: upper
and lower case letters must be correct and numbers must be subscript. It is safer to
write out the chemical names in full, unless asked to do otherwise.
Q2.
(b)(ii)
This question was poorly answered except by the more able candidates. Many did not quote
values for temperature when giving their description and others tried to explain what was
happening in terms of the transpiration stream.
Results Plus: Examiner Comments
This candidate has looked at the graph and picked out the appropriate temperature
reference but unfortunately has not given their answer in the context of water loss. They
were awarded the third mark point.
Results Plus: Examiner Tip
Candidates should read the question very carefully to ensure they are giving the
information that the examiner has asked for.
Results Plus: Examiner Comments
This was the type of response that we were hoping to get for this question, although the
attempt at an explanation was not necessary. This response was awarded 2 marks.
Results Plus: Examiner Tip
The command word describe requires candidates to say what is happening. Explain is
the command word is used when that we want you to use some Science to say why
something happens.
Results Plus: Examiner Comments
This was very typical of candidates who either forgot or did not realise that values for
the independent variable should be quoted in answers for questions of this type. This
response was awarded 1 mark.
Results Plus: Examiner Tip
Whenever candidates are asked to describe data, either presented in a table or in a
graph, they must quote key values for the independent variable. It is also a good idea to
do a very simple calculation for one of the changes they have described.
(b)(iii)
We saw all the suggestions listed on our mark scheme but very few candidates gave us two
suggestions.
A reference to loss of water from the soil was probably the commonest suggestion made.
Results Plus: Examiner Comments
This question was allocated 2 marks, which indicates that two suggestions are required.
This candidate only gave one suggestion so only 1 mark was awarded.
Results Plus: Examiner Tip
Candidates should use the mark allocation as a guide. They need to make as many
correct statements as there are marks available.
Results Plus: Examiner Comments
This candidate did give us two suggestions. We credited the term 'fair test' but would
have preferred to have seen the term 'valid' used.
Results Plus: Examiner Comments
This was the other common suggestion.
Results Plus: Examiner Tip
Such a simple, single statement is not going to score 2 marks. 2 marks means two facts
are required.
(c)
Candidates coped quite well with this particular question. Predictably, there was confusion
between respiration and photosynthesis but this would not prevent a candidate from being
awarded the other 2 marks if given.
Results Plus: Examiner Comments
This was awarded the first mark but was too vague for any other credit.
Results Plus: Examiner Tip
Candidates should always be as specific as they can. If they know the name of the
process then they must give it.
Results Plus: Examiner Comments
This candidate was awarded the first mark at the end of this response. We were not
crediting a reference to a decrease in glucose levels.
Results Plus: Examiner Tip
Another example where the question must be read carefully, so that the response will
answer the question.
(d)
There were some very good accounts of osmosis, but there was the predictable confusion with
active transport.
Results Plus: Examiner Comments
Ignoring the vague first sentence, this is a good example of the type of response we
were hoping for. This response was awarded 2 marks.
Results Plus: Examiner Comments
Weaker candidates wrote about transport of water through the plant or active transport.
This response failed to gain any marks.
Mark Scheme
Q1.
Answer
(i)
(ii)
(iii)
B
Any two from the
following:
 diffusion (1)
 from an area of
high concentration to
an area of low
concentration/down
a concentration
gradient (1)
 through stoma /
stomata (1)
Any three from the
following:
 (by)
photosynthesis (1)
 ref to chloroplast
/ chlorophyll (1)
 requires carbon
dioxide and water (1)
 light (energy)
needed (for
photosynthesis)(1)
 (to produce)
glucose (1)
Acceptable
answers
Mark
(1)
Accept pores /
between guard cells
Ignore through guard
cells
Ignore incorrect
balancing of
equations throughout
Reject (and)
respiration Accept if
written on arrow in
word / formula
equation Accept
correct formulae
word / formula
equation Accept if
written on arrow in
word / formula
equation Reject
energy is created /
produced Accept
sugar from word /
formula equation
(2)
(3)
Q2.
Answer
(a)
(b)(i)
(b)(ii)
(b)(iii)
(c)
(d)
D - transpiration
B – 32 g
A description
including two of the
following
 it rises between
the temperatures of
15(°C) and 35(°C)
(1)
 water loss
decreases after
35(°C) (1)
 credit correct
reference to figures
from the table, if
related to
temperature (1)
A suggestion
including any two
from the following:
 prevent
evaporation/loss of
water from the soil
(1)
 to ensure that
mass of the calcium
chloride only
changed (due to
water loss from
plant) (1)
 to ensure that
method is valid / it is
a fair test (1)
 to stop the
uptake of water by
the soil (1)
An explanation
including any two
from the following:
 glucose
production will
decrease (1)
 photosynthesis
will decrease (with
increase in
waterloss)(1)
 as water is used
in photosynthesis (1)
A description
including two from
the following:
 osmosis (1)
 from high
concentration to low
Acceptable
answers
Mark
(1)
(1)
ignore any
explanation given,
including ref to
transpiration award
one mark for : water
loss went up and
then went
down eg. greatest
water loss at 35(°C)
there is less water
loss at 45(°C) than at
35(°C)
(2)
ignore ref to water
loss from pot or
roots
ignore
accurate and
reliable
(2)
glucose
production stops
photosynthesis will
stop / is less efficient
accept from a correct
equation
(2)
not active
transport, but ignore
diffusion
correct references to
water potential and
solute potential not
(2)
concentration / down
a concentration
gradient (1)
 through a
partially permeable
membrane (1)
from where there are
more water
molecules
semi permeable
and selectively
permeable