BIO AS PAPER 1 2018

Question 1

0 1 . 1 Figure 1 shows part of the blood circulation in a mammal.
Figure 1
Use Figure 1 to give the letter that represents each of these blood vessels.
[3 marks]

Answer 1

D;
G;
F;

Questions 01.1 and 01.2 were designed to assess Assessment Objective 1 and expected recall of
basic knowledge. Question 01.1 allowed students to score well, with just over 50% of them scoring
all three marks, and 93.3% scoring at least one mark. Question 01.2 was less well answered with
only 31.6% of students scoring the mark.

Question 2

0 1 . 2 Name the blood vessels that carry blood to the heart muscle.
[1 mark]

Answer 2

Coronary arteries;

Questions 01.1 and 01.2 were designed to assess Assessment Objective 1 and expected recall of
basic knowledge. Question 01.1 allowed students to score well, with just over 50% of them scoring
all three marks, and 93.3% scoring at least one mark. Question 01.2 was less well answered with
only 31.6% of students scoring the mark.

Question 3

0 1 . 3 Figure 2 box shows a photograph of part of a mitochondrion from a mouse liver cell taken
using a transmission electron microscope at × 62 800 magnification.
Figure 2
Produce a scientific drawing of the mitochondrion in Figure 2 in the box below.
Label the following parts of the mitochondrion on your drawing.
• Matrix
• Crista
[4 marks]

Answer 3

1. No sketched / hanging / crossing lines / shading;
2. Must look similar;
3. Matrix and crista correctly labelled;
4. Correct scale stated (x 62 800);

Question 01.3 tested practical drawing skills that students should have acquired, and there is
guidance for drawing in the practical handbook. This was poorly answered, with just 2.4% scoring
all four marks. Most drawings were sketches, and did not look similar to Figure 2, despite the
question asking students to draw the mitochondrion shown. The question also asked students to
label the matrix and a crista. Very few did, and most did not include a scale of any sort.

Question 4

0 2 . 1 What is a monomer? box

[1 mark

Answer 4

(a monomer is a smaller / repeating) unit /
molecule from which larger molecules /
polymers are made;

02.1 was a question requiring recall of a definition from the specification. Almost 60% of students
gained the mark; those who failed to score only gave the first part of the definition, i.e. it is a small
unit. Many students also used simpler descriptive words, such as ‘building blocks.’

Question 5

0 2 . 2 Lactulose is a disaccharide formed from one molecule of galactose and one molecule
of fructose.
Other than both being disaccharides, give one similarity and one difference between
the structures of lactulose and lactose.
[2 marks]

Answer 5

Similarity
1. Both contain galactose / a glycosidic bond;
Difference
2. Lactulose contains fructose, whereas lactose
contains glucose;

Question 02.2 required a similarity and a difference; students generally performed well with the
similarity, but failed to give a difference, with answers such as “lactulose contains fructose”.
Students must state the actual difference when asked, e.g. lactulose contains fructose but lactose
contains glucose.

Question 6

0 2 . 3 Following digestion and absorption of food, the undigested remains are processed to box
form faeces in the parts of the intestine below the ileum.
The faeces of people with constipation are dry and hard. Constipation can be treated
by drinking lactulose. Lactulose is soluble, but is not digested or absorbed in the
human intestine.
Use your knowledge of water potential to suggest why lactulose can be used to help
people suffering from constipation.
[2 marks]

Answer 6

1. (Lactulose) lowers the water potential of
   faeces / intestine / contents of the intestine;
2. Water retained / enters (due to osmosis)
   and softens the faeces;

Question 02.3 showed that many students do not understand high and low water potentials,
confusing the two. Also, many students thought water moved from the lactulose solution into
faeces, thereby showing a lack of understanding of water movement by osmosis. Only 28.6%
scored two marks.

Question 7

0 3 . 1 Draw box and label a single DNA nucleotide.

[2 marks

Answer 7

1. Phosphate, deoxyribose and base correctly
   labelled;
2. Correct shapes and bonds in the correct
   positions (as shown below);

Question 03.1 required students to draw a diagram that is included in the specification. Just under
half (46.3%) were able to do this successfully. The main issues were bonds drawn in the wrong
place, and the use of the word pentose, rather than deoxyribose. Most were able to recognise that
it was supposed to be a pentagonal molecule

Question 8

3 . 2 Give two features of DNA and explain how each one is important in the
semi-conservative replication of DNA.
[2 marks]

Answer 8

2 1. Weak / easily broken hydrogen bonds between
bases allow two strands to separate / unzip;
2. Two strands, so both can act as templates;
3. Complementary base pairing allows accurate
replication;

Again, 03.2 should have been simple recall of knowledge; however, only 9.2% scored two marks.
Features were simply described and not explained. Students did not give the idea that the
hydrogen bonds between bases were weak or easily broken, and, for mark point 2, most students
said there were two strands, so one acts as a template, rather than both being templates.

Question 9

0 3 . 3 Replication of mitochondrial DNA (mtDNA) is different from that of nuclear DNA. box
The replication of the second strand of mtDNA only starts after two-thirds of the first
strand of mtDNA has been copied.
A piece of mtDNA is 16 500 base pairs long and is replicated at a rate of 50
nucleotides per second.
Tick ( ) the box that shows how long it would take to copy this mtDNA.
[1 mark]

A 330 seconds
B 440 seconds
C 550 seconds
D 660 seconds

Answer 9

32.3% of students scored the mark for question 03.3, with many appearing simply to guess, as
demonstrated by no working appearing on their scripts.
C

Question 10

0 4 Figure box 3 shows part of a prokaryotic cell.
Figure 3
0 4 . 1 Name the structures labelled W to Z in Figure 3.
[2 marks]
W
X
Y
Z

Answer 10

W – (cell surface) membrane
X – cell wall
Y – capsule
Z – flagellum

Questions 04.1 and 04.2 revealed very poor spelling of key terms. 31.7% of students scored two
marks on 04.1 and 16.7% scored two marks on 04.2. Common errors included W and X being
referred to as the inner and outer membranes, and the capsule being labelled as a capsid. In 04.2,
several students gave the functions of the parts, rather than naming the main biological molecule.
For X the most common answer was cellulose

Question 11

4 . 2 Name the main biological molecule in:
[2 marks]
W
X

Answer 11

W - Phospholipids;
X - Murein / glycoprotein;
X - Accept
peptidoglycans.

Question 12

0 4 . 3 Name box the process by which prokaryotic cells divide.
[1 mark

Answer 12

Binary fission;

Question 13

0 5 Figure box 4 represents a triglyceride.
Figure 4
0 5 . 1 Name the molecules represented in Figure 4 by:
[2 marks]
Box P
Box Q

Answer 13

P – glycerol

Q – fatty acid (chains)

Question 14

5 . 2 Name the type of bond between P and Q in Figure 4.

[1 mark]

Answer 14

Ester (bond);

Question 15

0 5 . 3 Describe how you would test a liquid sample for the presence of lipid box and how you
would recognise a positive result.
[2 marks]

Answer 15

1. (Mix / shake sample) with ethanol, then water;
2. White / milky (emulsion)

05.3 was answered fully correctly by nearly half (47.3%) of students. Errors included not adding
water, or adding water first then ethanol, using the word cloudy with no colour and using the word
precipitat

Question 16

0 6 Figure box 5 represents the phylogenetic classification of four different species of fruit fly.
Figure 5
0 6 . 1 Figure 5 shows a hierarchy. Explain how.
[2 marks]

Answer 16

1. (It shows) smaller groups within larger groups /
   larger groups containing smaller groups;
2. With no overlap (between groups);

Students had clearly either learned or not learned what a hierarchy is for 06.1 – just under 60% of
students scored zero.

Question 17

0 6 . 2 Name the taxon to which Drosophilidae belongs.

[1 mark]

Answer 17

Family

with half
getting it correct, and half incorrect. Surprisingly, many students correctly identified the taxonomic
groups, using the letter f, g and s in the diagram, but then failed to convert the “f” into family in their
answer

Question 18

Drosophila box fruit flies display courtship behaviour. One of the stages of courtship is
singing by males. Normally a male will produce a ‘sine song’, in which continual noise
is made, and a ‘pulse song’, in which there is continual noise with some louder peaks.
Scientists showed fruit flies a visual stimulus that made them sing. They made
recordings of these songs.
Figure 6 shows the recordings of the songs of three flies over the same time period.

0 6 . 3 D. erecta and D. willistoni are closely related species but different species.
Describe evidence from Figure 6 that supports this statement.
[2 marks]

Answer 18

1. Sine song is (very) similar / same length (for
   both, so closely related).
2. (But) have different peaks / pulses (in pulse
   song);

Question 06.3 was well answered, with 85.8% of students scoring at least one mark. Errors
included not using Figure 6 as asked, simply stating they are different, but not giving a difference,
and many did not understand what the term frequency means, mistaking it for amplitude.

Question 19

0 6 . 4 The scientists repeated their experiments, using female fruit flies as the visual
stimulus. When a male and female D. willistoni were together, their songs led to
mating.
When two female D.willistoni were together, their songs did not lead to any attempt to
mate.
Use information from Figure 6 to suggest why the two females did not attempt to
mate.
[2 marks]

Answer 19

1. (Three) peaks (in pulse song) occur at the same
   time (since both female) / songs identical / male
   peaks are different;
2. (Therefore) no male (song) to stimulate / cause
   mating;
   OR
   Nothing to stimulate / cause mating;

In question 06.4, only 3.4% of students scored two marks, but 57.1% scored one mark. Mark point
2 was very rarely seen; again, students did not use Figure 6, and did not understand that courtship
is a behaviour that stimulates, causes, or leads to mating. Students mostly stated that the female
‘knew’ that it was another female

Question 20

0 7 . 1 What is the proteome of a cell? box

[1 mark]

Answer 20

(The proteome is the full) range of / number of
different proteins that a cell is able to produce (at a
given time);
OR
(The proteome is the full) range of / number of
different proteins the genome / DNA is able to code
for

Only 17.9% of students scored the mark on 07.1. Although this term is clearly defined in the first
sentence of section 3.4.2 of the specification, few students seem to have learnt it. Wrong answers
were often pure guesses, such as ‘where proteins are stored’ or ‘where tRNA is made’. 13% of
students did not even attempt the question.

Question 21

0 7 . 2 Give two structural differences between a molecule of messenger RNA (mRNA) and
a molecule of transfer RNA (tRNA).
[2 marks]

Answer 21

1. mRNA does not have hydrogen bonds / base
   pairing, tRNA does;
   OR
   mRNA is linear / straight chain, tRNA is
   cloverleaf;
2. mRNA does not have an amino acid binding site,
   tRNA does;
3. mRNA has more nucleotides;
4. (Different) mRNAs have different lengths, all
   tRNAs are similar / same length;
5. mRNA has codons, tRNA has an anticodon;

07.2 was generally well answered; those who failed to score two, once again, did not state a clear
difference, e.g. that “tRNA is clover leaf, but mRNA is linear”. There were also students who
thought tRNA was a double-stranded molecule.

Question 22

0 7 . 3 Starting with mRNA in the cytoplasm, describe how translation leads to the box production
of a polypeptide.
Do not include descriptions of transcription and splicing in your answer.
[5 marks

Answer 22

1. mRNA associates with a ribosome / ribosome
   attaches to mRNA;
2. Ribosome moves to / finds the start codon /
   AUG;
3. tRNA brings / carries (appropriate / specific)
   amino acid;
4. Anticodon (on tRNA complementary) to codon
   (on mRNA);
5. Ribosome moves along to next codon;
   OR
   Ribosome ‘fits’ around two codons / can fit two
   tRNAs;
6. (Process repeated and) amino acids join by
   peptide bonds / condensation reaction (to form
   polypeptide);
   OR
   (Process repeated and) amino acids joined
   using (energy from) ATP (to form polypeptide)

07.3 tested recall, with a specific instruction not to include descriptions of transcription and splicing
in answers. Many did include this, or only discussed this. Only 8.4% of students scored all five
marks. Many described mRNA leaving the cell to associate with a ribosome, and there were many
who also stated that RNA polymerase joins amino acids or forms peptide bonds. Start codon and
first codon were ‘synonyms’ for many students. Overall this question discriminated well.

Question 23

0 8 . 1 State box and explain the property of water that can help to buffer changes in
temperature.
[2 marks]

Answer 23

1. (water has a relatively) high (specific) heat
   capacity;
2. Can gain / lose a lot of heat / energy
   without changing temperature;
   OR
   Takes a lot of heat / energy to change
   temperature;

1. Ignore numbers
relating to heat
capacity
2. Accept due to H
bonding between
water molecules

Answers to 08.1 showed good knowledge, but there was some confusion between heat capacity
and the latent heat of vaporisation. Many students hedged their bets by referring to latent heat
capacity. There were several students who stated that a high heat capacity was caused by strong
hydrogen bonds, or that hydrogen bonds were between H+ and O2– in water, not between water
molecules

Question 24

0 8 . 2 Water is used to hydrolyse ATP.
Name the two products of ATP hydrolysis.
[1 mark]

Answer 24

Adenosine diphosphate and (inorganic)
phosphate

Question 08.2 was well answered; the most common mistake was stating adenine diphosphate
instead of adenosine diphosphate.

Question 25

Hydrolysis of ATP is catalysed by the enzyme ATP hydrolase. box
A student investigated the effect of ATP concentration on the activity of ATP
hydrolase. She used shortening of strips of muscle tissue caused by contraction as
evidence that ATP was being hydrolysed.
• She took four slides A, B, C and D, and added strips of muscle tissue of the same
length to each slide.
• She then added the same volume of ATP solutions of different concentrations to the
four slides and left each slide for five minutes.
• She then recorded the final length of each strip of muscle tissue.
Her results can be seen in Table 1.
Table 1
Slide
Concentration of
ATP solution
added to slide /
×10 6 mol dm 3
Final length of muscle
tissue after
5 minutes / mm
A 2 36
B 4 31
C 6 29
D 8 26
0 8 . 3 Other than those given, name two variables the student should have controlled.
[2 marks]

Answer 25

1. Species / organism the muscle tissue
came from;
OR
Thickness / type / source of the muscle
tissue;
2. Temperature of the muscle tissue / ATP
solution / slides;
3. pH of the ATP solution;

In 08.3 many students did not consider the question and either gave variables whose control had
already been given in the question, or gave unqualified answers of temperature and pH. Only 7%
of students scored two marks. Many also stated the concentration of ATP hydrolase, again
showing a failure to consider the question and realising that this cannot be controlled as it was
produced by the muscle tissue.

Question 26

8 . 4 Describe box and explain the pattern shown by the data in Table 1.
[2 marks]

Answer 26

Description
1. As concentration of ATP increases, length
of muscle decreases;
Explanation
2. More ATP (hydrolysed by ATP
hydrolase), so more energy released, so
more muscle contraction / shortening of
muscle;

In question 08.4, the description was well answered by the majority, however many students
thought the muscle became shortened as the muscle tissue was being hydrolysed. Several also
stated that ATP released more energy for respiration. References to energy being ‘produced’
negated otherwise good responses.

Question 27

0 9 . 1 Describe the pathway taken by an oxygen molecule from box an alveolus to the blood.
[2 marks

Answer 27

1. (Across) alveolar epithelium;
2. Endothelium / epithelium of capillary;

Part 09.1 was not well answered (70.3% scored zero); many students seemingly did not
understand what is meant by pathway and gave the mechanism instead.

Question 28

0 9 . 2 Explain how one feature of an alveolus allows efficient gas exchange to occur.
[2 marks]

Answer 28

1. (The alveolar epithelium) is one cell thick;
2. Creating a short diffusion pathway /
   reduces the diffusion distance;

Question 09.2 asked for an explanation of a feature of an alveolus, not all of the alveoli. Only
23.3% of students scored two marks, the majority giving answers relating to a large surface area.
Those who scored well did have an understanding of a reduced diffusion pathway, but a significant
number involved a “thin membrane” or “one-cell-thick membrane” or “thin epithelium” in their
response

Question 29

Carbon monoxide is a poisonous gas that is present in cigarette smoke. This carbon box
monoxide can be absorbed into the blood where it binds with haemoglobin.
Scientists investigated the concentration of carbon monoxide in cars in which people
were smoking or not smoking. They measured the concentration with the car
windows open and closed. Figure 7 shows the scientists’ results as they presented
them. A value of ± 2 standard deviations from the mean includes over 95% of the
data.
Figure 7
25
25
Turn over ►
IB/M/Jun18/7401/1
Do not write
outside the
0 9 . 3 box In England, in October 2015, a law was introduced making it illegal to smoke in a car
carrying someone who is under the age of 18.
Following the introduction of the law, a politician stated:
‘It is dangerous to smoke when a child is in the car. Higher levels of deadly toxins can
build up, even on short journeys, and children breathe faster than adults, meaning
they inhale more of the deadly toxins.’
Use the information provided and the data in Figure 7 to evaluate the politician’s
statements.
[4 marks]

Answer 29

For
1. Significantly higher concentrations of CO
(compared with no smoking) with closed
window (as no overlap in 2 x SD);
2. Any increase in CO could be dangerous;
OR
CO causes less oxygen to be carried /
provided (which could be deadly in
children);
3. (significantly) higher levels after (just) 5
minutes (with closed windows supporting
short journey statement);
Against
4. No idea if (roughly) 5ppm is ‘deadly’;
5. No significant difference with open window
(as 2 x SD overlaps);
6. No data on child breathing rates;
OR
Idea that children breathe faster but have
smaller lung volume, so overall volume of
CO inhaled could be similar;

09.3 was the question students struggled with the most; only 1.2% scored all four marks. Students
did not use the data provided, and, when they did, appeared not to understand or use the term
significance. Those who used the word simply stated that the ‘data’ or ‘results’ were significant or
not, rather than that the increase or difference was significant. They applied standard, learned
responses without considering the question, such as “no repeats”, even though Figure 7 shows
mean values and standard deviations, i.e. it must have been repeated, “sample size too small”,
“correlation does not mean causation”, and “there may be other factors involved”. Students can
assume that if an experiment or investigation in a question has been completed by scientists, that it
has been completed correctly, unless otherwise stated. There was also a common misconception
that children (and not even their haemoglobin) have a high affinity for oxygen. This question
evoked many lengthy responses that failed to score any marks. Students tended to write a whole
page of raw data comparisons with no conclusions or linger on the same idea for the duration of
their answer, stating the same thing in several different ways. A significant number suggested that
CO from vehicle emissions was also of importance, hence the high levels with an open window
and no smoking. Astute students could see that the CO concentration was significantly and
consistently higher after five minutes of exposure to tobacco smoke when the windows were
closed. Equally, these same students could also analyse the data and notice that the 2 x SD
values for the CO concentrations (when the window was open) overlapped. Therefore, there was
no ‘statistical’ difference with these values. The link between Hb and CO was established by
some, resulting in less oxygen being carried/delivered or provided to tissues. A small minority
appreciated that no evidence/data was available for breathing rates in children. Many students
made reference to breathing rates and lung volume. However, they did not manage to make the
link that smaller lung volume and higher rate could result in similar volumes of CO being inhaled.
Very rarely students questioned whether 5ppm was a deadly level, even though they readily
accepted that CO was dangerous. Equally they failed to establish that any increase in CO
concentration would be dangerou