AQA Biology GCSE - Cell Structure

Mark schemes

Q1.
(a) any two from:
• (microscope) slide
• cover slip
• dye / stain
allow named dye / stain
ignore water
• (mounted) needle
• pipette / dropper
• scalpel
ignore knife
• forceps / tweezers
allow swab (to collect cells)
2

(b) eyepiece / lens

do not accept objective lens
1

(c) to focus (the image / cells)

allow to make the cells / image clear(er)
allow to improve resolution (of the
image)
ignore to move the stage up / down
do not accept reference to
magnification
1

(d) any one from:

• no cells in the field of view
• slide not in the correct position
• mirror not in correct position
allow light / microscope not switched on
/ plugged in
• (objective) lens not clicked into place
or
(objective) lens dirty
• (student is) looking at a (large) air bubble
• (the microscope is) not focussed
allow student did not stain the cells
allow idea of magnification not being
high enough
1

(e) Level 2: Scientifically relevant features are identified; the way(s) in

which they are similar/different is made clear and (where appropriate)
the magnitude of the similarity/difference is noted.
4−6

Page 2 of 17
AQA Biology GCSE - Cell Structure

Level 1: Relevant features are identified and differences noted.

1−3

No relevant content
0

Indicative Content

Differences:
• red blood cell has no nucleus or plant cell has a nucleus
• red blood cell has no cell wall or plant cell has a cell wall
• red blood cell is a biconcave disc or there are many different
shapes of plant cell
• red blood cell contains haemoglobin or plant cells do not
contain haemoglobin
• red blood cells do not contain chlorophyll or plant cells (may)
contain chlorophyll
• red blood cell has no chloroplasts or plant cell has chloroplasts
• red blood cell has no (permanent) vacuole or plant cell has
(permanent) vacuole
• red blood cells are (much) smaller than plant cells

Similarities:
both have:
• cytoplasm
• cell membrane
• pigments (although they are different)

ignore references to mitochondria and ribosomes

for Level 2, consideration of both red blood cells and plant cells is
required.

(f) water enters (the cells) by osmosis / diffusion

allow water enters and the cell starts to
swell
ignore explanations of osmosis
1

plant cell has a cell wall (which prevents it from bursting)

allow red blood cell has no cell wall (so
it swells and bursts)
1
[13]

Q2.
(a)

Page 3 of 17
AQA Biology GCSE - Cell Structure

(b) water
in this order only
1

mineral ions
allow minerals / ions
1

energy
1

(c) root hair (cell)

ignore root / hair unqualified
1

(d) large surface / area

allow it has a long projection
allow the walls are thin
allow it has lots of mitochondria
1

(e)

do not accept more than one line from a box on the left
1

(f) nerve (cell)

allow neuron(e)
ignore motor / sensory / relay
1

Page 4 of 17
AQA Biology GCSE - Cell Structure

any one from:

• long
• has branches
• has insulation
allow myelin / fat
1
[10]

Q3.
(a) any two from:
• sterilise equipment / surfaces (before use)
• (use) sterilised agar
ignore ‘clean’ unqualified
ignore wash hands
allow description of how to sterilise
equipment
allow description of how to sterilise agar
• secure lid of the Petri dish with (adhesive) tape
• only lift lid of Petri dish a little (when setting up plate) or lift lid
of Petri dish at an angle (when setting up plate)
2

(b) B

and

it kills the fewest bacteria

or
it has the smallest area where no bacteria were growing
allow it has the smallest clear / white
area
an incorrect answer for one step does
not prevent allocation of marks for
subsequent steps
ignore calculation and subtraction of
filter paper disc area from total area
1

(c) (correct measurement)

Note: In Exampro, the measurement of 1.1 cm or 2.2. cm will

depend on the printing of the exported diagram and
should therefore be checked by the teacher/student using
this mark scheme.

r = 1.1 (cm)
or
r = 11 (mm)
allow d = 2.2 (cm)
or
d = 22 (mm)

Page 5 of 17
AQA Biology GCSE - Cell Structure

allow a tolerance of ±1 mm
1

(recall of the equation)

πr2
1

(calculation/substitution)
3.14 x 1.12
or
3.14 x 112
allow correct calculation / substitution
using an incorrect measurement
1

= 3.799(4) (from 3.14 x 1.12)

or
= 379.9(4) (from 3.14 x 112)
allow 3.8
allow 380
1

correct unit
(3.7994) cm2
or
(379.94) mm2
do not accept unit with no attempt at
working / answer
1

(d) any one from:

• repeat and calculate a mean
• repeat and eliminate anomalies
• use a control disc
allow description of control disc e.g.
disc with water / nothing ignore set up a
control
• use different types of bacteria
1
[9]

Q4.
(a) A
1

(b) chloroplast(s)
ignore chlorophyll
1

(c) guard (cells)

ignore stoma(ta)
1

(d) transpiration stream

Page 6 of 17
AQA Biology GCSE - Cell Structure

ignore transpiration unqualified

1

(e) increased humidity

1

(f) Level 2: Scientifically relevant features are identified; the way(s) in

which they are similar/different is made clear and (where appropriate)
the magnitude of the similarity/difference is noted.
4−6

Level 1: Relevant features are identified and differences noted. 1‒3

1−3

No relevant content.
0

Indicative content:
Structure
• xylem is made of dead cells
and
phloem is made of living cells
• phloem cells have pores in their end walls
and
xylem cells do not have pores in their end walls
• xylem is hollow or xylem does not contain cytoplasm
and
phloem contains cytoplasm
• xylem contains lignin
and
phloem does not (contain lignin)

• both made of cells

• both tubular

Function
• xylem transports water / mineral ions
and
phloem transports (dissolved) sugars
• xylem is involved in transpiration
and
phloem is involved in translocation
• xylem transports unidirectionally
and
phloem transports bidirectionally

• both transport liquids / substances throughout the stem / leaves

/ roots / plant

For Level 2, students must refer to both structure and function of

xylem and phloem tissue.

(g) (correct division)

40 ÷ 7 (in hours)
or
40 ÷ 420 (in minutes)

Page 7 of 17
AQA Biology GCSE - Cell Structure

allow correct answer from student’s

readings throughout
1

5.71 (in hours)

or
0.0952…(in minutes)
allow correct division from incorrect
reading(s) from the tangent
1

(correct conversion to minutes)

0.0952…
allow correct conversion at any point in
the calculation
allow correct conversion of calculated
value to minutes
1

(answer in standard form)

9.5(238) x 10-2
allow correct conversion of calculated
value to standard form
1

(h) (less water loss at night)

allow converse if clearly describing
12:00

stomata are (almost completely) closed

1

(because) it’s cooler / colder

or
(because) there’s less / no light
ignore it’s dark at night
1
[17]

Q5.
(a) bacterium
1

(b) to strengthen the cell

1

(c) chloroplast
1

(d)

Page 8 of 17
AQA Biology GCSE - Cell Structure

additional line from a box on the left negates the mark for that box
3

(e) adjust the focus knob

1

(f) (A =) 15 (mm)
allow a tolerance of ± 1mm
1

(B =) 60 (mm)
1

(g)

allow ecf from question (f)

1

(h)

400
do not accept if a unit is given
1
[12]

Q6.
(a) any two from: (both have)
• cytoplasm
• (cell) membrane
• DNA / genetic material
ignore reference to shape

Page 9 of 17
AQA Biology GCSE - Cell Structure

allow RNA
ignore genetic information
• ribosomes
if no other mark awarded allow
sub-cellular structures for 1 mark
if no other mark awarded allow correct
cellular process, e.g. respiration for 1
mark
2

(b) any three from:

allow converse for eukaryotic cells
allow reference to bacterium instead of
prokaryotic cell
ignore reference to features not shown
in the diagram
• prokaryotic cell is smaller
• prokaryotic cell has no mitochondria
• prokaryotic cell has no nucleus
or DNA is free in the cytoplasm
or genetic material is free in the cytoplasm
if neither mark awarded, allow
prokaryotic cell has no
membrane-bound organelles
ignore genetic information

• prokaryotic cell has a single loop of DNA

or prokaryotic cell has a single loop of genetic material
ignore genetic information

• prokaryotic cell has plasmids

ignore circular / rings of DNA
allow prokaryotic cells have smaller
ribosomes
3

(c) 1 µm = 0.001 mm
or 1 mm = 1000 µm
or 0.05 mm = 50 µm
or 0.05 × 1000
1

(1:) 50
do not accept if a unit is given
1

(d) mitosis
correct spelling only
1

(e) 35%
1

(f) (stage 1)

Page 10 of 17
AQA Biology GCSE - Cell Structure

DNA / chromosomes replicate / duplicate

ignore names of the stages of the cell
cycle
ignore genetic material ignore DNA /
chromosomes double / reproduce
1

mitochondria / ribosomes / sub-cellular structures increase in number

or mitochondria / ribosomes / sub-cellular structures replicate
allow cytoplasm increases
ignore cell grows unqualified
1

(stage 2)
one set of chromosomes is pulled / moved to each end of the cell
allow one of each chromosome is pulled
/ moved to each end of the cell
ignore nucleus divides
1

(stage 3)
the cytoplasm and cell membrane divides (to form two cells)
allow cytoplasm divides and (new) cell
membranes form ignore nucleus divides
1
[13]

Q7.
(a) controls the (activities of the) cell
allow contains genetic information /
genes / DNA / chromosomes
do not accept brain
do not accept controls substances
entering / leaving the cell
1

(b) red blood cell / RBC

allow erythrocyte
ignore blood cell unqualified
ignore platelets
or
bacteria / prokaryote
allow named examples of bacteria
do not accept virus
or
xylem (cell)
1

(c) cell shape is similar to cell in Figure 1 and nucleus present

ignore shading
do not accept a cell wall drawn
1

Page 11 of 17
AQA Biology GCSE - Cell Structure

any two features correctly identified and labelled:

• nucleus
• (cell) membrane
• cytoplasm
• mitochondria / mitochondrion
• ribosome(s)
allow cell wall if drawn and correctly
labelled
do not accept other plant sub-cellular
structures
1

(d) any one from:

• (cellulose cell) wall
• chloroplast
ignore chlorophyll
• (permanent) vacuole
allow starch grain
1

(e)
an answer of (×) 400 scores 3 marks
an answer of (×) 40 scores 2 marks

24 (mm) or 2.4 (cm)

allow in range 23 to 25 (mm) or in
range 2.3 to 2.5 (cm)
1

24
0.06

or

2.4
0.06
allow correct calculation from their
measurement of X to Y in the range 2.3
cm to 3.5 cm or 23 mm to 35 mm
1

(×) 400
allow correct magnification derived from
their measurement in mm
ignore rounding errors
1

(f) high(er) magnification

ignore bigger / zoom
if neither mark awarded allow 1 mark for
see smaller objects or see smaller
sub-cellular structures
1

high(er) resolution or high(er) resolving power

Page 12 of 17
AQA Biology GCSE - Cell Structure

allow see more detail

if neither mark awarded allow 1 mark for
see smaller objects or see smaller
sub-cellular structures
allow 3D image
1
[10]

Q8.
(a)

additional line from a level of

organisation negates the mark for that
level of organisation
2

(b) palisade mesophyll

1

(c)
1

6 / 6.25 / 6.3 (micrometres)

1
an answer of 6 / 6.25 / 6.3 scores 2 marks

(d) they have no chloroplasts / chlorophyll

allow they are underground
allow they don’t get (access to) light
allow (because) photosynthesis needs light
allow they can’t absorb light
ignore ‘sun’
ignore ‘it is dark’
1

(e) differentiation
1

(f) to protect endangered plants from extinction

1

(g) plants can be produced quickly

1

Page 13 of 17
AQA Biology GCSE - Cell Structure

(h) any one from:

• glucose / sugars / starch
• amino acids / protein
• hormones
allow named hormones e.g. auxin
• ions / minerals
allow magnesium / nitrate
• vitamins
allow named vitamins e.g. vitamin B
• water
allow H2O / H2O
ignore oxygen / carbon dioxide / agar / nutrients /
fertiliser
1
[10]

Q9.
(a)
✔ ✔

✔ ✔
1 mark for each correct row if no other marks
awarded allow a mark for one correct column
2

(b) a bacterial cell

1

(c) make / synthesise / produce protein

allow produce enzymes
1

(d) 0.0015 (mm)

allow 1.5 × 10−3 (mm)
1

(e) mitochondria are longer / bigger (than the cell)

allow too big
1

(f)

24
an answer of 16 scores 2 marks
allow 2 × 2 × 2 × 2 or a correct list showing
doubling at each time interval
1

16
allow 90 mins = 8 for 1 mark
1

Page 14 of 17
AQA Biology GCSE - Cell Structure

(g) (number of live cells / bacteria) stays level / the same until 11 hours
answer must refer to number of live cells / bacteria
(not the shape of the graph)
allow (number of cells / bacteria) is very low until 11
hours allow number in the range 10-11 hours
1

then (number of live cells / bacteria) increases rapidly to 2.5 × 108

or
from 11 hours to 14.5 hours
allow (then) increases exponentially
1

then (number of live cells / bacteria) stays at 2.5 × 108

allow (number of live cells / bacteria) stays the
same for the next 5 hours
or
stays the same from 15 to 20.5 hours
if no other mark awarded allow for 1 mark the idea
that the graph is level, then increases, then levels
off again
1

(h) any one from:

• lack of food / nutrients / oxygen / space

or
competition for space

• build-up of toxins
allow ethanol

• temperature too high

1
[12]

Q10.
(a) electron (microscope)
1

(b)
an answer of 150 (μm) scores 2 marks
1

150 (μm)
if answer is incorrect allow for 1 mark sight of 0.015
/ 0.15 / 1.5 / 15
allow ecf for incorrect measurement of line X for
max 1 mark
1
(c) either
large surface area

Page 15 of 17
AQA Biology GCSE - Cell Structure

allow (vacuole contains) cell sap that is more

concentrated than soil water (1)
1

for more / faster osmosis

create / maintain concentration / water potential
gradient (1)

or

allow thin (cell) walls

for short(er) diffusion distance

1

(d) (on hot day) more water lost

allow converse for a cold day if clearly indicated
1

more transpiration
or
more evaporation
1

so more water taken up (by roots) to replace (water) loss (from leaves)
1

(e) (aerobic) respiration occurs in mitochondria

do not accept anaerobic respiration
1

(mitochondria / respiration) release energy

do not accept energy produced / made / created
1

(energy used for) active transport

1

to transport ions, against the concentration gradient

or
from a low concentration to a high concentration
1
[12]

Q11.
(a) nucleus labelled correctly
1

cell membrane labelled correctly

1

(b) mitosis
1

(c) electron (microscope)

Page 16 of 17
AQA Biology GCSE - Cell Structure

(d) higher magnification

1

(e) 45 (mm)
1

45 / 250 or 0.18 (mm)

allow ecf
1

180 (µm)
1
allow 180 (µm) with no working shown for 3 marks

(f) 0.2 µm
1
[9]

Q12.

(a)
extra lines cancel
3

(b) Cell wall

in either order
1

Chloroplast
allow (permanent) vacuole
1
[5]

Page 17 of 17