AQA GCSE Biology Biology Paper 1 (Higher), June 2022: Question 1
17 marks · Standard Demand difficulty · Short Answer
Identify cell structures and functions, and analyze a practical investigation into the effect of salt concentration on potato mass via osmosis.
Practise this questionQuestion
Question text
01 This question is about cells and transport.
01.1 Complete Table 1.
[3 marks]
Table 1
Name of cell part Function of cell part
Contains genetic information
Mitochondria
Controls the movement of substances into and
out of the cell
Cells in potatoes are plant cells.
Cells in potatoes do not contain chloroplasts.
01.2 What is the function of chloroplasts?
[1 mark]
01.3 Name one type of cell in a potato plant that does not contain chloroplasts.
[1 mark]
A student investigated the effect of salt concentration on pieces of potato.
This is the method used.
*03* 1. Cut three pieces of potato of the same size.
2. Record the mass of each potato piece.
3. Add 150 cm3 of 0.4 mol/dm3 salt solution to a beaker.
4. Place each potato piece into the beaker.
5. After 30 minutes, remove each potato piece and dry the surface with a paper towel.
6. Record the mass of each potato piece.
7. Repeat steps 1 to 6 using different concentrations of salt solution.
01.4 What is the independent variable in the investigation?
[1 mark]
Tick ( ) one box.
Concentration of salt solution
Mass of potato piece
Time potato is left in salt solution
Volume of salt solution
01.5 Why did the student dry the surface of each potato piece with a paper towel
in step 5?
[1 mark]
The student calculated the percentage change in mass of each potato piece.
01.6 For one potato piece:
• the starting mass was 2.5 g
• the end mass was 2.7 g.
Calculate the percentage increase in mass of the potato piece.
[2 marks]
Use the equation:
increase in mass
percentage increase in mass = × 100
starting mass
Percentage increase in mass = %
The student used the results from each potato piece to calculate the mean percentage
change in mass at each concentration.
Table 2 shows the results.
Table 2
Concentration of
Mean percentage (%)
salt solution in
3 change in mass
mol/dm
0.0 9.8
0.1 9.5
0.2 7.0
0.3 0.4
0.4 −1.4
01.7 Complete Figure 1.
*05* You should:
• label the x-axis
• use a suitable scale for the x-axis
• plot the data from Table 2
• draw a line of best fit. 7
[4 marks]
Figure 1
01.8 What concentration of salt solution was equal to the concentration of the
solution inside the potato pieces?
Use Figure 1.
[1 mark]
Concentration =8 mol/dm3
01.9 Explain why the potato pieces in the 0.4 mol/dm3 salt solution decreased in mass.
[3 marks]
Mark scheme
Show the mark scheme
Question 1
AO /
Question Answers Extra information Mark
Spec. Ref.
01.1 must be in this order AO1
4.1.1.1
nucleus allow chromosomes 1 4.1.1.2
allow plasmid
(site of aerobic) respiration allow makes ATP 1
or releases energy
do not accept produces / makes
/ creates energy
do not accept anaerobic
respiration
(cell) membrane
AO /
Spec. Ref.
01.2 photosynthesis allow produce glucose / sugar 1 AO1
allow to absorb (sun) light 4.1.1.2
4.4.1.1
ignore contains chlorophyll
AO /
Spec. Ref.
01.3 root (hair) allow xylem / phloem / epidermis 1 AO1
/ meristem 4.1.1.3
4.2.3.1
4.2.3.2
AO /
Spec. Ref.
01.4 concentration of salt solution 1 AO1
4.1.3.2
RPA3
AO /
Spec. Ref.
01.5 to make sure only the potato allow (to) remove excess water 1 AO2
mass was measured / solution / liquid 4.1.3.2
or RPA3
if water / solution / liquid was left do not accept if water / solution
on (the potato), the mass would / liquid was left on (potato) the
be higher / affected mass would be lower
ignore to remove water /
solution / liquid on the outside /
surface (of potato)
AO /
Spec. Ref.
01.6 0.2 2.7 − 2.5 1 AO2
×100 allow ×100
2.5 2.5 4.1.3.2
RPA3
8(%) 1
if no other mark awarded allow 1
mark for
2.5 − 2.7
×100 = − 8 (%)
2.5
AO /
Spec. Ref.
01.7 max 3 marks for bar chart AO2
Mark with 4.1.3.2
01.8 correct scale and axis labelled scale must take up at least 50% 1 RPA3
(concentration (of salt solution) of grid
in mol/dm3)
all points plotted correctly allow a tolerance of ± ½ small 2
square
allow 3 or 4 correct plots for 1
mark
curved line of best fit ignore line extended beyond 1
0.4 mol/dm
ignore line joined point to point
with straight lines
AO /
Spec. Ref.
01.8 correct answer from their line allow a tolerance of ± ½ small 1 AO2
Mark with drawn on Figure 1 square 4.1.3.2
01.7 RPA3
ignore line joined point to point
with straight lines if a line of best
fit is drawn
if no line of best fit is drawn,
allow an answer in the range
0.31 – 0.33 (mol/dm3)
AO /
Spec. Ref.
01.9 allow ‘pieces’ for potato AO2
throughout 4.1.3.2
RPA3
water moves out of cells / potato 1
by osmosis allow by diffusion through a 1
partially / selectively / semi
permeable membrane
(because) the solution in the allow (because) the solution 1
cells / potato is less outside the cells / potato is more
concentrated than outside concentrated than inside
or
(because) the solution in the allow (because) the solution
cells / potato is more dilute than outside the cells / potato is less
outside dilute than inside
allow correct references to water
concentration / potential
ignore reference to amount of
water or salt
do not accept water moves from
an area of high (solute)
concentration to an area of low
(solute) concentration
Total Question 1 17
How to answer it
Cell Biology, Organelles & The Osmosis Required Practical
What This Question Tests
A comprehensive assessment combining core cell biology recall with Required Practical 3 (Investigating Osmosis in Plant Tissue).
- Subcellular structures & functions: Nucleus, mitochondria, cell membrane, and chloroplasts.
- Specialised plant cells: Identifying non-photosynthetic plant tissues (e.g. root hair cells).
- Practical skills & variables: Identifying independent variables and understanding control measures (blotting cylinders dry).
- Mathematical skills: Calculating percentage change in mass and processing negative values.
- Data presentation & analysis: Graph plotting, drawing smooth curved lines of best fit, and determining internal tissue concentration from the x-intercept.
- Scientific explanation: Explaining mass changes using the principles of water potential and osmosis across a partially permeable membrane.
Subcellular Structures and Functions
Completing Table 1 with organelle names and roles
✅ Correct Table Entries
- Contains genetic information → nucleus
- Mitochondria → site of aerobic respiration (or releases energy )
- Controls movement of substances → (cell) membrane
❌ Common Errors & Trap Answers
- "Produces energy" / "Makes energy": Energy cannot be created or destroyed! Examiners strictly reject "makes energy". You must say releases energy.
- Writing anaerobic respiration for mitochondria: Mitochondria are exclusively the site of aerobic respiration.
- Confusing cell wall with cell membrane: Cell walls are freely permeable and provide structural support; the cell membrane controls entry and exit.
Chloroplast Function & Non-Photosynthetic Cells
Understanding why underground plant tissues lack chloroplasts
✅ Correct Answers
01.2: Photosynthesis (also accept: to produce glucose/sugar or absorb light).
01.3: Root hair cell (also accept: root cell, xylem, phloem, epidermal cell).
💡 Key Knowledge
- Chloroplasts contain chlorophyll to absorb light energy for photosynthesis.
- Plant roots grow underground where there is no light, so root cells do not synthesize chloroplasts. Producing them would waste cellular resources and energy.
🧠 Exam Technique
In 01.2, simply writing "contains chlorophyll" scores 0 marks. The question asks for the function (job) of the organelle, not what it contains.
Practical Methodology: Variables & Drying Samples
Required Practical 3 procedural details
✅ Correct Responses
01.4 Independent Variable:
- ☑ Concentration of salt solution [1 mark]
01.5 Drying with paper towel:
- To make sure only the mass of the potato was measured / to remove excess liquid from the outside [1 mark].
🧠 Experimental Variables Refresher
- Independent variable: What you deliberately alter (salt solution concentration).
- Dependent variable: What you measure (change in mass).
- Control variables: What you keep constant (volume of solution, dimensions/surface area of potato, time left in solution).
❌ Common Errors in 01.5
Writing vague statements like "to clean the potato" or "to remove water" will not score. You must specify removing surface/excess water so it does not add false extra mass to the balance.
Percentage Increase Calculation
Step-by-step mass change calculation
📐 Step-by-Step Calculation
Data: Starting mass = 2.5 g, End mass = 2.7 g
- Calculate mass increase:
2.7 g - 2.5 g = 0.2 g - Substitute into given equation:
Percentage increase = (0.2 / 2.5) × 100 - Calculate answer:
0.08 × 100 = 8%
❌ Calculation Pitfalls
- Dividing by the end mass: Always divide by the initial (starting) mass, never the final mass.
- Wrong order of subtraction: If you do (starting - ending), you get a negative value (-8%), which represents a decrease, not an increase.
Graph Skills & Finding Internal Concentration
Plotting points, curved lines of best fit, and reading the intercept
🧠 Graph Criteria (4 Marks Breakdown)
- Axis Label & Scale (1 mark): Label horizontal x-axis with parameter and units: Concentration of salt solution in mol/dm³ . Use an even, linear scale (e.g. 0.0 to 0.4 spanning over 50% of the grid).
- Plotting Points (2 marks): Plot all 5 coordinates accurately to within ±½ small square:
(0.0, 9.8), (0.1, 9.5), (0.2, 7.0), (0.3, 0.4), (0.4, -1.4).
(4 points correct = 1 mark; 5 correct = 2 marks). - Line of Best Fit (1 mark): Draw a single, continuous, smooth curved line passing reasonably close to all points.
✅ 01.8 Intercept Value
Where the curve crosses the horizontal 0.0% line ( y = 0 ), no net movement of water occurs.
Correct value: Read directly from your line of best fit (typically in the range 0.31 – 0.33 mol/dm³ ) [1 mark].
❌ Graph Plotting Traps
- Using a ruler to join dot-to-dot: Osmosis curves are biological curves; straight line zig-zags lose the line mark!
- Missing negative values: The y-axis drops below zero to -2.0%. Ensure point (0.4, -1.4) is accurately plotted below the zero line.
- Forgetting units on axis: Always copy the exact column heading from the table including units ( mol/dm³ ).
Explaining Mass Decrease Using Osmosis
Linking mass change to concentration gradients
✅ Model 3-Mark Explanation
- Movement: Water moves out of the potato cells / tissue. [1 mark]
- Mechanism: By osmosis (or through a partially permeable membrane). [1 mark]
- Reason / Gradient: Because the salt solution outside is more concentrated than the solution inside the potato cells (or the solution inside the cells is more dilute / has a higher water potential). [1 mark]
❌ Major Misconceptions (Examiner Warnings)
- Never say "salt moved": Salt or sugar solute particles are too large to freely move across the partially permeable cell membrane. It is exclusively water that moves.
- Do NOT just say "liquid" or "solution": You must explicitly name water.
- Ambiguous concentration statements: Stating "it is more concentrated" without specifying whether you mean the solution inside the potato or the solution outside will forfeit Mark 3.
💡 The Golden Rule of Osmosis Answers
Always structure 3-mark osmosis explanations with this formula:
[What moves: Water] + [How: Osmosis] + [Why: Direction of concentration gradient]
Topics
Biology · Required Practicals · B1: Cell Biology · Required Practicals
Question and mark scheme from the AQA GCSE Biology examination, Biology Paper 1 (Higher), June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.