OCR GCSE Biology A: Practical skills I: microscopy, food tests, sampling and enzyme practicals (PAG 1-4) (J247) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions follow Topic B7, Practical skills, of the OCR GCSE (9-1) Gateway Science Biology A (J247) specification, Version 4.0 (August 2026): practical activity groups (PAGs) 1 to 4 and working scientifically skills 2a to 2d. No Higher Tier only statements appear here. Read the study guide and revision notes first, and see the OCR GCSE Biology hub, the printable checklist and the free 10-minute diagnostics.

Questions

1. A root tip cell is 42 mm long in a photomicrograph. Its actual length is 70 µm. Calculate the magnification of the photomicrograph. [3]

2. Describe how to make and view a temporary slide of onion epidermis. [4]

3. State three features of a good labelled scientific drawing of cells. [3]

4. A food sample is tested. Iodine solution stays orange-brown, Benedict’s reagent stays blue after heating, biuret reagent turns purple and the ethanol test gives a clear liquid.

(a) Identify the biological molecule present and give the evidence. [2] (b) Describe how to carry out the Benedict’s test safely. [3]

5. A student investigates amylase digesting starch using continuous sampling.

(a) Describe how the end point is found. [3] (b) The end point is reached at 270 s. Calculate the rate as 1 ÷ time, to 2 significant figures. [1]

6. A lawn of area 80 m² is sampled with a 0.25 m² quadrat for daisies.

(a) Describe how to place the quadrats randomly. [2] (b) Counts in eight quadrats were 2, 7, 4, 0, 5, 3, 6 and 1. Estimate the number of daisies on the lawn. [3]

7. In a pond, 30 beetles are caught, marked and released. A second sample has 40 beetles, of which 8 are marked.

(a) Estimate the population. [2] (b) State two assumptions made. [2]

8. A transect runs from a hedge across a field. At 2 m intervals from 0 m to 10 m, light intensity was 300, 900, 1800, 2900, 3800 and 4100 lux, and moss plants per quadrat were 14, 11, 7, 4, 2 and 1.

(a) Describe how moss numbers change with distance from the hedge. [1] (b) State the relationship between light intensity and moss numbers. [1] (c) Explain why the data do not prove that light intensity affects moss. [1] (d) Suggest one other abiotic factor to measure and how. [1] (e) Suggest one improvement to make the results more representative. [1]

9. Catalase is added to hydrogen peroxide. Oxygen volumes were 0, 14, 25, 33, 38, 40 and 40 cm³ at 0, 20, 40, 60, 80, 100 and 120 s.

(a) Calculate the initial rate over the first 20 s, with units. [2] (b) Calculate the rate between 60 s and 80 s. [1] (c) Explain why the rate decreases and reaches zero. [2] (d) Name apparatus that measures the gas volume more precisely than a measuring cylinder in a trough. [1]

10. Times for iodine to stop turning blue-black with amylase at five temperatures (three repeats each): 20 °C: 124, 118, 121 s; 30 °C: 66, 64, 68 s; 40 °C: 35, 150, 33 s; 50 °C: 52, 50, 54 s; 60 °C: no change in 300 s.

(a) Pick out the odd result and find the mean time at 40 °C without it. [2] (b) Calculate 1 ÷ mean time at 30 °C, to 2 significant figures. [1] (c) State the best estimate of the optimum temperature and how to improve it. [2] (d) Explain the result at 60 °C. [2]

11. A potometer bubble moves 36 mm in 5 minutes along a capillary of radius 0.6 mm.

(a) Calculate the volume of water taken up, in mm³ to 3 significant figures. [3] (b) Calculate the rate in mm³ per minute, to 2 significant figures. [1] (c) Explain why the shoot is cut under water. [2]

12. Plan an investigation of how pH affects amylase breaking down starch, using a colour change to follow the reaction. Include variables, apparatus, safety and how you would present results. [9]

Answers

1. 42 mm = 42 000 µm [1]. magnification = image size ÷ actual size = 42 000 ÷ 70 [1]. ×600 [1]. [3] Examiner insight: Writing the formula and converting to one unit before dividing is what keeps a magnification answer from being off by a factor of 1000.

2. Lay a thin piece of epidermis flat on a drop of water or stain on a slide [1]. Lower a cover slip slowly from one edge so no air is trapped [1]. Begin on the shortest objective and use the large then the small focus wheel [1]. Centre the specimen before changing to a longer objective [1]. [4] Examiner insight: A four-mark description needs four distinct actions in order; “put it under the microscope” alone adds little.

3. Any three of: sharp pencil, single clear lines and no shading [1]; ruled labels that end on the structure and never intersect [1]; title with magnification or a scale bar [1]; large and in proportion. [3] Examiner insight: Vague words such as “neat” are less useful than a specific, checkable feature.

4. (a) Protein [1], because biuret gave purple while the others were negative [1]. [2] (b) Place the sample and Benedict’s reagent in a boiling tube [1]. Heat in a hot water bath, not directly in a flame, wearing eye protection and using a holder [1]. Look for a colour change from blue and compare it with a colour chart [1]. [3] Examiner insight: Give both the result and the reason; a bare “protein” answer leaves out the evidence the question asks for.

5. (a) Put drops of iodine in a spotting tile [1]. Every 30 s move a drop of the reaction mixture into a fresh well [1]. The end point is the time when the iodine stays orange-brown, showing no starch [1]. [3] (b) 1 ÷ 270 = 0.0037 s⁻¹ [1]. [1] Examiner insight: Say what the colour shows, not just “it changes colour”, and give the unit with a rate.

6. (a) Mark a grid with two tape measures [1]. Use random numbers as the coordinates for each quadrat [1]. [2] (b) Total = 28, mean = 28 ÷ 8 = 3.5 per quadrat [1]. 3.5 ÷ 0.25 = 14 per m² [1]. 14 × 80 = 1120 daisies [1]. [3] Examiner insight: Show each stage of the scaling up; showing each stage lets a marker see where a slip happened.

7. (a) 30 × 40 = 1200 [1]. 1200 ÷ 8 = 150 beetles [1]. [2] (b) Any two of: marks do not harm or wash off [1]; marked beetles mix back with the population [1]; no births, deaths or migration in the period. [2] Examiner insight: Assumptions must be about the method; “the count was accurate” is too general.

8. (a) Moss numbers fall as distance from the hedge increases [1]. [1] (b) As light intensity increases, moss numbers decrease (a negative correlation) [1]. [1] (c) Other factors, such as soil moisture, also change along the transect, so correlation does not show cause [1]. [1] (d) Soil moisture, using a moisture meter at each quadrat (or soil pH with a probe) [1]. [1] (e) Repeat the transect or add more quadrats at each distance [1]. [1] Examiner insight: Quote the data, with direction and trend, rather than saying “it changes”.

9. (a) 14 ÷ 20 [1] = 0.70 cm³/s [1]. [2] (b) (38 − 33) ÷ 20 = 0.25 cm³/s [1]. [1] (c) Substrate is used up, so its concentration falls [1]; fewer collisions with active sites, and the rate is zero when no substrate remains [1]. [2] (d) Gas syringe [1]. [1] Examiner insight: Link the rate change to substrate concentration; saying the enzyme “gets tired” does not explain it.

10. (a) 150 s does not fit the pattern [1]. Mean = (35 + 33) ÷ 2 = 34 s [1]. [2] (b) Mean at 30 °C = 66 s; 1 ÷ 66 = 0.015 s⁻¹ [1]. [1] (c) About 40 °C, the shortest time [1]. Test more temperatures between 30 °C and 50 °C, such as 35 °C and 45 °C [1]. [2] (d) High temperature breaks bonds and changes the shape of the active site [1]. The substrate no longer fits, so the enzyme is denatured and starch is not digested [1]. [2] Examiner insight: Exclude the anomaly before averaging, and say that you have done so.

11. (a) Area = π × 0.6² = 1.131 mm² [1]. Volume = area × length = 1.131 × 36 [1]. 40.7 mm³ [1]. [3] (b) 40.7 ÷ 5 = 8.1 mm³ per minute [1]. [1] (c) Cutting under water stops air entering the xylem [1]. Air would break the water column and stop uptake, so the bubble would not reflect water uptake [1]. [2] Examiner insight: Use the unrounded volume in the next step and round only at the end.

12. Any nine of: independent variable is pH, using buffer solutions at several pH values [1]; dependent variable is time for starch to disappear, found with iodine [1]; use continuous sampling every 30 s on a spotting tile [1]; keep temperature constant in a water bath [1]; same volume and concentration of amylase and starch [1]; repeat each pH and calculate a mean, leaving out anomalies [1]; safety: eye protection, avoid iodine on skin and take care with hot water [1]; table with pH in the first column and units in headings [1]; graph with pH on the x-axis and rate (1 ÷ time) on the y-axis [1]. [9] Examiner insight: Cover variables, method, safety and presentation; long answers that leave out controls are less complete.

Where marks are usually lost

• Not converting mm to µm before dividing in magnification questions.
• Naming a test result without the starting colour or the heating step.
• Heating Benedict’s directly in a flame in a description.
• Writing “random” for quadrat placement without saying how.
• Forgetting to multiply the mean per m² by the total area.
• Treating a correlation as proof of cause.
• Leaving out units from rates, such as cm³/s.
• Including an anomalous result in a mean.
• Not saying how variables were controlled.

Next steps

• Study guide
• Revision notes
• OCR GCSE Biology hub and printable checklist
• All free 10-minute diagnostics
• Book a free trial class

Official syllabus

OCR, GCSE (9-1) Gateway Science Suite Biology A (J247), Version 4.0 (August 2026), for first assessment in 2018: Topic B7 Practical skills (PAG 1 to PAG 4) and working scientifically skills 2a to 2d.