May/June 2025 Paper 53 Worked Answers (IGCSE Biology 0610 Core)

19 questions · 40 marks · 75 minutes

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1. Question 1(a)(i)

   4 marksDesigning a results table for an enzyme investigation
   Step 1: A results table needs ruled columns with a header line and headings that include units, here the test-tube (or temperature) and the height of foam in mm. Step 2: A foam height must be recorded for all three test-tubes C, R and H so the temperatures can be compared. Step 3: Catalase works faster as the temperature rises towards its optimum, so the cold test-tube C gives a lower foam height than the room-temperature test-tube R.
   Method:

   Recall the features of a good results table, then use enzyme behaviour to predict the trend with temperature.
   Examiner tips

   • Tables need ruled columns, a header line, headings with units, and every measured value.

2. Question 1(a)(ii)

   1 marksDrawing a conclusion about temperature and enzyme activity
   Step 1: More foam means more oxygen, which shows the catalase is breaking down hydrogen peroxide faster. Step 2: The cold tube made the least foam and the warmer tubes made more, so a higher temperature gave more activity. Step 3: The conclusion is that increasing the temperature increases the activity of catalase.
   Method:

   Translate the foam heights into enzyme activity and relate it to the temperature.
   Examiner tips

   • A conclusion links the measured result (foam height) to the variable changed (temperature).

3. Question 1(a)(iii)

   2 marksIdentifying the independent and dependent variables
   Step 1: The independent variable is the one deliberately changed, here the temperature of the test-tubes. Step 2: The dependent variable is the one measured in response, here the height of the foam. Step 3: So temperature is the independent variable and foam height is the dependent variable.
   Method:

   Decide which variable is deliberately changed and which is measured in response.
   Examiner tips

   • Independent = changed; dependent = measured; controlled = kept the same.

4. Question 1(a)(iv)

   1 marksAllowing reactants to reach the test temperature
   Step 1: The investigation tests the effect of temperature, so the contents must be at the water-bath temperature before the reaction begins. Step 2: Leaving the tubes for five minutes lets the hydrogen peroxide warm up or cool down to match the water-bath. Step 3: This means the reaction happens at the intended temperature, making the test fair.
   Method:

   Think about what must be true before the reaction starts in a temperature investigation.
   Examiner tips

   • Reactants are left to equilibrate to the set temperature before the timing begins.

5. Question 1(a)(v)

   1 marksRepeating an investigation to improve reliability
   Step 1: Repeating the investigation produces several readings for each temperature. Step 2: Any reading that does not fit the pattern can be spotted as an anomaly and ignored. Step 3: Using the remaining consistent readings (and their mean) makes the results more reliable.
   Method:

   Think about what extra readings let you do with the data.
   Examiner tips

   • Repeats let you identify anomalies and calculate a reliable mean.

6. Question 1(a)(vi)

   1 marksSafety when preparing potato extract
   Step 1: The hazards are the sharp knife and the grinding action of the pestle. Step 2: Cutting on a tile with the blade moving away from the body keeps the knife away from the hands. Step 3: Keeping the fingers out of the mortar while grinding stops them being crushed by the pestle.
   Method:

   Identify the precaution that keeps the hands clear of the knife and pestle.
   Examiner tips

   • Move the blade and pestle away from your hands and body.

7. Question 1(b)(i)

   3 marksCalculating the volume of a cylinder of foam
   Step 1: The foam is a cylinder, so volume = π × r² × h, and the radius is half the diameter: r = 25 ÷ 2 = 12.5 mm. Step 2: Volume = 3.14 × 12.5² × 29 = 3.14 × 156.25 × 29 = 14228.125 mm³. Step 3: Convert to cm³ by dividing by 1000: 14228.125 ÷ 1000 = 14.228… = 14.2 cm³ to one decimal place.
   Method:

   Find the radius, apply π r² h in mm³, then convert to cm³ and round to one decimal place.
   Examiner tips

   • Halve the diameter to get the radius, square it, and convert mm³ to cm³ by dividing by 1000.

8. Question 1(b)(ii)

   1 marksMeasuring the volume of a gas accurately
   Step 1: Foam height only indirectly indicates the gas, so a method that captures the gas itself is better. Step 2: A gas syringe (or an upturned measuring cylinder over water) collects the oxygen and gives a direct volume reading. Step 3: This measures the volume of oxygen accurately, unlike estimating from the foam.
   Method:

   Choose a method that captures and directly measures the volume of gas.
   Examiner tips

   • Collect a gas in a gas syringe or over water to measure its volume directly.

9. Question 1(c)(i)

   1 marksResult of a positive starch test
   Step 1: Iodine solution is the test for starch. Step 2: When starch is present, the orange-brown iodine turns blue-black. Step 3: So a blue-black colour is a positive result for starch.
   Method:

   Recall the colour change of iodine when starch is present.
   Examiner tips

   • A positive starch test turns iodine blue-black.

10. Question 1(c)(ii)

    1 marksReagent for testing vitamin C
    Step 1: Vitamin C is detected using DCPIP, a blue dye. Step 2: When vitamin C is added, it decolourises the blue DCPIP. Step 3: So DCPIP is the reagent used to test for vitamin C.
    Method:

    Recall which reagent vitamin C decolourises.
    Examiner tips

    • DCPIP is decolourised by vitamin C.

11. Question 1(d)

    6 marksPlanning a photosynthesis investigation
    Step 1: Light intensity is the independent variable, so it must be changed over several values, for example by altering the lamp distance. Step 2: The rate of photosynthesis is measured as the volume of oxygen produced in a fixed time, the dependent variable. Step 3: The temperature, plant species and carbon dioxide concentration are kept constant and the readings repeated; only the first plan does all of this.
    Method:

    Check each plan changes only the light intensity, measures oxygen output and is repeated.
    Examiner tips

    • A valid plan changes one variable, measures a relevant response, controls the rest and repeats.

12. Question 2(a)(ii)

    3 marksCalculating actual size from magnification
    Step 1: Rearrange magnification = length of PQ ÷ actual length to give actual length = length of PQ ÷ magnification. Step 2: Actual length = 84 ÷ 3.4 = 24.7… mm. Step 3: To two significant figures this is 25 mm.
    Method:

    Rearrange the magnification formula, divide 84 by 3.4 and round to two significant figures.
    Examiner tips

    • actual length = image length ÷ magnification.

13. Question 2(a)(iii)

    2 marksComparing acorns of two oak species
    Step 1: A valid difference is a visible feature that is not the same in both acorns. Step 2: The Turkey oak acorn has a flatter nut top, while the Caucasian oak has a rounded one. Step 3: The Turkey oak cupule has spines, while the Caucasian oak cupule is smooth, giving two correct differences.
    Method:

    Compare the nut top and the cupule of each acorn to find two genuine differences.
    Examiner tips

    • Differences must be visible features that are not the same in both specimens.

14. Question 2(b)(i)

    2 marksControlling variables in a germination investigation
    Step 1: A factor kept constant is one that is the same for every pot. Step 2: All the acorns were grown in the same type of soil and at the same temperature of 25 °C. Step 3: So the type of soil and the temperature are two controlled factors.
    Method:

    Pick the conditions that were the same for all three species.
    Examiner tips

    • Controlled factors are the conditions kept the same for every group.

15. Question 2(b)(ii)

    4 marksPlotting a bar chart with a key
    Step 1: Both axes are labelled with units and a suitable, even scale is chosen so the bars fill more than half the grid. Step 2: All six bars (mean mass and proportion germinated for each of the three species) are plotted accurately with gaps between the species. Step 3: A key identifies which bars show the mean mass and which show the proportion germinated.
    Method:

    Recall the rules for a bar chart with two datasets and pick the approach that meets all of them.
    Examiner tips

    • Bar charts need labelled axes with units, an even scale, gaps between bars and a key for multiple datasets.

16. Question 2(b)(iii)

    1 marksUsing a large sample size
    Step 1: Individual acorns vary, so a few might not represent the species. Step 2: Measuring 100 acorns gives a large, representative sample. Step 3: This reduces the effect of variation between individuals and avoids bias, so the trend is more reliable.
    Method:

    Think about how the sample size affects how representative the results are.
    Examiner tips

    • Large samples are more representative and reduce the effect of variation.

17. Question 2(b)(iv)

    1 marksCalculating percentage water content
    Step 1: Water lost = initial mass − dried mass = 1.96 − 0.74 = 1.22 g. Step 2: Percentage water content = (water lost ÷ initial mass) × 100 = (1.22 ÷ 1.96) × 100. Step 3: This gives 62.24… = 62.2 %.
    Method:

    Find the mass of water lost, divide by the initial mass and multiply by 100.
    Examiner tips

    • Percentage water content = (mass of water lost ÷ initial mass) × 100.

18. Question 2(c)

    1 marksReagent for testing for protein
    Step 1: Protein is detected using biuret solution. Step 2: When protein is present, the blue biuret solution turns purple (lilac). Step 3: So biuret solution is the reagent used to test for protein.
    Method:

    Recall which reagent changes colour with protein.
    Examiner tips

    • Biuret solution turns purple with protein.