IGCSE Biology 0610/52 October/November 2025 Past Paper with Answers

Question 1

In an investigation into the rate of respiration in yeast, a 1% and a 4% glucose solution are each mixed with yeast and the final height of the yeast in the large test-tube is measured after five minutes in a waterbath. Which option describes a correct results table and the expected pattern of the results?

1. a ruled table with a header line and headings that include the unit for height, recording the final height for both the 1% and the 4% glucose tubes, with the 4% tube giving the greater height
2. a ruled table that records the final height for both the 1% and the 4% tubes but gives no units in any of its headings, with the 1% tube giving the greater height instead
3. a table that records only the colour of the yeast in each tube, with neither the final heights nor any units written into the headings of the table
4. a single column listing the final height for the 4% glucose tube only, leaving the 1% glucose tube out of the table completely

Question 2

In the yeast investigation the 4% glucose tube gave a greater height than the 1% glucose tube in the same time. What is the correct conclusion about the effect of glucose concentration on the rate of respiration in the yeast?

1. the higher the concentration of glucose solution, the greater the rate of respiration in the yeast
2. the higher the concentration of glucose solution, the lower the rate of respiration in the yeast
3. the concentration of glucose solution has no effect on the rate of respiration in the yeast
4. the yeast only respires when there is no glucose solution present at all

Question 3

In the yeast respiration investigation the glucose concentration is deliberately changed and the height of the yeast in the large test-tube is measured. Which option correctly identifies the independent and the dependent variable?

1. the independent variable is the concentration of the glucose solution and the dependent variable is the height of the yeast in the large test-tube
2. the independent variable is the height of the yeast in the large test-tube and the dependent variable is the concentration of the glucose solution
3. the independent variable is the temperature of the waterbath and the dependent variable is the concentration of the glucose solution
4. the independent variable is the volume of yeast added and the dependent variable is the time spent in the waterbath

Question 4 · Answer A

Step 1: Hot water in an open waterbath cools down over time, so the temperature would drift. Step 2: A thermostatically controlled waterbath senses the temperature and heats the water to hold it steady. Step 3: So using a thermostatically controlled waterbath keeps the temperature constant.

Question 5 · Answer A

Step 1: The height is read off a ruler held against the test-tube. Step 2: If the top of the yeast is uneven or has bubbles, it is hard to decide exactly where to read the height. Step 3: This uncertainty in the reading is a genuine source of error.

Question 6 · Answer A

Step 1: The glucose in the final mixture must give 3% in 5 cm³, which is the same amount of glucose as in 3 cm³ of the 5% solution (5 × 3 = 15 = 3 × 5). Step 2: So 3 cm³ of 5% glucose solution is needed. Step 3: The total volume is 5 cm³, so the distilled water is 5 − 3 = 2 cm³.

Question 7 · Answer A

Step 1: Reducing sugars are tested for using Benedict's solution. Step 2: The sample is mixed with Benedict's solution and then heated in a hot waterbath. Step 3: Iodine tests for starch, biuret for protein and ethanol for fats, so only the Benedict's-and-heat method tests for a reducing sugar.

Question 8 · Answer A

Step 1: In the emulsion test the food is mixed with ethanol and then added to water. Step 2: If fat is present, it forms tiny droplets that make the mixture look cloudy and white. Step 3: A blue-black colour is the starch result, purple is the protein result and brick-red is the reducing-sugar result, so the fat result is the cloudy white emulsion.

Question 9 · Answer A

Step 1: Ethanol is highly flammable and its vapour can catch fire easily. Step 2: So it must be kept away from any flames, burners or other sources of heat. Step 3: Heating it in a flame or leaving it near the hot waterbath would be dangerous, and saying no precautions are needed is wrong.

Question 10 · Answer A

Step 1: To test exercise intensity, the intensity is changed while the same person and conditions are kept constant. Step 2: The heart rate is measured after each exercise and allowed to return to resting before the next one. Step 3: Repeating each exercise and including a safety precaution makes the plan reliable and safe, which only the first method does.

Question 11 · Answer A

Step 1: A biological drawing uses single, clear, continuous lines with no shading or colouring. Step 2: It should be large, drawn bigger than the original photograph. Step 3: It must show the observed features: the five arms, an enclosed central shape that does not touch the edges, and where the colour changes on each arm.

Question 12 · Answer A

Step 1: Rearrange magnification = photograph length ÷ actual diameter to give actual diameter = photograph length ÷ magnification. Step 2: Actual diameter = 93 ÷ 0.32 = 290.6 mm. Step 3: To two significant figures this is 290 mm.

Question 13 · Answer A

Step 1: The spiny starfish is covered in spines and has a pale, bright centre, while the necklace starfish is smooth and has a dark centre, so these are two genuine differences. Step 2: Both animals have five arms, which is a real similarity. Step 3: The other options reverse the features, invent wrong numbers of arms or deny the central disc, so they are incorrect.

Question 14 · Answer A

Step 1: To compare counts fairly, the area sampled at each depth must be the same size, here 20 m². Step 2: Taking all the photographs on the same day in July keeps the time of year the same, so seasonal changes do not affect the comparison. Step 3: Different-sized areas, different days or inconsistent counting would all make the comparison unfair.

Question 15 · Answer A

Step 1: Both axes are labelled with their units, here depth in m and number of starfish, and a linear scale is chosen so the data fill more than half the grid. Step 2: All five counts are plotted accurately. Step 3: The bars are drawn the same width with no gaps between them, which is what makes it a histogram.

Question 16 · Answer A

Step 1: The depth range with the most starfish is the one with the largest count. Step 2: The counts are 337, 1486, 1243, 241 and 121, and the largest of these is 1486. Step 3: The count of 1486 belongs to the 10.0 to 19.9 m range, so most starfish were found there.

Question 17 · Answer A

Step 1: The total is 337 + 1486 + 1243 + 241 + 121 = 3428 starfish. Step 2: The percentage in the 0.0 to 9.9 m range is (337 ÷ 3428) × 100 = 9.83…%. Step 3: As a whole number this rounds to 10%.