2025 Cambridge IGCSE Biology (0610) Practice Paper with Answers

The table shows two examples of immunity. Which row correctly classifies these types of immunity?

| Row | Receiving antibodies through breast milk | Producing memory cells after an infection |
| :--- | :--- | :--- |
| A | active | active |
| B | active | passive |
| C | passive | active |
| D | passive | passive |

The list shows some changes that occur in the thorax during ventilation:

1. The diaphragm contracts and flattens.
2. The internal intercostal muscles contract.
3. The volume of the thorax increases.
4. The pressure inside the lungs increases.

Which changes occur during inspiration (breathing in)?

During genetic modification, a human gene is inserted into a bacterial plasmid. Which enzymes are used to cut the DNA and to join the DNA fragments together?

| Row | Enzyme used to cut DNA | Enzyme used to join DNA fragments |
| :--- | :--- | :--- |
| A | protease | lipase |
| B | restriction enzyme | DNA ligase |
| C | DNA ligase | restriction enzyme |
| D | restriction enzyme | protease |

What is the effect of a temperature of 60 °C on the activity of a human digestive enzyme?

A plant cell with a water potential of -300 kPa is placed in a concentrated sucrose solution with a water potential of -600 kPa. Which statement describes what happens to the cell?

Which adaptive feature is correctly matched with its function in a xerophyte?

Which process in the nitrogen cycle converts ammonium ions into nitrate ions?

Albinism in humans is inherited as an autosomal recessive trait. Two parents with normal skin pigmentation have an albino child. What is the probability that their next child will also be albino?

Plant cells are placed in a concentrated sucrose solution. Which row correctly describes the changes to the cell’s state?

The rate of an enzyme-catalysed reaction was measured at different substrate concentrations. At high substrate concentrations, the rate of reaction remains constant even if more substrate is added. What is the reason for this?

Which statement correctly describes passive immunity?

How does the thin layer of water lining the alveoli assist in gas exchange?

During the genetic modification of bacteria to produce human proteins, which enzyme is used to join the useful human gene into a cut bacterial plasmid?

In a species of plant, allele \(F^R\) produces red flowers and allele \(F^W\) produces white flowers. The heterozygous genotype \(F^R F^W\) produces pink flowers. If two pink-flowered plants are crossed, what is the expected ratio of phenotypes in the offspring?

Which feature is an adaptive feature of a hydrophyte?

Which process in the nitrogen cycle converts ammonium ions into nitrate ions in the soil?

The table shows the changes in mass of four different plant tissues, P, Q, R and S, after being placed in a beaker containing a 0.5 mol/dm³ sucrose solution for two hours.

$$\begin{array}{|c|c|c|} \hline \text{Tissue} & \text{Initial mass / g} & \text{Final mass / g} \\ \hline P & 2.5 & 2.1 \\ \hline Q & 2.5 & 2.5 \\ \hline R & 2.5 & 2.9 \\ \hline S & 2.5 & 3.2 \\ \hline \end{array}$$

Which tissue had the highest water potential before being placed in the sucrose solution?

In humans, the allele for a certain genetic condition is recessive. A couple, both of whom do not have the condition, have three children. Their first child has the condition, while the next two do not. What is the probability that their fourth child will be heterozygous for the condition?

Which statement correctly describes passive immunity?

An enzyme-catalysed reaction was investigated at different temperatures. The table shows the rate of reaction at each temperature.

$$\begin{array}{|c|c|} \hline \text{Temperature / } ^\circ\text{C} & \text{Rate of reaction / arbitrary units} \\ \hline 10 & 12 \\ \hline 20 & 25 \\ \hline 30 & 50 \\ \hline 40 & 85 \\ \hline 50 & 10 \\ \hline 60 & 0 \\ \hline \end{array}$$

Which statement explains the change in the rate of reaction between 40 °C and 50 °C?

Which row in the table correctly describes the state of the diaphragm and external intercostal muscles, as well as the movement of the ribcage, during quiet breathing out (expiration)?

$$\begin{array}{|c|c|c|c|} \hline \text{Row} & \text{Diaphragm} & \text{External intercostal muscles} & \text{Ribcage movement} \\ \hline \text{A} & \text{contracts} & \text{contract} & \text{upwards and outwards} \\ \hline \text{B} & \text{contracts} & \text{relax} & \text{downwards and inwards} \\ \hline \text{C} & \text{relaxes} & \text{contract} & \text{upwards and outwards} \\ \hline \text{D} & \text{relaxes} & \text{relax} & \text{downwards and inwards} \\ \hline \end{array}$$

Choose the correct row (A, B, C or D).

Some features of plants are listed below:

1. Thick waxy cuticle
2. Stomata on the upper epidermis of leaves
3. Large air spaces in tissues
4. Deep, extensive root systems

Which of these features are typical adaptations of hydrophytes (plants living in wet or aquatic environments)?

What are the roles of restriction enzymes and DNA ligase in the production of genetically modified bacteria?

The sequence of transitions below represents part of the nitrogen cycle:

$$\text{Organic nitrogen compounds in dead plants} \xrightarrow{1} \text{Ammonium ions} \xrightarrow{2} \text{Nitrate ions} \xrightarrow{3} \text{Nitrogen gas}$$

Which row correctly identifies the biological processes represented by 1, 2 and 3?

$$\begin{array}{|c|c|c|c|} \hline \text{Row} & \text{Process 1} & \text{Process 2} & \text{Process 3} \\ \hline \text{A} & \text{decomposition} & \text{nitrification} & \text{denitrification} \\ \hline \text{B} & \text{nitrification} & \text{denitrification} & \text{nitrogen fixation} \\ \hline \text{C} & \text{decomposition} & \text{denitrification} & \text{nitrification} \\ \hline \text{D} & \text{nitrogen fixation} & \text{nitrification} & \text{denitrification} \\ \hline \end{array}$$

Choose the correct row (A, B, C or D).

A plant cell with a water potential of -300 kPa is placed in a solution with a water potential of -700 kPa. Which row correctly describes the net movement of water and the state of the cell after a few hours?

A student set up four test-tubes containing starch solution and amylase at different temperatures. The time taken for the starch to be completely broken down was recorded: Tube 1 (15 degrees C) took 15 minutes, Tube 2 (25 degrees C) took 8 minutes, Tube 3 (35 degrees C) took 3 minutes, and Tube 4 (45 degrees C) took 12 minutes. At which temperature did the amylase have the highest rate of activity?

Which statement correctly describes passive immunity?

The composition of four different gases in inspired and expired air is compared. Which gas has a percentage of approximately 0.04% in inspired air and 4.0% in expired air?

In genetic modification, which enzymes are used to cut a specific gene from human DNA and to join it into a bacterial plasmid?

Albinism is an inherited condition caused by a recessive allele, a. The dominant allele, A, results in normal skin pigmentation. Two parents with normal skin pigmentation have an albino child. What is the probability that their next child will also be albino?

Which leaf feature is an adaptation of a xerophytic plant to reduce the rate of transpiration?

Which biological process in the nitrogen cycle converts ammonium ions into nitrate ions?

A patient is bitten by a venomous snake and is immediately injected with an antivenom containing antibodies. Three months later, they are bitten by the same species of snake. Why is the patient not protected from the venom during the second bite?

Which physiological changes occur in the human thorax during inspiration?

Which row correctly identifies the roles of restriction enzymes and DNA ligase in genetic modification?

Which statement describes what happens to an enzyme when it is heated slightly above its optimum temperature, but not completely denatured?

Plant cells are placed in a concentrated salt solution. Which description of the state of the cells and the direction of water movement is correct?

Which adaptation of a xerophytic plant is correctly matched with how it helps the plant survive in dry conditions?

In the nitrogen cycle, which process converts ammonium ions into nitrate ions?

A father has blood group AB and a mother has blood group O. What is the probability that their first child will have blood group A?

Table 1.1 shows the ventilation rate and tidal volume of an athlete at rest and during two different intensities of running.

Table 1.1
| State | Ventilation rate / breaths per minute | Tidal volume / \(dm^3\) |
| :--- | :---: | :---: |
| Rest | 12 | 0.5 |
| Moderate running | 24 | 1.8 |
| Maximum sprinting | 40 | 2.5 |

(a) (i) Calculate the minute ventilation (volume of air breathed in one minute) during moderate running. Show your working and state the unit. [3]

(a) (ii) State and explain how the change in tidal volume during exercise supports the increased rate of aerobic respiration in muscle cells. [3]

(b) Describe how ciliated cells and goblet cells work together to protect the gas exchange system from pathogens during exercise. [4]

(c) Explain the role of the internal and external intercostal muscles during expiration during intense exercise. [3]

Cholera is a transmissible disease caused by a bacterium. It results in severe diarrhoea.

(a) Explain how the cholera bacterium causes diarrhoea. [4]

(b) Explain why treatment with oral rehydration therapy (ORT) is highly effective, and state what it consists of. [3]

(c) Compare active immunity, such as that gained from a cholera vaccine, with passive immunity, such as that a newborn receives from breast milk. [6]

A student investigated the effect of temperature on the rate of starch breakdown by the enzyme amylase. The results are shown in Table 3.1.

Table 3.1
| Temperature / \(^\circ C\) | Rate of starch breakdown / arbitrary units |
| :---: | :---: |
| 10 | 1.2 |
| 20 | 3.5 |
| 30 | 7.8 |
| 40 | 12.4 |
| 50 | 4.1 |
| 60 | 0.0 |

(a) Describe and explain the trend shown by the data from \(10^\circ C\) to \(40^\circ C\). [4]

(b) Explain the results obtained at \(50^\circ C\) and \(60^\circ C\). [4]

(c) Suggest how the student could modify the experiment to obtain a more precise estimate of the optimum temperature for this amylase. [2]

(d) State the names of the substrate and product of the reaction catalysed by amylase, and name the reagent used to test for the presence of the product. [3]

Albinism is an inherited condition in rabbits where they lack pigment in their fur and eyes. It is caused by a recessive allele, \(a\). The dominant allele, \(A\), results in normal pigmentation.

(a) Define the terms:
(i) genotype [1]
(ii) homozygous [1]

(b) Two rabbits with normal pigmentation were mated. They produced a litter of seven offspring: five had normal pigmentation and two were albino.
(i) State the genotypes of the parents. Explain your choice. [3]
(ii) Complete a genetic diagram to show the possible genotypes and phenotypes of the offspring from this cross. [5]
(iii) Calculate the probability that the next offspring produced by these parents will be a male rabbit with normal pigmentation. Show your working. [4]

Human growth hormone (HGH) can be produced on an industrial scale using genetically modified bacteria grown in fermenters.

(a) Describe how a gene, such as the one for HGH, is isolated from a human cell and inserted into a bacterial plasmid. [6]

(b) State three reasons why bacteria are useful organisms for biotechnology and genetic modification. [3]

(c) Fermenters are used to grow the genetically modified bacteria. Explain the importance of maintaining the following conditions inside a fermenter:
(i) a constant temperature [2]
(ii) constant agitation (stirring) of the mixture [3]

Nitrogen is an essential element for all living organisms. Four major processes in the soil nitrogen cycle are described below:
- Process P: Atmospheric nitrogen gas is converted directly to ammonium ions in the soil.
- Process Q: Ammonium ions are converted to nitrate ions.
- Process R: Nitrate ions are absorbed by plant roots.
- Process S: Nitrate ions are converted back to atmospheric nitrogen gas.

(a) (i) Identify the processes P, Q, and S. [3]
(a) (ii) State the group of organisms responsible for carrying out process Q. [1]

(b) Explain how the conditions in waterlogged soils affect process S, and explain the consequences of this on plant growth. [4]

(c) Describe how nitrogen from plant proteins is recycled back into ammonium ions in the soil when a plant dies. [5]

A student investigated the effect of temperature on the rate of lipase activity. Lipase breaks down fats in milk into fatty acids and glycerol. Phenolphthalein indicator was added to a mixture of milk and sodium carbonate, turning the solution pink (alkaline pH). As fatty acids are produced, the pH decreases, and the mixture turns from pink to colorless.

Six test-tubes were set up with equal volumes of milk, sodium carbonate solution, and phenolphthalein. Lipase solution was heated separately to the required temperatures before being mixed with the milk solutions. The time taken for the pink color to completely disappear was recorded.

The results are shown in Table 1.1.

**Table 1.1**
| Temperature / °C | Time taken for pink color to disappear / seconds |
| :--- | :--- |
| 10 | 480 |
| 20 | 240 |
| 30 | 120 |
| 40 | 60 |
| 50 | 180 |
| 60 | No change after 600 |

(a) (i) State the independent variable and the dependent variable in this investigation. [2]

(ii) Identify two variables that should be controlled in this investigation. [2]

(b) (i) Describe how the student could maintain the test-tubes at the required temperatures of 10°C, 30°C, and 50°C during the experiment. [1.3]

(ii) Suggest why the student kept the lipase solution and the milk solution in the water baths for 5 minutes *before* mixing them. [1]

(c) (i) Plot a line graph of the data in Table 1.1 on the grid. (Note: For the 60°C data point, assume no reaction occurred and do not plot it or plot it as a point above 600 s). [4]

(ii) Use your graph to estimate the time taken for the pink color to disappear at 35°C. Show on your graph how you obtained your answer. [2]

(d) State the conclusion for this experiment based on the results from 10°C to 40°C. [1]

A student investigated the effect of different concentrations of sodium chloride (salt) solution on the mass of sweet potato cylinders.

Five sweet potato cylinders of identical length were cut using a cork borer. The initial mass of each cylinder was recorded. Each cylinder was then placed into a test-tube containing a different concentration of sodium chloride solution. After 45 minutes, the cylinders were removed, gently dried, and weighed again.

The results are shown in Table 2.1.

**Table 2.1**
| Concentration of sodium chloride solution / % | Initial mass / g | Final mass / g | Change in mass / g | Percentage change in mass / % |
| :--- | :--- | :--- | :--- | :--- |
| 0.0 | 3.50 | 3.85 | +0.35 | +10.0 |
| 1.0 | 3.48 | 3.48 | 0.00 | 0.0 |
| 2.0 | 3.52 | 3.31 | -0.21 | -6.0 |
| 3.0 | 3.51 | 3.12 | -0.39 | **[Calculation 1]** |
| 4.0 | 3.49 | 2.97 | -0.52 | **[Calculation 2]** |

(a) (i) Calculate the missing percentage change in mass for the 3.0% and 4.0% sodium chloride solutions. Show your working and write your answers to one decimal place. [2]

(ii) Explain why calculating the percentage change in mass is more useful than just comparing the change in mass in grams. [1.3]

(b) Describe the trend shown by the sweet potato cylinders in the different concentrations of sodium chloride solution. [2]

(c) (i) Identify one potential source of error in the step where the cylinders are dried, and suggest an improvement to reduce this error. [2]

(ii) State two safety precautions the student should take when cutting the sweet potato cylinders. [2]

(d) Suggest why using 5 sweet potato cylinders in each solution instead of 1 would improve the reliability of the results. [1]

(e) Use the results in Table 2.1 to estimate the concentration of sodium chloride inside the sweet potato cells. Explain your reasoning. [3]

A student investigated the antibacterial properties of garlic extract using the agar well diffusion method.

An agar plate was inoculated with a non-pathogenic bacterium. Five wells of equal diameter were cut into the agar. Different concentrations of garlic extract were placed into wells 1 to 5. After incubation, the diameter of the zone of inhibition (clear zone where bacteria did not grow) was measured around each well.

The experiment was repeated three times, and the results are shown in Table 3.1.

**Table 3.1**
| Concentration of garlic extract / % | Zone of inhibition diameter / mm | | | Mean diameter / mm |
| :--- | :--- | :--- | :--- | :--- |
| | Trial 1 | Trial 2 | Trial 3 | |
| 10 | 12 | 11 | 13 | 12.0 |
| 20 | 15 | 14 | 16 | 15.0 |
| 40 | 18 | 19 | 17 | **[Calculation 1]** |
| 60 | 22 | 21 | 23 | 22.0 |
| 80 | 25 | 24 | 26 | 25.0 |

(a) Calculate the missing mean diameter for the 40% concentration of garlic extract. [1]

(b) Plot a bar chart on the grid to show the mean diameter of the zone of inhibition for each concentration of garlic extract. [4]

(c) State one reason why the agar plates were incubated at 25°C rather than at human body temperature (37°C). [1.3]

(d) Explain why the student should include a control well containing only sterile distilled water, and what result they would expect to observe in this well. [2]

(e) Ginger is also thought to have antibacterial properties. Plan an investigation to determine whether ginger extract has a greater antibacterial effect than garlic extract. [5]