IGCSE Biology 0610/42 May/June 2025 Past Paper with Answers

Question 1

In the human gas exchange system air passes from the larynx down a single wide tube whose wall is supported by rings of cartilage. This tube divides into two tubes, one entering each lung, and inside each lung these branch into many much narrower tubes. Which option names, in order, the single wide tube, the two tubes entering the lungs, and the narrow branching tubes?

1. the single wide tube is the trachea, the two tubes entering the lungs are the bronchi, and the narrow branching tubes are the bronchioles
2. the single wide tube is the oesophagus, the two tubes entering the lungs are the bronchioles, and the narrow branching tubes are the bronchi
3. the single wide tube is a bronchus, the two tubes entering the lungs are the alveoli, and the narrow branching tubes are the bronchioles
4. the single wide tube is the trachea, the two tubes entering the lungs are the alveoli, and the narrow branching tubes are the bronchi

Question 2

The wide tube that carries air down towards the lungs has rings of cartilage in its wall. What is the function of this cartilage?

1. it holds the airway open and stops it collapsing
2. it produces mucus to trap dust and bacteria
3. it sweeps mucus upwards out of the airway
4. it carries out gas exchange with the blood

Question 3

Inspiration is the process of breathing air into the lungs. Which option correctly explains how inspiration occurs?

1. the diaphragm contracts and flattens, the external intercostal muscles contract to move the ribs up and out, the volume of the chest increases and the pressure inside falls, so air is drawn into the lungs
2. the diaphragm relaxes and domes upwards, the ribs move down and in, the chest volume decreases and the pressure rises, so air is drawn into the lungs
3. the diaphragm contracts and flattens, the ribs move down and in, the chest volume decreases, so air is forced out of the lungs
4. the diaphragm relaxes, the chest volume stays the same, and air diffuses into the lungs down a concentration gradient

Question 4 · Answer A

Step 1: Goblet cells in the lining of the airways secrete sticky mucus that traps pathogens and dust particles in the air. Step 2: Ciliated cells have tiny hair-like cilia that beat to sweep the trapped mucus up and out of the airways. Step 3: Red blood cells, palisade cells and root hair cells do not line the airways, so the other options are wrong.

Question 5 · Answer A

Step 1: Thicker, stickier mucus narrows and blocks the airways, reducing the flow of air and the surface area available for gas exchange. Step 2: Less oxygen therefore reaches the blood and the muscles, so less aerobic respiration can take place. Step 3: With less respiration, less energy is released for muscle contraction, so the person cannot exercise as well.

Question 6 · Answer A

Step 1: Each Ff parent produces gametes carrying F or f, so the cross Ff x Ff gives offspring FF, Ff, Ff and ff. Step 2: Only the ff child has two recessive alleles and therefore has cystic fibrosis, which is 1 of the 4 possible offspring. Step 3: So the probability of a child with cystic fibrosis is 1 in 4, which is 25% or 0.25.

Question 7 · Answer A

Step 1: Red blood cells contain haemoglobin and transport oxygen, while plasma is the liquid that transports dissolved substances such as nutrients and carbon dioxide. Step 2: Lymphocytes produce antibodies and phagocytes carry out phagocytosis to engulf pathogens. Step 3: Platelets help the blood to clot, so the first option matches every component to the correct function.

Question 8 · Answer A

Step 1: HIV is carried in the blood and other body fluids of an infected person. Step 2: It can pass directly from one person to another through contact with infected blood, such as a shared needle. Step 3: Influenza is spread through the air, cholera through contaminated water, and athlete’s foot by contact with surfaces, so HIV is the blood-borne pathogen.

Question 9 · Answer A

Step 1: Indirect transmission means the pathogen passes through the environment, such as food, water or objects, before reaching a new person. Step 2: Contaminated food, water and surfaces are all environmental routes, so they are indirect. Step 3: Blood contact, sexual contact, touching an infected person and passing through the placenta or breast milk are all direct routes, so only the first pair is indirect.

Question 10 · Answer A

Step 1: Each antibody has a specific shape that is complementary to the antigen on a particular pathogen. Step 2: The antibody binds to that antigen, then marks, clumps together or neutralises the pathogen or its toxins. Step 3: This makes the pathogen easier to destroy, for example by phagocytosis, so the first option is correct.

Question 11 · Answer A

Step 1: In active immunity the body is stimulated by infection or vaccination to make its own antibodies and memory cells. Step 2: The memory cells allow a fast secondary response, so active immunity is long-term. Step 3: In passive immunity ready-made antibodies are received from outside, such as in breast milk, so no memory cells are made and the protection is only short-term.

Question 12 · Answer A

Step 1: Percentage increase = (increase ÷ original value) × 100. Step 2: The increase is 325 − 80 = 245 million tonnes, so the percentage increase is (245 ÷ 80) × 100 = 306.25%. Step 3: Rounded to two significant figures this gives 310%.

Question 13 · Answer A

Step 1: Chromosomes are made of a molecule called DNA. Step 2: A gene is a length of DNA at a particular position that codes for a protein. Step 3: Starch and glycogen are storage carbohydrates and haemoglobin is a protein, so none of these carries genes.

Question 14 · Answer A

Step 1: Breeding the GM crop for several generations lets scientists check that the new gene is reliably passed on and expressed in every plant. Step 2: It also lets them confirm the plants give a good, consistent yield and quality and show no unexpected harmful effects. Step 3: Growing many generations also builds up a large stock of seed to sell to farmers, so the first option is correct.

Question 15 · Answer A

Step 1: A restriction enzyme cuts the required gene out of the donor DNA, and the same enzyme is used to cut open a bacterial plasmid so that the cut ends are complementary. Step 2: The gene is joined into the plasmid using the enzyme ligase, forming recombinant DNA. Step 3: The recombinant plasmid is put into a bacterium, which then multiplies and expresses the gene to make the protein.

Question 16 · Answer A

Step 1: Pollination is prevented if the GM pollen cannot reach the wild plants. Step 2: Growing the crops in glasshouses or removing the anthers stops the pollen from being released or carried to the wild plants. Step 3: Planting the crops close to wild plants, adding more insects, or making more pollen would all increase pollination, so the first option is correct.

Question 17 · Answer A

Step 1: GM crops can be engineered to contain extra nutrients, such as added vitamins, improving their nutritional value. Step 2: They can also be given a higher yield or a longer shelf life, which are clear advantages. Step 3: The other options describe impossible or untrue claims, so only the first pair are real advantages.

Question 18 · Answer A

Step 1: An adaptive feature is passed on from parents, so it is an inherited feature. Step 2: It is a feature that increases the chance an organism can survive in its environment. Step 3: It also helps the organism to reproduce, so the words are inherited, survive and reproduce.

Question 19 · Answer A

Step 1: A xerophyte leaf reduces water loss, so it is often rolled or curled to trap moist air. Step 2: Hairs and stomata sunk into pits on the sheltered inner surface trap water vapour and reduce evaporation, and a thick waxy cuticle cuts water loss through the surface. Step 3: Broad thin leaves with many open stomata, or floating leaves, lose water quickly and are not xerophyte features.

Question 20 · Answer A

Step 1: There are 1000 micrometres in 1 millimetre, so to change micrometres to millimetres you divide by 1000. Step 2: 1.276 ÷ 1000 = 0.001276. Step 3: So 1.276 µm is equal to 0.001276 mm.

Question 21 · Answer A

Step 1: Plant cell walls are made of the carbohydrate cellulose. Step 2: Cellulose forms strong fibres that give the cell wall its strength and support. Step 3: Glucose is a small sugar, glycogen is an animal storage carbohydrate, and protein is not a carbohydrate, so cellulose is the answer.

Question 22 · Answer A

Step 1: In a dry habitat the plant must save as much water as possible. Step 2: A swollen, fleshy stem can store water inside it for use when there is no rain. Step 3: Thin draining stems, large open pores and no outer covering would all lose water, so they are not adaptations to dryness.

Question 23 · Answer A

Step 1: The wide, shallow roots of species 1 cover a large area just below the surface, so they quickly absorb rainwater before it evaporates or drains away. Step 2: The single long, deep root of species 2 grows down to reach water held deep in the soil. Step 3: Both systems are adaptations for taking up water, so the options saying they only anchor the plant or carry out photosynthesis are wrong.

Question 24 · Answer A

Step 1: The nitrate ions are more concentrated inside the cell than in the soil, so they must move against the concentration gradient. Step 2: Moving particles against a gradient needs active transport, which uses protein carriers in the cell membrane and energy released by respiration. Step 3: Diffusion and osmosis move substances down a gradient without energy, so they cannot explain this uptake.

Question 25 · Answer A

Step 1: Nitrogen fixation turns unreactive nitrogen gas into useful nitrogen compounds. Step 2: Lightning provides enough energy to combine nitrogen with oxygen, and nitrogen-fixing bacteria convert nitrogen gas into compounds in the soil and in root nodules. Step 3: Photosynthesis, respiration, evaporation and combustion do not fix nitrogen, so the first option is correct.

Question 26 · Answer A

Step 1: The movement of water across a partially permeable membrane is called osmosis. Step 2: Water moves from the soil, where there is a higher water concentration, into the cell, where there is a lower water concentration. Step 3: Active transport moves ions using energy, respiration releases energy, and transpiration is water loss from leaves, so osmosis is correct.

Question 27 · Answer A

Step 1: Both a root hair cell and a bacterial cell have a cell wall, cell membrane, cytoplasm, ribosomes and DNA, so these are the similarities. Step 2: The root hair cell also has a nucleus, mitochondria and a large vacuole, which the bacterial cell does not have. Step 3: The bacterial cell has no nucleus and its DNA forms a loop, so the first option correctly gives the differences and similarities.

Question 28 · Answer A

Step 1: For each enzyme the area of jelly digested rises to a peak at its optimum pH and then falls, so each has an optimum. Step 2: Enzyme L peaks at pH 2 with the higher activity of about 160 mm², while enzyme M peaks at pH 10 at about 140 mm². Step 3: Enzyme M is still active across a wide range of higher pH, so it works over a wider pH range than enzyme L, making the first option correct.

Question 29 · Answer A

Step 1: Enzyme M works best in alkaline conditions, so a pH of 2 is far from its optimum. Step 2: The very acidic conditions denature the enzyme, changing the shape of its active site. Step 3: The protein substrate can no longer fit into the changed active site, so no jelly is broken down.

Question 30 · Answer A

Step 1: Enzyme L is a protease that works best at the very low pH of about 2. Step 2: The stomach is the part of the digestive system with strongly acidic conditions, and the protease that works there is pepsin. Step 3: Amylase digests starch in the mouth, lipase digests fats in the small intestine, and trypsin works in the small intestine, so pepsin in the stomach is correct.