May/June 2025

The diagram illustrates a plant cell. What function does this cell perform?

Specialised cells, tissues and organs

What characteristics do enzymes have?

Enzyme action

The diagram depicts a transverse section of a leaf. In which areas of the leaf can photosynthesis occur?

Leaf structure

Which photomicrograph of a transverse section shows where the xylem and phloem are located in a non-woody dicotyledonous stem?

Specialised cells, tissues and organs

Learners assembled the apparatus to determine how much water a leafy shoot takes up. At the beginning, they noted the position of the air bubble. They left the apparatus for $10$ minutes, recording the distance the air bubble moved at one-minute intervals. After that, they turned on a fan directed at the leafy shoot and, for a further $10$ minutes, recorded the distance the air bubble moved from the start at each minute. Which graph should they plot using their results?

Transpiration and translocation

The proportions of each gas in inspired air and expired air are measured while a student is at rest and while the student is exercising. The findings are shown. Using the data, which statement is not correct?

Human gas exchange

Which balanced chemical equation represents aerobic respiration?

Aerobic respiration

Blood consists of several different components. The pie chart shows the percentage volume of each blood component. What percentage of the blood volume is for the component whose role is to transport oxygen?

Blood

During two full circuits of the human body, what total number of atria and ventricles does the blood pass through?

Heart

The table gives the spread of percentages for different kinds of tissue found in the walls of the aorta of people of different ages. Collagen tissue is found in the walls of blood vessels because it provides strength and support. Which conclusion about the range of percentages is correct?

Blood vessels

The table gives details about three different blood vessels, P, Q and R. One vessel is an artery, one is a capillary and one is a vein. From the table information, what is the cross-sectional area of the lumen of the vein? (Assume $\pi = 3.14$)

Blood vessels

The diagram depicts a structure that was seen through a microscope. What structure is shown in the diagram?

Cell structure and function

The table gives the estimated number of deaths in England each year from 2009 to 2019 that were caused by smoking. Using the information in the table, which statement is correct?

Disease

What is a technique used to control the malarial vector?

Disease

Which disease may be treated with antibiotics?

Antibiotics

Which structure shown is the ureter?

Urinary system

Filtration and reabsorption are processes that occur in the kidneys. The table shows the daily quantities of some substances that enter the kidneys in the blood, and the quantities of these same substances that leave the kidneys in the urine. What percentage of each substance is reabsorbed by the kidneys in one day?

Urinary system

In which part of the eye are the receptors for the pupil reflex located?

Mammalian sense organs

The body temperature inside some animals, including humans, stays unchanged even if the temperature outside varies. The graph illustrates the effect of a change in external temperature on the oxygen used by one of these animals. Which conclusion can be drawn from this graph?

Temperature control

Which of the following statements about synapses are correct?

Mammalian nervous system

Which process does not form part of a homeostatic mechanism in mammals?

Homeostasis

A nurse carries out a test on a urine sample from a patient using Benedict’s reagent. The result is positive. What could explain this outcome?

Blood glucose control

The diagram illustrates the structures present in cell X. What type of cell is X?

Cell structure and function

What causes plant shoots to grow towards light?

Coordination and response in plants

Which of the following statements about nuclear division is correct?

Nuclear division

Stem cells occur in human embryos. Which of the following statements about stem cells are correct?

Specialised cells, tissues and organs

In the placenta, which substance moves from the embryo’s blood into the mother’s blood down a concentration gradient?

Sexual reproduction in humans

What is the principal role of the prostate gland?

Sexual reproduction in humans

The graph illustrates how the levels of four hormones change during the menstrual cycle. Which line shows progesterone?

Sexual reproduction in humans

Which row identifies the factors responsible for continuous and discontinuous variation?

Variation

Which row shows the changes that happen in the eye when it focuses on a close object?

Mammalian sense organs

What is the main source of energy in most biological systems?

Energy flow

Untreated sewage has nitrates and phosphates in it. What happens in the lake if untreated sewage is discharged into it?

Effects of humans on ecosystems

What is one example of an organ?

Specialised cells, tissues and organs

DDT is an insecticide and it is damaging to living organisms. Because it is not excreted, it accumulates inside the cells of living organisms. The diagram illustrates the route followed by DDT as it enters a lake. Dissolved in water 3 taken up by aquatic plants 3 eaten by herbivorous fish 3 eaten by carnivorous fish 3 eaten by fish-eating birds Which organisms would be harmed most by the DDT?

Effects of humans on ecosystems

A newly found small vertebrate with lungs is classified as a reptile. In the key, which vertebrate is a reptile?

Concept and use of a classification system

Molecules and ions may be transported into cells and out of cells by active transport. Which statement about active transport is incorrect?

Active transport

Frogs are amphibians, so their skin is partially permeable. They live in and close to water, for example lakes and marshes, where the water has a low concentration of mineral ions. Any water they require is taken in through their skin. Biologists worry that frogs living near coastlines could become endangered if global warming causes sea level to rise. Sea water has a high concentration of mineral ions. What would happen to the frogs if their habitat were flooded with sea water?

Diffusion and osmosis

The diagram illustrates an enzyme molecule. Which diagram depicts the substrate molecule for this enzyme?

Enzyme action

The enzyme amylase speeds up the decomposition of starch into maltose. The influence of different pHs on the time needed for this decomposition to happen, while all other variables were kept constant, was investigated. Which graph shows the results of this investigation?

Effects of temperature and pH

A student looks at a human egg cell using a light microscope. The cell has a diameter of $0.12\ \text{mm}$. The student then produces a diagram of the egg cell, and the diagram’s diameter is $4.2\ \text{cm}$. What is the magnification of the drawing to the nearest whole number?

Cell structure and function

What balanced chemical equation represents photosynthesis?

Photosynthesis

Glucose formed during photosynthesis may be changed into other carbohydrates, or it may be used straight away as glucose. What is one immediate use of glucose in plants?

Photosynthesis

Which enzyme catalyses the breakdown of its substrate most efficiently at a low pH?

Effects of temperature and pH

The diagram illustrates the human digestive system. Which row correctly gives the functions of the parts labelled in the diagram?

Human digestive system

Which substances take part in the emulsification and digestion of vegetable oil in the digestive system?

Human digestive system

Which process is not an example of assimilation of absorbed food molecules?

Absorption and assimilation

What feature is characteristic of anaerobic respiration in humans?

Anaerobic respiration

Yeast is able to respire either aerobically or anaerobically. A student carries out an investigation into the rate of aerobic respiration in yeast. The temperature is kept at $35\,^{\circ}\text{C}$ while the oxygen concentration is changed. Which graph should the student obtain from the results?

Aerobic respiration

Mammals possess a double circulatory system. What does the term double circulatory system mean?

Circulatory system

Pulmonary stenosis is a condition that results from narrowing at the opening of the blood vessel carrying blood away from the right ventricle. In which part of the body will blood flow decrease first because of pulmonary stenosis?

Heart

Which row correctly names a cell, a tissue, an organ and an organ system?

Specialised cells, tissues and organs

During a single heartbeat, the muscles in the atria and ventricles tighten and then relax, driving blood out of the heart and into the circulatory system. The diagram indicates the time taken for the heart to beat twice. What is the heartbeat rate?

Heart

The photomicrograph displays a blood sample observed with a light microscope. Which row indicates the functions of the labelled parts of the blood?

Blood

Which row identifies the kind of pathogen responsible for malaria and how it is transmitted?

Disease

A bacterium infects the small intestine and releases a toxin. This toxin draws water out of the cells into the small intestine by osmosis, leading to diarrhoea and severe dehydration. Which disease is described?

Disease

Which of the following statements about immunity are correct?

Immunity

Which letter indicates the location where urea is produced?

Excretion

Which substance would not be found in the urine of a healthy person with a normal diet?

Urinary system

Which region of the eye has the highest concentration of light receptors?

Mammalian sense organs

The diagrams display the front part of an eye viewed in cross-section from above. Which diagram indicates the eye looking at a distant object in dim light?

Mammalian sense organs

Various investigations have found that the transmission of electrical nerve impulses along neurones becomes slower as age increases. Studies A, B, C and D have reported different outcomes. The average speed of a nerve impulse in people who are 40 years old is $55\,\text{m s}^{-1}$. Which study showed the smallest decrease in transmission speed between the ages of 40 and 60?

Mammalian nervous system

The diagram shows one species of arthropod. To which arthropod group does this species belong?

Concept and use of a classification system

The graph illustrates the concentration of glycogen stored in the liver of a human. In which time period is adrenaline secretion causing the blood glucose concentration to return towards its set point?

Blood glucose control

The diagram displays one of the endocrine glands in the human body, labelled X. Which hormone does endocrine gland X produce?

Mammalian hormones

A muscle cell from a horse has 64 chromosomes. How many chromosomes are present in a horse sperm cell?

Nuclear division

The diagrams illustrate the fruits of some plants. Which fruit disperses its seeds by wind?

Sexual reproduction in plants

Sperm cells are kept in a laboratory until they are ready for use in artificial insemination. The substances used to preserve the sperm cells have been found to harm the acrosomes. This causes fertility to decrease. Which statement explains why fertility may decrease?

Sexual reproduction in humans

The hormones regulating the menstrual cycle are secreted in different amounts at different times in the cycle. In pregnancy, menstruation does not occur and no eggs are produced or released. What would be the levels of hormones FSH, LH and progesterone during pregnancy?

Sexual reproduction in humans

Sickle cell anaemia results from a recessive allele. A couple have had two children. Sickle cell anaemia affects one of the children. Neither parent nor the other child has sickle cell anaemia. The couple are expecting a third child. What is the probability that this third child will be male with sickle cell anaemia?

Inheritance

Every human gamete contains a single sex chromosome. Which statement is the correct one?

Sexual reproduction in humans

What does the term food chain mean?

Energy flow

Soil with a higher water content provides favourable conditions for denitrifying bacteria to multiply. Which effects will be observed on the growth of plants in this soil?

Nutrient cycles

Which combination of factors will cause diffusion to occur at the greatest rate through a membrane?

Diffusion and osmosis

These statements outline the process of eutrophication, which can occur when excess nitrogen fertiliser washes from fields into streams. They are not arranged in the right sequence. 1. Bacteria decay dead plants and use up oxygen. 2. Animals die or leave the area. 3. Light cannot reach aquatic plants. 4. The growth rate of algae increases. 5. Aquatic plants die. In which order should these statements be arranged?

Effects of humans on ecosystems

A leaf from pondweed ($Elodea$) is mounted on a microscope slide. Sodium chloride solution is then added as a drop. The leaf cells are observed using a light microscope. Which statement describes the cells seen through the microscope?

Diffusion and osmosis

Give one example of a biological catalyst.

Enzyme action

What outcome would occur if an enzyme's active site were damaged?

Enzyme action

The graph illustrates the activity rate of enzyme X at a range of pH values. All other conditions are held constant. Using the data presented in the graph, which statement is correct?

Effects of temperature and pH

Students carried out an investigation into the rate of photosynthesis at different light intensities. They measured how many oxygen bubbles a submerged aquatic plant gave off per minute when it was positioned at various distances from a light source. Which results would be expected from this investigation?

Photosynthesis

Larger molecules in cells are formed from smaller molecules.

Biological molecules

Fig. 2.1 displays a pond food web.

Energy flow

Fig. 3.1 illustrates the human digestive system. Fig. 3.2 illustrates a cross-section through organ E in a healthy person and in a person with coeliac disease.

Human digestive system

Pathogens are responsible for transmissible diseases.

Immunity

Carbon dioxide pollution in the air is helping to drive global warming.

Photosynthesis

Sycamore trees ($Acer\ pseudoplatanus$) occur across much of Europe.

Sexual reproduction in plants

In humans, ABO blood group inheritance is a case of codominance.

Inheritance

Pectinase is an enzyme made by fungi. In industrial production on a large scale, pectinase is produced by growing fungi in fermenters.

Biotechnology

A pea seed is placed in a pot of soil and kept under the ideal conditions needed for germination. The pot is then left in a dark room for 10 days. Fig. 1.1 shows how the germinating seed appears on different days.

Sexual reproduction in plants

Scientists have considered how to nourish the world’s human population in a healthy and sustainable manner. They have developed a model known as the planetary health plate. It is displayed in Fig. 2.1.

Diet

Staphylococcus aureus is a pathogen that infects humans. Antibodies and antibiotics can destroy it. Its cells are spherical and about $1\,\mu\text{m}$ in diameter. Fig. 3.1 shows an S. aureus cell.

Antibiotics

Fig. 4.1 illustrates a human bronchiole together with some specialised cells from the inner lining that encircles the lumen.

Human gas exchange

Rhizomucor pusillus is a fungus that occurs in heaps of dead plant vegetation. Its optimum growth rate lies between $60\,^{\circ}\text{C}$ and $70\,^{\circ}\text{C}$.

Concept and use of a classification system

A cell nucleus contains DNA molecules, and these molecules control cell function. Fig. 6.1 shows a diagram of one of these DNA molecules.

DNA

Photosynthesis and transpiration are two processes carried out in a plant leaf.

Leaf structure

A student examined how gravity affected germinating seeds. Eight pea seeds were used.\n\nAs germination began, the pea seeds first formed radicles (roots). The radicle length can be measured between the dotted lines, as shown in Fig. 1.1.\n\nThe student fixed four of the seeds with germinating radicles to the cork base on each of two electric motors, as shown in Fig. 1.2. The cork was kept wet throughout the investigation and the apparatus was kept in the dark.\n\nThe student then switched on motor A so that the cork base turned very slowly for two days, in the direction shown by the arrow.\n\nMotor B was left switched off, so the cork base did not turn.\n\nFig. 1.3 shows the pea radicles after 2 days.\n\nAnother student investigated the growth of the shoots (plumules) of germinating pea seeds for eight days. The student’s results are shown in Table 1.1.

Coordination and response in plants

Fig. 2.1 illustrates a section of the shoot from a pea seedling.

Photosynthesis

Urine tests may be used to diagnose diseases. Indicator paper strips are placed into a urine sample. They detect substances in the sample that are excreted in urine but are not usually found in the urine of a healthy person. Three examples of indicator paper strips are: • Diastix® to detect glucose • Albustix® to detect protein • Ketostix® to detect ketones. People with diabetes excrete glucose and ketones. People with nephritis excrete protein. People with malnutrition excrete ketones. Table 3.1 gives the results of tests on the urine samples of four individuals (D, E, F and G). A tick (✓) shows a positive result and a cross (✗) shows a negative result.

Excretion

Catalase is an enzyme present in living cells. It speeds up the decomposition of hydrogen peroxide into oxygen and water. Some plant cells are a source of catalase. If plant material is crushed and mixed with water, a suspension containing the cell contents of the plant can be made. When hydrogen peroxide solution is added to this suspension, the oxygen released appears as gas bubbles. These bubbles gather to make a foam layer at the top of the suspension. The height of any foam formed can be measured. A greater height shows greater catalase activity. A student compared catalase activity in the cells of three plant species by measuring the foam height produced in each. Three cell suspensions, one each of celery, apple and potato, were supplied in separate beakers. The student used these steps: • stir the celery cell suspension in the beaker with a clean stirring rod • use a syringe to place $2\ \text{cm}^3$ of celery cell suspension into a clean test-tube • add $2\ \text{cm}^3$ of hydrogen peroxide solution to this test-tube using a clean syringe • begin timing at once • after $60$ seconds, measure the height of any foam formed and write down the result. Carry out the same steps with the apple cell suspension and then with the potato cell suspension. Fig. 1.1 shows the combined contents of each of the three test-tubes after $60$ seconds.

Enzyme action

Fig. 2.1 shows a photomicrograph of a celery plant section.

Specialised cells, tissues and organs

Fig. 3.1 illustrates mustard plant seedlings placed in Petri dishes on moist filter paper.

Photosynthesis