Biology 9700 · AS & A Level
Oct/Nov 2025
120 questions from this paper, with worked solutions and instant marking.
On a photomicrograph at a magnification of \times5000, a chloroplast has a diameter of 25 mm. What is the chloroplast's actual diameter?
The microscope in cell studies
Which molecules have at least four double bonds?
Carbohydrates and lipids
In some individuals, a mutation may change the beta chains in their haemoglobin molecules. Consequently, polar amino acids on the outer surfaces of the chains are replaced by non-polar amino acids. What effect will this have on haemoglobin?
Proteins
The graph illustrates how substrate concentration affects an enzyme-catalysed reaction both in the presence and in the absence of a competitive inhibitor. What is the effect of the competitive inhibitor on $V_{\max}$ and $K_m$?
Factors that affect enzyme action
This graph displays how energy changes in a chemical reaction. What activation energy is shown when an enzyme has been added?
Mode of action of enzymes
The diagram shows an enzyme, its substrate and an enzyme-substrate complex. Which statement explains why this substrate can enter the active site of this enzyme?
Mode of action of enzymes
What are the principal functions of glycolipids in cell surface membranes?
Fluid mosaic membranes
A sample of healthy plant cells collected from the same tissue is put into a beaker of distilled water. The cells alter in size. What could account for this change in size?
Movement into and out of cells
A student investigating surface area to volume ratio and diffusion prepared a cuboid, S1, from agar coloured blue with a pH indicator. The dimensions of S1 are given in the diagram. The student then prepared a second agar cuboid, S2. For S2, each dimension — the length, the width and the height — was half the corresponding dimension of S1. Each cuboid was put into a test-tube and then covered with acid. The student measured how long each cuboid took to turn completely from one colour to another. Every variable except the size of the cuboids was kept the same. Which row gives the surface area to volume ratio of S1 and the time taken for S1 to change colour completely in acid compared with the time taken for S2 to change colour completely?
Movement into and out of cells
Two test-tubes, X and Y, were prepared, each containing the same volume of solution X or solution Y, respectively. A large number of type P cells and a large number of type Q cells were placed into test-tube X and also into test-tube Y. After a few minutes, samples of the solutions were removed and the cells were viewed using a microscope. In solution X, every cell of type P had burst, whereas cell type Q had not burst. In solution Y, none of the cells had burst. Which row correctly identifies cell type Q and solutions X and Y?
Movement into and out of cells
A human muscle cell has 46 chromosomes. During the stages of the mitotic cell cycle, how many centromeres will be found in a cell?
Replication and division of nuclei and cells
What is one role of Golgi bodies?
Cells as the basic units of living organisms
Telomeres get shorter in every cell cycle of a specialised cell. In which phase of the cell cycle do telomeres become shorter?
Replication and division of nuclei and cells
The photomicrographs display stages of mitosis. Which sequence shows the stages of mitosis in the correct order?
Chromosome behaviour in mitosis
The gene responsible for coding protein R has a length of 130 kb. The mass of protein R is 220 kDa. A typical amino acid has a mass of 110 Da. (1000 base pairs = 1 kb, 1000 Da = 1 kDa) Which row is correct?
Cells as the basic units of living organisms
The diagram shows part of a DNA molecule. Two of the bases in this section are marked 1 and 2. Which row correctly names bases 1 and 2?
Cells as the basic units of living organisms
Which row identifies the roles of the enzymes DNA polymerase and DNA ligase?
Replication and division of nuclei and cells
The table lists several DNA triplet codes for certain amino acids. arginine: GCA, GCC, GCG asparagine: TTA, TTG cysteine: ACA, ACG STOP: ATC glycine: CCA, CCG, CCT lysine: TTC, TTT proline: GGA, GGC valine: CAC A section of the template DNA strand that codes for part of a polypeptide is shown below. CCA TTC ACG GCG TTA GCA During DNA replication, two mutations take place in this sequence. Which mutated DNA would produce two different amino acids?
Replication and division of nuclei and cells
The diagram depicts a vertical section of part of the stem of a dicotyledonous plant. Three kinds of structures are labelled. What are the structures U, V and W?
Cells as the basic units of living organisms
Which characteristics of xylem vessels reduce resistance to water flow? 1. Lignin makes up a secondary wall that is not continuous. 2. No cross walls separate the vessel elements. 3. The xylem vessels are narrow tubes.
Movement into and out of cells
What makes water travel from the root hair cells to the endodermis?
Movement into and out of cells
What changes take place as carbohydrate is transported into a sink?
Movement into and out of cells
In the human body, a cell is specialised for the synthesis and secretion of lipids. Which row indicates the organelles needed by the cell for lipid synthesis and secretion?
Carbohydrates and lipids
Which statement accurately compares blood plasma with tissue fluid in a healthy person?
Movement into and out of cells
The body keeps an average normal blood pH of 7.4. Which row best describes the conditions that would raise the dissociation rate of haemoglobin the most during a period of intense exercise?
Water
The graph illustrates how blood pressure changes throughout one cardiac cycle. What event is occurring at time X?
Cells as the basic units of living organisms
How many times does a carbon dioxide molecule have to cross a cell surface membrane to move from the tissue fluid into the blood plasma? (Assume that there are no pores between the cells through which the carbon dioxide molecule has to pass.)
Movement into and out of cells
In a healthy human, two epithelial cell types, 1 and 2, are found in the mammalian gas exchange system. Which row indicates the function and distribution of these epithelial cell types?
Cells as the basic units of living organisms
Which tissues would be visible in a photomicrograph of the tracheal wall?
Cells as the basic units of living organisms
The graph illustrates the reduction in cases of tuberculosis (TB) in a country from 1910 to 2000. Which factors may have helped bring about the fall during this period?
Cells as the basic units of living organisms
The pathogens responsible for certain diseases are spread by vectors. Which disease is spread by a vector that can be controlled by eliminating standing pools of water?
Cells as the basic units of living organisms
In what way does penicillin affect bacteria?
Mode of action of enzymes
The hybridoma method is used to make monoclonal antibodies. Which two cell types are combined in this method?
Cells as the basic units of living organisms
The photomicrograph displays part of a cell. Which row is correct?
The microscope in cell studies
What name is given to a non-specific immune response?
Replication and division of nuclei and cells
Which of the following statements about viruses is correct?
Cells as the basic units of living organisms
Solution X was examined for non-reducing sugars. It contained no reducing sugars. The steps below may be used when testing for the presence of biological molecules. 1. Benedict’s solution is added to the test-tube. 2. Dilute hydrochloric acid is added to the test-tube. 3. Sodium hydrogencarbonate is added to the test-tube. 4. The test-tube is heated in a water-bath. Which sequence of steps is correct for identifying non-reducing sugars in solution X?
Testing for biological molecules
The diagram illustrates the structure of part of a biological molecule. Which of the following statements about this biological molecule are correct?
Proteins
Which diagram shows a covalent bond linking monomers to make a biological polymer in eukaryotes?
Proteins
Which characteristic of storage polysaccharides means that they do not affect the water potential of cells?
Carbohydrates and lipids
A student viewed some cells with a microscope fitted with an eyepiece graticule. They then took out the slide containing the cells and substituted a stage micrometer with a millimetre scale, then aligned the eyepiece graticule as illustrated. What is the greatest diameter of the cell labelled X?
The microscope in cell studies
Which bonds linking amino acids maintain the form of the secondary structure and also the tertiary structure of proteins?
Proteins
Resilin is a protein present in insect wings. It is an elastic, fibrous protein, and scientists have proposed that it may play an important part in enabling an insect’s wings to fold and unfold without damage. Peptidyl transferase is an enzyme that catalyses the condensation of amino acids during translation to produce resilin. Which statements are correct?
Proteins
Collagen is a protein that contributes to strengthening the skin and improving its elasticity and hydration. As aging occurs, the body produces less collagen, which can result in dry skin and the development of wrinkles. Which row gives the correct description of the structure of collagen in the skin?
Proteins
What effect does an enzyme have in an enzyme-catalysed reaction?
Mode of action of enzymes
In what way is the Michaelis-Menten constant ($K_m$) applied?
Mode of action of enzymes
A group of students studied how pH affected the speed of starch digestion by amylase at $20\,^{\circ}\mathrm{C}$. Into a test-tube, they placed $2\,\mathrm{cm}^3$ of a 1% amylase solution together with $1\,\mathrm{cm}^3$ of pH 4 buffer. They then added $2\,\mathrm{cm}^3$ of a starch solution, which contained $0.02\,\mathrm{g}$ of starch, to the test-tube. The time for the starch to be digested (to disappear) was recorded. These steps were then carried out again using pH 5, pH 6, pH 7 and pH 8 buffers. The results are shown in the table: pH 4 → 4.0 min, pH 5 → 1.5 min, pH 6 → 1.0 min, pH 7 → 2.5 min, pH 8 → 6.0 min. Which graph matches these data?
Factors that affect enzyme action
Which of the following statements about a non-competitive inhibitor of enzyme action are correct?
Mode of action of enzymes
What factor can raise the fluidity of the cell surface membrane at low temperatures?
Fluid mosaic membranes
Which of the following statements about proteins and glycoproteins in cell surface membranes are correct?
Fluid mosaic membranes
In an experiment, four cubes of colourless agar, each a different size, were put into a blue dye. The time for each cube to become blue was measured. Which row gives the surface area and volume of the cube that took the greatest time to become fully blue?
Movement into and out of cells
Which structures are found in a cell that causes cholera?
Cells as the basic units of living organisms
The stalk of a dandelion flower is a hollow tube known as a scape. Sections of the scape are cut along the dotted lines shown and then placed in sucrose solutions with different water potentials. Which diagram indicates the piece that is placed in the sucrose solution with the highest water potential?
Movement into and out of cells
Telomeres stop genes from being lost when DNA replicates. Which row correctly identifies the cell types that have telomeres?
Replication and division of nuclei and cells
Which of these listed events occur during mitosis? 1. interphase 2. prophase 3. cytokinesis
Chromosome behaviour in mitosis
The photomicrograph displays 17 cells in different stages of the mitotic cell cycle. Which row matches this photomicrograph?
Chromosome behaviour in mitosis
The flow diagram illustrates several stages involved in the replication of a lagging strand of DNA. At which stage of DNA replication is the enzyme DNA ligase used?
Replication and division of nuclei and cells
Within a gene, each of the 20 common amino acids is specified by three bases in neighbouring nucleotides. Why does the number of amino acids differ from the number of possible triplet codes?
Proteins
In what way is a primary transcript altered to produce mRNA?
Cells as the basic units of living organisms
The diagram illustrates protein synthesis in a prokaryote. Which row correctly identifies molecule X, structure Y and the anticodon of tRNA 1?
Replication and division of nuclei and cells
The photomicrographs display sections through two plant organs. Which letter labels a cell that is found together with companion cells in a tissue in a root?
Cells as the basic units of living organisms
Which row gives the correct description of the pressure in the xylem and the water potential in the root hair cells involved in water transport in a transpiring plant?
Movement into and out of cells
Which organelles contain a partially permeable membrane?
Fluid mosaic membranes
Which row correctly matches the definitions of each of the key terms used in transpiration?
Movement into and out of cells
Which set of features is typical of a phloem sieve tube element immediately after it has been loaded from a source?
Cells as the basic units of living organisms
Which blood vessel transports blood at the lowest pressure?
Movement into and out of cells
The photomicrograph displays cells present in mammalian blood. What is cell P called?
Cells as the basic units of living organisms
The diagram illustrates the Bohr shift in actively respiring cells. What is responsible for the shift from L to M?
Movement into and out of cells
The bar chart illustrates the average thickness of the walls of the main chambers in a mammalian heart. Which row correctly identifies the heart chambers?
Cells as the basic units of living organisms
The diagram illustrates sections of the human gas exchange system together with the cells or structures linked to them. Parts: alveolus, bronchiole, bronchus, trachea. Cells or structures: ciliated cells, squamous epithelial cells, C-shaped rings of cartilage, ciliated cells and goblet cells. Which diagram shows the connections that correctly pair the parts with their cells or structures?
Cells as the basic units of living organisms
The photomicrograph shows the wall of a bronchus viewed using a light microscope. Which row correctly names the structures labelled?
The microscope in cell studies
What factors influence the global distribution pattern of malaria?
Replication and division of nuclei and cells
Which molecule might be a self antigen?
Cells as the basic units of living organisms
Mouse cells were cultured in a dish that contained a growth medium. Radioactively labelled amino acids were added to the growth medium. The table displays how long it took for the radioactively labelled amino acids to appear in three different organelles, R, S and T. Which row correctly names the organelles?
Cells as the basic units of living organisms
The diagram illustrates an antibody molecule with several parts labelled. Which row correctly identifies the parts that make up an antigen-binding site and possess identical amino acid sequences?
Proteins
An electron micrograph shows a slice through a cell. What would be found in this kind of cell?
The microscope in cell studies
A student performed four tests for biological molecules. The results are listed in the table: iodine: orange; biuret: purple; Benedict’s: orange; emulsion: clear. The diagrams illustrate molecules or sections of molecules. Which pair is present in the solution?
Testing for biological molecules
The diagram illustrates some links between carbohydrate features. Which row gives the correct match between a carbohydrate and some of its features?
Carbohydrates and lipids
The diagram illustrates a triglyceride molecule. Which statement correctly describes the structure and function of this triglyceride?
Carbohydrates and lipids
Enzyme P has been discovered in a tropical grass. This enzyme speeds up the hydrolysis of the fungal polysaccharide chitin into amino sugars. It also stops the action of an enzyme in locust guts that speeds up the digestion of amylose. Which row gives a description of the functions of enzyme P?
Mode of action of enzymes
The diagram illustrates a stage micrometer, whose divisions are 0.1 mm apart, seen through an eyepiece fitted with a graticule. That same eyepiece is then used to view a blood smear. How many graticule divisions would span the diameter of a lymphocyte measuring 10 µm?
The microscope in cell studies
Which statement gives the correct explanation of the outcome when the two molecules shown in the diagram react with each other?
Testing for biological molecules
Which row gives the description of amylopectin?
Carbohydrates and lipids
What is one characteristic of triglyceride molecules?
Carbohydrates and lipids
An unsaturated fatty acid molecule has a tail attached to its carboxyl group that contains 17 carbon atoms. The tail has three double bonds. How many hydrogen atoms are present in the tail?
Carbohydrates and lipids
Which statement regarding phospholipids in the bilayer of a cell surface membrane is correct?
Fluid mosaic membranes
Which statements about enzymes that follow the lock-and-key hypothesis are correct?
Mode of action of enzymes
The graph presents the findings from an investigation into how amylase affects starch at three different temperatures. Which statements give the correct conclusions from these results?
Factors that affect enzyme action
The rate of enzyme-catalysed reactions in human cells is controlled. What could be involved in this regulation?
Factors that affect enzyme action
Proteins in the cell surface membranes of human cells and mouse cells were tagged using fluorescent dyes. The human cells received a red dye, whereas the mouse cells received a green dye. A human cell and a mouse cell were then joined to produce a hybrid cell. Initially, the two dyes stayed separate. After 40 minutes, both dyes were distributed uniformly throughout the hybrid cell surface membrane. What accounts for this observation?
Fluid mosaic membranes
Which of the following statements about the cell surface membrane are correct?
Fluid mosaic membranes
Cell structures may be separated by centrifuging the cells in a sucrose density gradient. In this process, the cells are broken open and the cell structures are divided into fractions. The diagram shows where some of these fractions are found in a sucrose density gradient. Fraction 1: ribosomes; fraction 2: lysosomes; fraction 3: mitochondria; fraction 4: chloroplast. Which fractions contain cell structures that carry out protein synthesis?
Cells as the basic units of living organisms
The diagram depicts two agar cylinders. Both cylinders are put into a dye solution at the same time. The time needed for the dye to diffuse to the centre of each cylinder is measured. Which statement explains why the dye reaches the centre of one agar cylinder more quickly than the other agar cylinder?
Movement into and out of cells
What functions do adult stem cells have in humans? 1 repair other cells through mitosis 2 divide to replace cells in tissues 3 differentiate to form a new organism
Replication and division of nuclei and cells
Which of the following statements about the mitotic cell cycle are correct? 1 DNA is copied semi-conservatively during mitosis. 2 DNA is never altered from one generation of cells to the next generation. 3 The daughter cells at the end of a mitotic cell division have the capacity to make the same enzymes as the parent cell. 4 The same amount of DNA is passed to the nuclei of two new cells at the end of a mitotic cell division.
Replication and division of nuclei and cells
The photomicrograph depicts a stage in the cell cycle. Which stage is visible in the photomicrograph?
Replication and division of nuclei and cells
The diagram shows an ATP molecule. Identify the components of ATP labelled J, K and L.
Carbohydrates and lipids
Which of the following statements about complementary base pairing are correct? 1 It takes place in translation. 2 Purines and pyrimidines are equal in size. 3 The two paired bases are the same length. 4 Uracil makes three hydrogen bonds with adenine.
Replication and division of nuclei and cells
Which statement is true about protein synthesis?
Proteins
A mutation took place in this starting DNA nucleotide sequence. $CTAGAATCCTCTCCC$ Once the mutation had occurred, the altered DNA nucleotide sequence coded for the amino acids Asp, Leu, Gly and Glu. The table gives the amino acids coded for by each DNA triplet. Which type of gene mutation took place in the DNA nucleotide sequence?
Replication and division of nuclei and cells
The photomicrograph displays a longitudinal section of part of a plant stem. Which row correctly names structures P, Q and R?
The microscope in cell studies
Which statement about the route followed by a water molecule as it moves from the soil into the xylem is correct?
Movement into and out of cells
The diagram displays a plant cell. Which labelled organelles are expected to contain nucleotides?
Cells as the basic units of living organisms
Amino acids are transferred from a phloem sieve tube element into a root cell. During this transfer at the sink, how do the water potential and the volume of liquid in the phloem sieve tube element change?
Movement into and out of cells
The table compares blood pressure in three major blood vessels during diastole. Which row correctly names the three blood vessels?
Cells as the basic units of living organisms
Red blood cells can contain a molecule called 2,3-bisphosphoglycerate (2,3-BPG). If 2,3-BPG binds to haemoglobin, a greater partial pressure of oxygen is required for haemoglobin to become 50% saturated with oxygen. Which of the following statements about the effect of 2,3-BPG are correct?
Proteins
An individual has a small opening in the septum between the ventricles. This condition is known as a ventricular septal defect (VSD). Apart from this, the person has no other heart defects. During ventricular systole, what is the direction of the net flow of blood in this person’s heart?
Movement into and out of cells
The diagram shows a transverse section of a human bronchus. Which labelled tissue is cartilage?
Cells as the basic units of living organisms
What keeps the concentration gradient between the blood and the air in the alveolus from disappearing?
Movement into and out of cells
Which row correctly names the pathogens that cause malaria and TB?
Cells as the basic units of living organisms
What measure could be used to reduce the risk of a cholera outbreak in a town?
Movement into and out of cells
The graph presents the percentage of tuberculosis (TB) patients who were also recorded as having HIV, from 2004 to 2011. Which statement about the graph is correct?
Cells as the basic units of living organisms
Four different treatments were trialled in a human volunteer over the course of a year. One of the treatments was a vaccine. The treatments were injected into the volunteer, and blood samples were collected after two weeks. These samples were then analysed to find the cell count for four types of cell. The results are shown in the table. (Assume that the volunteer's baseline blood cell count was the same before each treatment.) Which treatment was the vaccine?
Cells as the basic units of living organisms
The picture shown here has been created with a microscope. How many of the following statements about this image are correct? • It is an electron micrograph. • It shows part of a eukaryotic cell. • It shows at least one mitochondrion. • It shows a specimen viewed at more than ×400 magnification.
The microscope in cell studies
A bacterial pathogen makes a protein that functions as a toxin. This toxin is harmful to humans. People may be vaccinated so they are protected from the effects of this pathogen. Which statement describes the sequence of events that takes place in a vaccinated person to protect them from the effects of this pathogen?
Proteins
Bacterial ribosomes are composed of two subunits, and each ribosome contains a total of three rRNA molecules. An investigation of all the 70S ribosomes in one cell of the bacterium Escherichia coli found that there were: • 57 a0000 rRNA molecules • three kinds of rRNA molecule • 19 a0000 copies of each kind of rRNA molecule. What number of 70S ribosomes were present in the E. coli cell?
Cells as the basic units of living organisms
Radioactively labelled amino acids are placed into a tracheal cell, which uses them to synthesise mucus (a glycoprotein). What pathway will the amino acids follow?
Proteins
Which of the features labelled in the diagram may be found in viruses? The diagram identifies: 1 DNA, 2 protein coat, 3 70S ribosomes, 4 RNA.
Cells as the basic units of living organisms
The diagram illustrates some stages in a laboratory procedure used to detect whether non-reducing sugars are present in a food sample. Several terms are omitted. Step X Step Y end colour Z. Which terms are correct for the expected result when the concentration of non-reducing sugar is very low?
Testing for biological molecules
A number of biological molecules are polymers built from repeating monomer units. Which row correctly names the monomer for each biological molecule?
Testing for biological molecules