9700 Biology November 2025 Question Paper 12

A student observed some cells using a microscope with an eyepiece graticule. X They then replaced the slide containing the cells with a stage micrometer with a millimetre scale, and lined up the eyepiece graticule as shown. graticule 0.1 0.2 stage micrometer What is the maximum diameter of the cell labelled X?

Which structures will be present in a cell that causes cholera? circular DNA cytoplasmic DNA

70S ribosomes

ribosome

The electron micrograph shows a section through a cell. What would be present in this type of cell? mitochondria peptidoglycan cell wall histone proteins

A student carried out four tests for biological molecules. The observations are shown in the table. test observations iodine orange biuret purple Benedict’s orange emulsion clear The diagrams show molecules or parts of molecules. Which pair is present in the solution? O OH H H

The diagram shows some relationships between features of carbohydrates. α-glucose 1,4 bonds highly branched Which row correctly matches the carbohydrate with some of its features?

The diagram shows a triglyceride molecule. O

Enzyme P has been found in a tropical grass. ● The enzyme catalyses the hydrolysis of the fungal polysaccharide, chitin, into amino sugars. ● It also inhibits the activity of an enzyme in locust guts which catalyses the digestion of amylose. Which row describes the actions of enzyme P? reaction catalysed reaction inhibited

Which bonds between amino acids hold the shape of the secondary structure and also the tertiary structure of proteins?

Resilin is a protein found in the wings of insects. It is an elastic, fibrous protein and scientists have suggested that it may have an important role in allowing the wings of an insect to fold and unfold without damage. Peptidyl transferase is an enzyme which catalyses the condensation of amino acids during translation to form resilin. Which statements are correct? Peptidyl transferase and resilin have structural roles in the insect. Peptidyl transferase is a globular protein. Peptidyl transferase is soluble in water.

Collagen is a protein that helps to strengthen and increase the elasticity and hydration of the skin. Aging can lead to dry skin and the formation of wrinkles, due to the body producing less collagen. Which row is correct for the structure of collagen in the skin? every fourth amino acid is glycine fibrous protein

What is the effect of an enzyme in an enzyme-catalysed reaction?

How is the Michaelis–Menten constant (Km) used?

Some students investigated the effect of pH on the rate of starch digestion by amylase at 20 °C. ● They added 2 cm3 of a 1% amylase solution and 1 cm3 of pH 4 buffer to a test-tube. ● They added 2 cm3 of a starch solution, containing 0.02 g of starch, to the test-tube. ● They measured the time taken for the starch to be digested (to disappear). The students then repeated these steps with pH 5, pH 6, pH 7 and pH 8 buffers. The table shows the results. pH time taken for starch to be digested / minutes 4.0 1.5 1.0 2.5 6.0 Which graph is correct for these data? pH

Which statements are correct for a non-competitive inhibitor of enzyme action? Increasing the concentration of the enzyme’s substrate will reduce its effect. It reduces the activation energy required for a reaction to take place. It reduces the maximum rate of reaction.

What can increase the fluidity of the cell surface membrane at low temperatures? double bonds between carbon atoms in the fatty acid chains cholesterol fatty acids having shorter chains

Which statements about the proteins and glycoproteins in cell surface membranes are correct? They can allow cells to bond together to form tissues. They can recognise messenger molecules like hormones. They can be antigens and allow cell-to-cell recognition.

In an experiment, four different-sized cubes of colourless agar were placed into a blue dye. The time taken for each cube to turn blue was recorded. Which row shows the surface area and volume of the cube that took the longest time to turn completely blue? surface area / cm2 volume / cm3

The stalk of a dandelion flower is a hollow tube called a scape. Pieces of the scape are cut as shown by the dotted lines and placed in sucrose solutions of different water potentials. hollow centre of scape thick-walled outer cells thin-walled inner cells cuts Which diagram shows the piece that is placed in the sucrose solution with the highest water potential?

Telomeres prevent the loss of genes during DNA replication. Which row correctly shows cell types that contain telomeres? typical animal cell typical plant cell typical bacterial cell

Which events listed are part of mitosis? interphase prophase cytokinesis

The photomicrograph shows 17 cells in different stages of the mitotic cell cycle. cell 1 Which row is correct for this photomicrograph? the role of a centromere in cell 1 the proportion of the cells in the photomicrograph in telophase

The flow diagram shows some of the stages in the replication of a lagging strand of DNA. Which stage of DNA replication uses the enzyme DNA ligase? The DNA double helix begins to unwind. The single strands of DNA are exposed. New complementary DNA fragments are synthesised in the 5′ to 3′ direction. The fragments of newly formed DNA are linked together.

In a gene, the 20 common amino acids are each coded for by three bases in adjacent nucleotides. Why is there a difference between the number of amino acids and the number of possible triplet codes?

How is a primary transcript modified to form mRNA?

The diagram shows protein synthesis in a prokaryote. tRNA 1 tRNA 2 AUG–CCU–AAG–UUG–CCC– DNA cell wall mRNA X Y NOT TO SCALE Which row is correct for molecule X, structure Y and the anticodon of tRNA 1? molecule X structure Y anticodon of tRNA 1

The photomicrographs show sections of two organs of a plant. Which letter identifies a cell found with companion cells in a tissue in a root?

Which row correctly describes the pressure in the xylem and the water potential in the root hair cells used in the transport of water in a transpiring plant? pressure in the xylem water potential in root hair cells

Which row correctly identifies the definitions for each of the key terms used in transpiration? attraction between water molecules and walls of the xylem vessel effect created by evaporation of water from the surface of the leaf

Which combination of features is characteristic of a phloem sieve tube element immediately after it is loaded from a source? water potential of the phloem sieve tube element lignification of the cell wall

Which blood vessel carries blood with the lowest pressure?

The photomicrograph shows cells found in mammalian blood. P What is cell P?

The diagram shows the Bohr shift in actively respiring cells. 100 partial pressure of oxygen / kPa percentage saturation of haemoglobin with oxygen L M What causes the shift from L to M?

The bar chart shows the mean thickness of the walls of the main chambers in a mammalian heart. mean wall thickness / mm heart chamber P Q R S Which row correctly identifies the heart chambers? right atrium left atrium right ventricle left ventricle

The diagram shows parts of the gas exchange system in humans and the associated cells or structures. alveolus bronchiole bronchus trachea ciliated cells squamous epithelial cells C-shaped rings of cartilage ciliated cells and goblet cells Which diagram shows the lines that correctly match the parts to their cells or structures?

The photomicrograph shows the wall of a bronchus as seen with a light microscope. X Y Z Which row correctly identifies the structures labelled? X Y Z

Which factors affect the global pattern of distribution of malaria? the disease is mainly restricted to tropical and subtropical environments the effective vaccine has eradicated the disease in many countries the vector required for transmission of malaria parasites

Which molecule could be a self antigen?

The diagram shows an antibody molecule with some parts labelled. V U Q R P S W T Which row is correct about the parts that form an antigen-binding site and have identical amino acid sequences? form an antigen-binding site have identical amino acid sequences