Biology 9700/12 October/November 2025: question paper and mark scheme

Question

A student observed some cells using a microscope with an eyepiece graticule. X 0 10 20 30 40 50 60 70 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 10 20 30 40 stage micrometer 0 0.1 0.2 What is the maximum diameter of the cell labelled X? A 0.0066 μm B 66 μm C 73 μm D 733 μm

Question

Which structures will be present in a cell that causes cholera? 1 circular DNA 2 cytoplasmic DNA 3 70S ribosomes A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Question

Which organelles have a partially permeable membrane? 1 Golgi apparatus 2 lysosome 3 mitochondrion 4 ribosome A 1, 2 and 3 B 1, 2 and 4 C 1, 3 and 4 D 2, 3 and 4

Question

Mouse cells were grown in a dish containing a growth medium. Radioactively labelled amino acids were added to the growth medium. The table shows the time taken for the radioactively labelled amino acids to appear in three different organelles, R, S and T. time taken for organelle radioactivity to appear / min R 2 S 9 T 35 Which row correctly identifies the organelles? R S T A Golgi body lysosome rough endoplasmic reticulum B Golgi body rough endoplasmic lysosome reticulum C rough endoplasmic Golgi body lysosome reticulum D rough endoplasmic lysosome Golgi body reticulum

Question

The electron micrograph shows a section through a cell. What would be present in this type of cell? peptidoglycan mitochondria histone proteins cell wall A key B = present C = not present D

Question

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? H OH HO CH2 C C H OH CH2OH O H O N C C H H C O O HO C CH2 C C H OH H H C C C C H O H OH H N C O O C C H H CH3 C C H CH2OH H OH O N H H 1 2 H O CH2OH H C O C R C O O H H H C C H C O C R OH H HO OH O C C H OH H C O P O R H O– 3 4 A 1 and 2 B 1 and 3 C 2 and 3 D 3 and 4

Question

The diagram shows some relationships between features of carbohydrates. α-glucose 1,4 bonds 1 3 2 highly branched Which row correctly matches the carbohydrate with some of its features? 1 2 3 A amylopectin glycogen amylose B amylose amylopectin cellulose C cellulose glycogen sucrose D glycogen amylose amylopectin

Question

The diagram shows a triglyceride molecule. O CH2 O C O CH O C O CH2 O C Which statement is correct for the structure and function of this triglyceride? A The glycerol head forms hydrogen bonds with water in cytoplasm to produce oil droplets. B The hydrophobic fatty acids allow only small molecules to pass through the cell surface membrane. C It packs closely with identical triglyceride molecules to form energy reserves in lysosomes. D It has long hydrocarbon chains that release high energy output per unit mass when oxidised.

Question

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 A hydrolysis of glycosidic bonds condensation of glycosidic bonds B hydrolysis of glycosidic bonds hydrolysis of glycosidic bonds C hydrolysis of peptide bonds condensation of glycosidic bonds D hydrolysis of peptide bonds hydrolysis of glycosidic bonds

Question

Which bonds between amino acids hold the shape of the secondary structure and also the tertiary structure of proteins? A peptide bonds B disulfide bonds C hydrogen bonds D ionic bonds

Question

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? 1 Peptidyl transferase and resilin have structural roles in the insect. 2 Peptidyl transferase is a globular protein. 3 Peptidyl transferase is soluble in water. A 1 and 2 B 1 and 3 C 1 only D 2 and 3

Question

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 fibrous protein is glycine A key B = correct C = not correct D

Question

What is the effect of an enzyme in an enzyme-catalysed reaction? A decreases the activation energy and decreases the energy yield B decreases the activation energy and has no effect on the energy yield C increases the activation energy and increases the energy yield D decreases the activation energy and increases the energy yield

Question

How is the Michaelis–Menten constant (Km) used? A to determine the number of collisions between the enzyme and substrate B to compare the affinity of enzymes for their substrates C to find the maximum velocity of an enzyme (Vmax) D to find the optimum rate of reaction

Question

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. time taken for starch pH to be digested / minutes 4 4.0 5 1.5 6 1.0 7 2.5 8 6.0 Which graph is correct for these data? A B 6 360 5 300 4 240 rate of starch rate of starch digestion by digestion by amylase 3 amylase 180 / minutes / seconds 2 120 1 60 0 0 4 5 6 7 8 4 5 6 7 8 pH pH C D 20 400 350 15 300 250 rate of starch rate of starch digestion by digestion by amylase 10 amylase 200 –1 –1 / mg min / mg s 150 5 100 50 0 0 4 5 6 7 8 4 5 6 7 8 pH pH

Question

Which statements are correct for a non-competitive inhibitor of enzyme action? 1 Increasing the concentration of the enzyme’s substrate will reduce its effect. 2 It reduces the activation energy required for a reaction to take place. 3 It reduces the maximum rate of reaction. A 1 and 3 B 1 only C 2 and 3 D 3 only

Question

What can increase the fluidity of the cell surface membrane at low temperatures? 1 double bonds between carbon atoms in the fatty acid chains 2 cholesterol 3 fatty acids having shorter chains A 1, 2 and 3 B 1 and 3 only C 1 only D 2 and 3 only

Question

Which statements about the proteins and glycoproteins in cell surface membranes are correct? 1 They can allow cells to bond together to form tissues. 2 They can recognise messenger molecules like hormones. 3 They can be antigens and allow cell-to-cell recognition. A 1, 2 and 3 B 1 and 2 only C 1 and 3 only D 2 and 3 only

Question

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 volume / cm2 / cm3 A 6.0 1 B 9.5 2 C 12.5 3 D 38.0 16

Question

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. thick-walled outer cells hollow centre of scape cuts thin-walled inner cells Which diagram shows the piece that is placed in the sucrose solution with the highest water potential? A B outer cells inner cells inner cells outer cells C D inner cells outer cells outer cells inner cells

Question

Telomeres prevent the loss of genes during DNA replication. Which row correctly shows cell types that contain telomeres? typical typical typical animal cell plant cell bacterial cell A key B = present C = not present D

Question

Which events listed are part of mitosis? 1 interphase 2 prophase 3 cytokinesis A 1, 2 and 3 B 1 and 2 only C 1 only D 2 only

Question

The photomicrograph shows 17 cells in different stages of the mitotic cell cycle. cell 1 Which row is correct for this photomicrograph? the proportion of the cells the role of a centromere in cell 1 in the photomicrograph in telophase A attaches daughter > 0.2 chromosomes to spindle fibres B holds sister chromatids together > 0.2 C attaches daughter < 0.2 chromosomes to spindle fibres D holds sister chromatids together < 0.2

Question

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? A B C D The DNA double The single New complementary DNA The fragments of helix begins strands of DNA fragments are synthesised newly formed DNA to unwind. are exposed. in the 5′ to 3′ direction. are linked together.

Question

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? A 44 triplets have no functions. B Some amino acids are coded for by more than one triplet. C Some triplets have unknown functions. D There are 44 ‘start’ and ‘stop’ triplets.

Question

How is a primary transcript modified to form mRNA? A It becomes longer as exons are joined together. B It becomes shorter as exons are removed. C It becomes longer as introns are joined together. D It becomes shorter as introns are removed.

Question

The diagram shows protein synthesis in a prokaryote. DNA cell wall tRNA 1 tRNA 2 X AUG–CCU–AAG–UUG–CCC– mRNA NOT TO SCALE Y Which row is correct for molecule X, structure Y and the anticodon of tRNA 1? anticodon of molecule X structure Y tRNA 1 A amino acid 80S ribosome AAC B polypeptide 80S ribosome UUG C polypeptide 70S ribosome AAC D protein 70S ribosome UUG

Question

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? C A B D

Question

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 water potential in the xylem root hair cells A positive negative B positive positive C negative negative D negative positive

Question

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

Question

Which combination of features is characteristic of a phloem sieve tube element immediately after it is loaded from a source? water potential of lignification of the phloem sieve the cell wall tube element A higher than source not present B higher than source present C lower than source not present D lower than source present

Question

Which blood vessel carries blood with the lowest pressure? A aorta B pulmonary artery C pulmonary vein D vena cava

Question

The photomicrograph shows cells found in mammalian blood. P What is cell P? A lymphocyte B monocyte C neutrophil D red blood cell

Question

The diagram shows the Bohr shift in actively respiring cells. 100 80 percentage 60 L saturation of haemoglobin M 40 with oxygen 20 0 0 2 4 6 8 10 partial pressure of oxygen / kPa What causes the shift from L to M? A Carbonic acid dissociates to release protons that bind to oxyhaemoglobin, affecting the conformation of haemoglobin to reduce its affinity for oxygen. B Hydrogencarbonate ions produced by carbonic anhydrase alter the charge of oxyhaemoglobin, reducing its ability to bind oxygen. C Hydrogen ions combine with chloride ions in tissue fluid to produce hydrochloric acid, distorting oxyhaemoglobin and causing it to lose bound oxygen. D A low concentration of oxygen in actively respiring cells causes oxyhaemoglobin to release oxygen more quickly down the concentration gradient.

Question

The bar chart shows the mean thickness of the walls of the main chambers in a mammalian heart. 14 12 10 mean wall 8 thickness / mm 6 4 2 0 P Q R S heart chamber Which row correctly identifies the heart chambers? right atrium left atrium right ventricle left ventricle A R Q S P B Q S R P C R Q P S D Q R S P

Question

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

Question

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 A epithelium elastic fibres bronchiole B endothelium smooth muscle bronchiole C epithelium smooth muscle blood vessel D endothelium elastic fibres blood vessel

Question

Which factors affect the global pattern of distribution of malaria? 1 the disease is mainly restricted to tropical and subtropical environments 2 the effective vaccine has eradicated the disease in many countries 3 the vector required for transmission of malaria parasites 1 2 3 A key B = effect C = not an effect D

Question

Which molecule could be a self antigen? A a viral capsid protein B a phospholipid in a viral envelope C a toxin released by a pathogen D a glycoprotein on the surface of a macrophage

Question

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