Cambridge A Level Biology 9700 — 2025 Oct/Nov Paper 1 · Variant 2

This document has 24 pages. Any blank pages are indicated. IB25 11_9700_12/5RP © UCLES 2025 [Turn over *3055168285* Cambridge International AS & A Level BIOLOGY 9700/12 Paper 1 Multiple Choice October/November 2025 1 hour 15 minutes You must answer on the multiple choice answer sheet. You will need: Multiple choice answer sheet Soft clean eraser Soft pencil (type B or HB is recommended) INSTRUCTIONS  There are forty questions on this paper. Answer all questions.  For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the multiple choice answer sheet.  Follow the instructions on the multiple choice answer sheet.  Write in soft pencil.  Write your name, centre number and candidate number on the multiple choice answer sheet in the spaces provided unless this has been done for you.  Do not use correction fluid.  Do not write on any bar codes.  You may use a calculator. INFORMATION  The total mark for this paper is 40.  Each correct answer will score one mark.  Any rough working should be done on this question paper.

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3 © UCLES 2025 9700/12/O/N/25 [Turn over 1 A student observed some cells using a microscope with an eyepiece graticule. 0 10 20 30 40 50 60 70 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. 0 10 20 30 40 graticule 0 0.1 0.2 stage micrometer What is the maximum diameter of the cell labelled X? A 0.0066 m B 66 m C 73 m D 733 m 2 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 3 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

4 © UCLES 2025 9700/12/O/N/25 4 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. organelle time taken for 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 reticulum lysosome C rough endoplasmic reticulum Golgi body lysosome D rough endoplasmic reticulum lysosome Golgi body

5 © UCLES 2025 9700/12/O/N/25 [Turn over 5 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    key B     = present C     = not present D   

6 © UCLES 2025 9700/12/O/N/25 6 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 C N C O C CH2 HO C CH2 H H N C H H H N O C CH3 C HO O H H C O C O R H C O C O R H C O– O P O O R H H H OH HO CH2OH C H H OH C C OH H O C C H H H H OH C CH2OH C OH C C H O O H O C H H H C CH2OH C OH C C OH H O C 1 2 3 4 A 1 and 2 B 1 and 3 C 2 and 3 D 3 and 4

7 © UCLES 2025 9700/12/O/N/25 [Turn over 7 The diagram shows some relationships between features of carbohydrates. 1 3 2 α-glucose 1,4 bonds 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 8 The diagram shows a triglyceride molecule. O C O CH2 O C O CH O C O CH2 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.

8 © UCLES 2025 9700/12/O/N/25 9 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 10 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 11 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

9 © UCLES 2025 9700/12/O/N/25 [Turn over 12 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 A   key B    = correct C    = not correct D   13 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 14 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

10 © UCLES 2025 9700/12/O/N/25 15 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 4.0 5 1.5 6 1.0 7 2.5 8 6.0 Which graph is correct for these data?

11 © UCLES 2025 9700/12/O/N/25 [Turn over 4 5 6 pH A 7 8 6 5 4 3 2 1 0 rate of starch digestion by amylase / minutes 4 5 6 pH B 7 8 360 300 240 180 120 60 0 rate of starch digestion by amylase / seconds 4 5 6 pH C D 7 8 20 15 10 5 0 rate of starch digestion by amylase / mg min–1 400 350 300 250 200 150 100 50 0 rate of starch digestion by amylase / mg s–1 4 5 6 pH 7 8 16 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

12 © UCLES 2025 9700/12/O/N/25 17 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 18 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 19 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 A 6.0 1 B 9.5 2 C 12.5 3 D 38.0 16

13 © UCLES 2025 9700/12/O/N/25 [Turn over 20 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? C D A B outer cells inner cells outer cells inner cells outer cells inner cells outer cells inner cells 21 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 A    key B     = present C     = not present D    22 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

14 © UCLES 2025 9700/12/O/N/25 23 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 A attaches daughter chromosomes to spindle fibres > 0.2 B holds sister chromatids together > 0.2 C attaches daughter chromosomes to spindle fibres < 0.2 D holds sister chromatids together < 0.2 24 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. A B C D

15 © UCLES 2025 9700/12/O/N/25 [Turn over 25 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. 26 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.

16 © UCLES 2025 9700/12/O/N/25 27 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 A amino acid 80S ribosome AAC B polypeptide 80S ribosome UUG C polypeptide 70S ribosome AAC D protein 70S ribosome UUG

17 © UCLES 2025 9700/12/O/N/25 [Turn over 28 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? A B C D 29 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 A positive negative B positive positive C negative negative D negative positive 30 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 A cohesion adhesion B adhesion tension C cohesion tension D tension cohesion

18 © UCLES 2025 9700/12/O/N/25 31 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 A higher than source not present B higher than source present C lower than source not present D lower than source present 32 Which blood vessel carries blood with the lowest pressure? A aorta B pulmonary artery C pulmonary vein D vena cava 33 The photomicrograph shows cells found in mammalian blood. P What is cell P? A lymphocyte B monocyte C neutrophil D red blood cell

19 © UCLES 2025 9700/12/O/N/25 [Turn over 34 The diagram shows the Bohr shift in actively respiring cells. 100 80 60 40 20 0 0 2 4 6 8 10 partial pressure of oxygen / kPa percentage saturation of haemoglobin with oxygen L M 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.

20 © UCLES 2025 9700/12/O/N/25 35 The bar chart shows the mean thickness of the walls of the main chambers in a mammalian heart. 14 12 10 8 6 4 2 0 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 A R Q S P B Q S R P C R Q P S D Q R S P

21 © UCLES 2025 9700/12/O/N/25 [Turn over 36 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? A B C D

22 © UCLES 2025 9700/12/O/N/25 37 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 38 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   

23 © UCLES 2025 9700/12/O/N/25 39 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 40 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 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

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This document consists of 3 printed pages. © Cambridge University Press & Assessment 2025 [Turn over Cambridge International AS & A Level BIOLOGY 9700/12 Paper 1 Multiple Choice October/November 2025 MARK SCHEME Maximum Mark: 40 Published This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge International will not enter into discussions about these mark schemes. Cambridge International is publishing the mark schemes for the October/November 2025 series for most Cambridge IGCSE, Cambridge International A and AS Level components, and some Cambridge O Level components.

9700/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2025 © Cambridge University Press & Assessment 2025 Page 2 of 3 Question Answer Marks 1 C 1 2 A 1 3 A 1 4 C 1 5 B 1 6 B 1 7 B 1 8 D 1 9 B 1 10 C 1 11 D 1 12 C 1 13 B 1 14 B 1 15 C 1 16 D 1 17 A 1 18 A 1 19 D 1 20 A 1 21 B 1 22 D 1 23 A 1 24 D 1 25 B 1 26 D 1 27 C 1 28 B 1

9700/12 Cambridge International AS & A Level – Mark Scheme PUBLISHED October/November 2025 © Cambridge University Press & Assessment 2025 Page 3 of 3 Question Answer Marks 29 C 1 30 B 1 31 C 1 32 D 1 33 A 1 34 A 1 35 D 1 36 A 1 37 C 1 38 C 1 39 D 1 40 C 1