Biology 2025 May/June Paper 12 | Past Paper

Q2

MCQ 1 mark

Which statement about a light microscope is correct? A As the distance to see two points as separate points decreases, the resolution also decreases. B A bacterium 0.2 C Two membranes that are less than 300 nm apart will be visible as two separate membranes if the wavelength of light is 600nm. D The resolution will improve with visible light of a longer wavelength, such as red light.

A

As the distance to see two points as separate points decreases, the resolution also

B

A bacterium 0.2

C

Two membranes that are less than 300

D

The resolution will improve with visible light of a longer wavelength, such as red light.

Q3

Short Answer 1 mark

The electron micrograph shows a cell. ×108 000 What is the actual maximum length of the cell? A 0.509

Q4

MCQ 1 mark

The table compares some biochemical molecules of P, Q, R and S. chlorophyll DNA RNA peptidoglycan P 3 3 3 7 key Q 7 3 3 7 3 = present R 7 3 3 3 7 = not present S 7 7 3 7 Which row correctly identifies P, Q, R and S? P Q R S A chloroplast virus mitochondrion bacterium B chloroplast mitochondrion bacterium virus C mitochondrion virus bacterium chloroplast D virus bacterium mitochondrion chloroplast

A

chloroplast virus mitochondrion bacterium

B

chloroplast mitochondrion bacterium virus

C

mitochondrion virus bacterium chloroplast

D

virus bacterium mitochondrion chloroplast

Q5

Short Answer 1 mark

Which cell structures contain enzymes and are enclosed by a double membrane? 1 nucleus 2 mitochondrion 3 chloroplast A 1, 2 and 3 B 1 and 2 only C 1 only D 2 and 3 only

Q6

MCQ 1 mark

What is the order of size of cell structures? largest smallest A centrioles ribosomes lysosomes nucleoli B centrioles nucleoli lysosomes ribosomes C nucleoli lysosomes centrioles ribosomes D nucleoli centrioles ribosomes lysosomes

A

centrioles ribosomes lysosomes nucleoli

B

centrioles nucleoli lysosomes ribosomes

C

nucleoli lysosomes centrioles ribosomes

D

nucleoli centrioles ribosomes lysosomes

Q7

MCQ 1 mark

A sample of a solution of sucrose tested for reducing sugars remains blue, but when another sample of the same solution is tested for non-reducing sugars the solution turns red. What explains these results? A During the non-reducing sugar test, an acid hydrolyses sucrose to glucose and fructose. B During the non-reducing sugar test, sucrose molecules condense into polysaccharides. C The reducing sugar test converts sucrose into glucose and fructose. D The reducing sugar test hydrolyses monosaccharides to disaccharides.

A

sample of a solution of sucrose tested for reducing sugars remains blue, but when another

A

During the non-reducing sugar test, an acid hydrolyses sucrose to glucose and fructose.

B

During the non-reducing sugar test, sucrose molecules condense into polysaccharides.

C

The reducing sugar test converts sucrose into glucose and fructose.

D

The reducing sugar test hydrolyses monosaccharides to disaccharides.

Q8

Short Answer 1 mark

Which molecules contain at least two double bonds? saturated triglyceride collagen haemoglobin

Q9

MCQ 1 mark

Amylose, amylopectin and glycogen are all polysaccharides. Enzyme X removes one maltose molecule at a time from the ends of a polysaccharide molecule Which row shows how completely each of these molecules will be hydrolysed by enzyme X? (Assume that each polysaccharide is composed of the same number of monomers before hydrolysis begins.) least completely hydrolysed most completely hydrolysed A amylose amylopectin glycogen B amylose glycogen amylopectin C glycogen amylose amylopectin D glycogen amylopectin amylose

A

amylose amylopectin glycogen

B

amylose glycogen amylopectin

C

glycogen amylose amylopectin

D

glycogen amylopectin amylose

Q10

MCQ 1 mark

Which property of water enables sweating to be an efficient means of losing heat from the body? A The latent heat of vaporisation of water is high. B The specific heat capacity of water is high. C Each water molecule can form a hydrogen bond with four water molecules. D The forces of cohesion and adhesion on water molecules are very high.

A

The latent heat of vaporisation of water is high.

B

The specific heat capacity of water is high.

C

Each water molecule can form a hydrogen bond with four water molecules.

D

The forces of cohesion and adhesion on water molecules are very high.

Q11

MCQ 1 mark

Which bonds are found in the levels of structure of a protein molecule? primary structure secondary structure quaternary structure A covalent bond hydrogen bond peptide bond B covalent bond ionic bond disulfide bond C peptide bond hydrogen bond ionic bond D peptide bond ionic bond disulfide bond

A

covalent bond hydrogen bond peptide bond

B

covalent bond ionic bond disulfide bond

C

peptide bond hydrogen bond ionic bond

D

peptide bond ionic bond disulfide bond

Q12

MCQ 1 mark

Prokaryotes and eukaryotes use extracellular enzymes. Extracellular digestive enzymes are found in the external environments of some prokaryotes. Some prokaryotes are digested by hydrolytic enzymes during phagocytosis by eukaryotic cells. Which row shows the locations where extracellular enzymes are produced? site of production of digestive enzymes used by prokaryotes site of production of hydrolytic enzymes used by eukaryotic phagocytes A inside cells inside cells B inside cells outside cells C outside cells inside cells D outside cells outside cells

A

inside cells inside cells

B

inside cells outside cells

C

outside cells inside cells

D

outside cells outside cells

Q13

MCQ 1 mark

Amylase breaks down starch molecules. Which substance will have the same number of molecules for the duration of this reaction? A amylase B water C maltose D amylose

A

amylase

B

water

C

maltose

D

amylose

Q14

Short Answer 1 mark

Which graphs could show the effect of pH on the rate of enzyme-catalysed reactions? rate of reaction rate of reaction rate of reaction rate of reaction 1234 0000 114 14 14 14 A 1 and 2 B 1 and 3 C 2 and 4 D 3 and 4

Q15

MCQ 1 mark

After a heart attack, the enzyme lactate dehydrogenase leaks into the blood plasma from damaged heart muscle. What is required to measure the activity of lactate dehydrogenase activity in a sample of blood plasma? sterilisation of blood plasma by heating incubation of sample with substrate for lactate dehydrogenase incubation of sample with lactate dehydrogenase inhibitor A 3 3 3 key B 7 3 3 3 = required C 7 3 7 7 = not required D 7 7 3

A

3 3 3 key

B

7 3 3 3 = required

C

7 3 7 7 = not required

D

7 7 3

Q16

Short Answer 1 mark

Which graph correctly shows K m and Vmax? concentration of enzyme concentration of substrate rate of reactionmax rate of reactionmax concentration of substrate concentration of enzyme rate of reactionmax rate of reactionmax

Q17

Short Answer 1 mark

Cell membranes become less fluid as the temperature decreases. Bacteria and yeast cannot regulate their cell temperatures. How do bacteria and yeast maintain the fluidity of their cell membranes when the temperature decreases? 1 They increase the numbers of unsaturated fatty acids in their phospholipid molecules. 2 They increase the numbers of saturated fatty acids in their phospholipid molecules. 3 They increase the numbers of cholesterol molecules in their cell membranes. A 1 and 3 B 1 only C 2 and 3 D 2 only

Q18

MCQ 1 mark

Samples X, Y and Z are epidermal tissues cut from an onion. Each epidermal tissue was immersed in one of three different concentrations of a salt solution for 30 minutes. A student observed each tissue sample with a light microscope. Then the student estimated the concentration of each salt solution using a scale. The diagram shows the scale. P, Q and R represent the estimated concentration of the three salt solutions. P Q R distilled water concentrated salt solution The photomicrographs show the appearance of the tissues in samples X, Y and Z. sample X sample Y sample Z Which row shows the estimated concentrations of the salt solutions in which samples Y and Z were immersed? sample Y sample Z A P Q B P R C Q R D R P

A

student observed each tissue sample with a light microscope. Then the student estimated the

A

P Q

B

P R

C

Q R

D

R P

Q19

MCQ 1 mark

The graph shows the results of an osmosis investigation using potato tissue. -10-15-20 percentage change in mass 0 0.2 0.3 0.5 0.6 0.7 0.9 0.1 0.8 concentration of sodium chlorideconcentration of sodium chloride / molmol dmdm -3-3 concentration of sodium chloride / mol dm 0.40.40.4 What is the concentration of sodium chloride solution that has the equivalent water potential to this potato tissue and what is correct about the movement of water at that point? A 0.37 mol dm and no net movement of water B 17 mol dm and net movement of water out of the potato tissue C 0 mol dm and no net movement of water D 0.9 mol dm and net movement of water into the potato tissue

A

0.37 mol dm

B

17 mol dm

C

0 mol dm

D

0.9 mol dm

Q20

Short Answer 1 mark

Some agar was coloured pink using a pH indicator. The pink agar was then used to make three agar cubes with different dimensions. 2 cm × 2 cm × 2 cm4 cm × 4 cm × 4 cm 5 cm × 5 cm × 5 cm The cubes were placed in a beaker and covered with 0.1 mol dm hydrochloric acid. The temperature of the experiment was standardised at 20°C. Hydrochloric acid diffused into the agar cubes causing the cubes to become colourless. What is the surface area to volume ratio of the agar cube that became colourless in the least amount of time? A 0.33 : 1 B 0.83 : 1 C 1.2 : 1 D 3.0 : 1

Q21

Short Answer 1 mark

The diagram shows the arrangement of chromosomes with attached spindle fibres during a stage of mitosis. Which row correctly identifies the stage of mitosis and describes what is happening? stage of mitosis description anaphase chromosomes are being pulled towards the centromeres metaphase sister chromatids are replicating prior to separation metaphase chromosomes are being positioned along the equator of the cell anaphase sister chromatids are being pulled towards the poles of the cell

Q22

Short Answer 1 mark

During which phase of the cell cycle does DNA replication take place?A G 1 B G 2 C M D S

Q23

MCQ 1 mark

Human body cells in interphase have 46 chromosomes. What is correct about the number of telomeres present in prophase of a human body cell? A 46 as there is one telomere at the end of 46 chromosomes B 92 as there is one telomere at each end of 46 chromosomes C 92 as there is one telomere at the end of 92 chromatids D 184 as there is one telomere at each end of 92 chromatids

A

46 as there is one telomere at the end of 46 chromosomes

B

92 as there is one telomere at each end of 46 chromosomes

C

92 as there is one telomere at the end of 92 chromatids

D

184 as there is one telomere at each end of 92 chromatids

Q24

MCQ 1 mark

Sometimes hydrogen bonds form temporarily between the bases of two strands of RNA. How many hydrogen bonds form when guanine and uracil each bind to their complementary base? guanine uracil A 3 3 B 3 2 C 2 3 D 2 2

A

3 3

B

3 2

C

2 3

D

2 2

Q25

Short Answer 1 mark

The table shows all the possible DNA triplet codes for some amino acids. amino acid DNA triplet code cysteine ACA cysteine ACG tryptophan ACC isoleucine TAA isoleucine TAG isoleucine TAT methionine TAC The amino acid sequence is shown. methionine - isoleucine - cysteine - tryptophan What is the maximum number of different DNA sequences that could produce this amino acid sequence? A 1 B 4 C 6 D 7

Q26

Short Answer 1 mark

Which row is correct for transpiration? definition of transpiration comparison of water potential evaporation of water from leaf surfaces higher inside air spaces in the leaf than the air outside evaporation of water from leaf surfaces lower inside air spaces in the leaf than the air outside loss of water vapour from leaves lower inside air spaces in the leaf than the air outside loss of water vapour from leaves higher inside air spaces in the leaf than the air outside

Q27

Short Answer 1 mark

Which features of companion cells and xylem vessel elements make them suitable for their function? companion cells xylem vessel elements transport contents of cell in one direction only lignified walls provide support cellulose walls provide support nuclei allow cell division nuclei allow cell division gaps between cells allow rapid transport numerous mitochondria supply energy absence of cytoplasm allows mass flow

Q28

MCQ 1 mark

The diagram shows some root cells. cell wall vacuole cytoplasmkey pathway of water moving from the soil Which statement is correct for the pathway shown by the arrows? A Water will be blocked by a band of suberin. B Water will move through the Casparian strip. C Water will pass easily through the root endodermis. D Water will pass through plasmodesmata.

A

Water will be blocked by a band of suberin.

B

Water will move through the Casparian strip.

C

Water will pass easily through the root endodermis.

D

Water will pass through plasmodesmata.

Q29

MCQ 1 mark

The graph shows the diameter of a tree trunk at different times. diameter of tree trunk arbitrary units 00:00 12:00 time of day 00:00J L Which statement is correct? A J shows the expansion of the trunk as water fills the xylem during transpiration. B K shows a reduction in diameter of the trunk as water is lost from the phloem due to translocation. C K shows a reduction in diameter of the trunk due to water held in tension in the xylem. D L shows the expansion of the trunk as the phloem tissue acts as a sink at night.

A

J shows the expansion of the trunk as water fills the xylem during transpiration.

B

K shows a reduction in diameter of the trunk as water is lost from the phloem due to

C

K shows a reduction in diameter of the trunk due to water held in tension in the xylem.

D

L shows the expansion of the trunk as the phloem tissue acts as a sink at night.

Q30

Short Answer 1 mark

The plan diagrams of transverse sections of two plant organs are shown. These are not drawn to scale. Which tissues contain proton pumps? A Q and S B Q and T C R and S D R and T

Q31

MCQ 1 mark

The diagrams show three types of blood cells, which are all drawn to the same scale. XYZ nucleus nucleus nucleus Which row shows the characteristics of the cells? name of blood cell X engulfs pathogens by endocytosis each responds to one antigen A monocyte Y Z B monocyte Z Y C lymphocyte Y Z D lymphocyte Z Y

A

monocyte Y Z

B

monocyte Z Y

C

lymphocyte Y Z

D

lymphocyte Z Y

Q32

MCQ 1 mark

The graph shows oxygen dissociation curves for three animals. The shape of each curve is influenced by respiration rate and the affinity of haemoglobin for oxygen. percentage saturation of haemoglobin with oxygen partial pressure of oxygen animal 1 animal 2 animal 3key What can be concluded from the graph? A Animal 1 has haemoglobin adapted to have a higher affinity for oxygen than animal 2. B Animal 3 has haemoglobin adapted to have a higher affinity for oxygen than animal 2. C Animal 3 has haemoglobin adapted to maintain a lower respiration rate than animal 2. D Animal 1 has haemoglobin adapted to maintain a higher respiration rate than animal 2.

A

Animal 1 has haemoglobin adapted to have a higher affinity for oxygen than animal 2.

B

Animal 3 has haemoglobin adapted to have a higher affinity for oxygen than animal 2.

C

Animal 3 has haemoglobin adapted to maintain a lower respiration rate than animal 2.

D

Animal 1 has haemoglobin adapted to maintain a higher respiration rate than animal 2.

Q33

Short Answer 1 mark

Which statements about a mammalian heart are correct? 1 The right atrium and right ventricle contain deoxygenated blood going to the lungs. 2 The left atrium and left ventricle contain oxygenated blood going to the pulmonary circulation. 3 The left ventricle has a thicker wall than the right ventricle and delivers blood at higher pressure. 4 The pressure of blood in the aorta is less than that in the pulmonary artery. A 1, 3 and 4 B 1 and 3 only C 2, 3 and 4 D 2 and 4 only

Q34

MCQ 1 mark

How is most carbon dioxide transported in the blood? A as carbaminohaemoglobin B as carbonic acid C as hydrogencarbonate ions D in solution in cytoplasm

A

as carbaminohaemoglobin

B

as carbonic acid

C

as hydrogencarbonate ions

D

in solution in cytoplasm

Q35

MCQ 1 mark

Which row shows the tissues that are present in the wall of the trachea and the wall of the bronchus? cartilage ciliated epithelium smooth muscle A 3 3 3 key B 3 3 7 3 = present C 3 7 3 7 = not present D 7 3 7

A

3 3 3 key

B

3 3 7 3 = present

C

3 7 3 7 = not present

D

7 3 7

Q36

Short Answer 1 mark

Which factors maintain the diffusion gradient for carbon dioxide at the surface of the alveoli? 1 blood flow around the alveoli 2 breathing movement exchanging air in the lungs 3 thin epithelial lining of the alveoli A 1 and 2 B 1 and 3 C 1 only D 2 and 3

Q37

MCQ 1 mark

A student made notes about two diseases: hand, foot and mouth disease (HFMD) and Lyme disease. HFMD is caused by a viral pathogen and is transmitted in a variety of ways including: Lyme disease is caused by a bacterial pathogen and is transmitted by the bite of an infected insect. Which statement makes a correct comparison between the diseases the student wrote about and cholera, malaria or tuberculosis (TB)? A Antibiotics can be used to kill the vector of the pathogen that causes malaria and the vector of the pathogen that causes Lyme disease. B HFMD can be transmitted in a similiar way to either cholera or TB. C The cells of the pathogen that causes HFMD and the cells of the pathogen that causes TB are prokaryotic. D Transmission of TB and HFMD could be reduced by chlorinating drinking water.

A

student made notes about two diseases: hand, foot and mouth disease (HFMD) and Lyme

A

Antibiotics can be used to kill the vector of the pathogen that causes malaria and the vector

B

HFMD can be transmitted in a similiar way to either cholera or TB.

C

The cells of the pathogen that causes HFMD and the cells of the pathogen that causes TB

D

Transmission of TB and HFMD could be reduced by chlorinating drinking water.

Q38

Short Answer 1 mark

Which statements explain why antibiotics may not treat cholera successfully? 1 The infectious organism has developed resistance to the antibiotic. 2 Antibiotics cannot harm viruses. 3 Antibiotics do not affect pathogens that are eukaryotic. A 1, 2 and 3 B 1 only C 2 only D 3 only

Q39

Short Answer 1 mark

The statements describe the phagocytosis of a bacterium by a macrophage. 1 Digestive enzymes break down the bacterium. 2 Lysosome fuses with the vacuole. 3 Macrophage displays the bacterial antigens on its cell surface membrane. 4 Macrophage engulfs the bacterium and encloses it in a vacuole. 5 Receptors on the cell surface membrane of macrophage bind to the bacterium. Which order is correct for phagocytosis?

Q40

MCQ 1 mark

Two people, G and H, were each given an injection to protect them against a particular pathogen. One person was injected with antibodies. The other person was injected with a vaccine. The graph shows the concentrations of the antibody against this pathogen in the blood of the two people, G and H, during a period of 20 days after their injections. 0510 time / days antibody concentration arbitrary units 15 20 time of injection Which row correctly describes the type of immunity shown by G and H? G H A artificial active immunity artificial passive immunity B artificial passive immunity artificial active immunity C natural active immunity natural passive immunity D natural passive immunity natural active immunity Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Local Examinations Syndicate (UCLES), which is a department of the University of Cambridge.

A

artificial active immunity artificial passive immunity

B

artificial passive immunity artificial active immunity

C

natural active immunity natural passive immunity

D

natural passive immunity natural active immunity

Board	CAIE
Level	A Level
Subject	Biology
Code	`9700`
Year	2025
Session	May/June
Paper No.	Paper 12
Total Marks	40
Duration	75 minutes
Q&A	39 questions

Biology 2025 · May/June · Paper 12

Questions & Model Answers 39 Qs

Paper Details