A-Level Biology Practice Test 2 – 60 Questions with Answers (Cambridge 9700)
Test your A-Level understanding across all 19 topics, using each answer explanation to close any gaps before the next test.
Cell structure
Q1. Which structure is present in plant cells but absent from animal cells?
- (A) A mitochondrion
- (B) A chloroplast
- (C) A ribosome
- (D) A Golgi apparatus
Show Answer
Answer: B – Chloroplasts carry out photosynthesis in plant cells, while animal cells lack them.
Q2. A cell with a very high rate of protein synthesis has a particularly large nucleolus. Why does this correlation make sense?
- (A) It stores starch grains for energy
- (B) It controls entry through nuclear pores
- (C) It synthesises ATP for the cell
- (D) It produces ribosomal RNA and assembles ribosome subunits needed for protein synthesis
Show Answer
Answer: D – The nucleolus is the site of rRNA production and ribosome assembly, so active protein synthesis needs a large nucleolus.
Q3. Which organelle contains enzymes that break down worn-out organelles inside a cell?
- (A) The lysosome, with hydrolytic enzymes
- (B) The ribosome, for lipid synthesis
- (C) The smooth endoplasmic reticulum, for protein synthesis
- (D) The mitochondrion, for photosynthesis
Show Answer
Answer: A – Lysosomes contain hydrolytic enzymes that digest material, including worn-out organelles, within the cell.
Biological molecules
Q4. Which carbohydrate is the main storage polysaccharide in animals?
- (A) Cellulose
- (B) Amylose
- (C) Glycogen
- (D) Chitin
Show Answer
Answer: C – Glycogen is highly branched, allowing rapid glucose release when needed.
Q5. Why do unsaturated fatty acids have lower melting points than saturated fatty acids?
- (A) They have longer carbon chains
- (B) They contain glycerol only
- (C) Double bonds create kinks that prevent tight packing
- (D) They form more hydrogen bonds
Show Answer
Answer: C – Kinks reduce intermolecular forces, so less energy is needed to melt the lipid.
Q6. What is formed when two amino acids join by condensation?
- (A) A dipeptide and water
- (B) A disaccharide and water
- (C) A triglyceride and glycerol
- (D) A nucleotide and phosphate
Show Answer
Answer: A – A peptide bond forms between the amino acids, releasing a water molecule.
Enzymes
Q7. A competitive inhibitor is added to an enzyme reaction. What happens to Km?
- (A) Km decreases because affinity rises
- (B) Vmax decreases permanently
- (C) The optimum pH changes to neutral
- (D) Km increases because more substrate is needed for half Vmax
Show Answer
Answer: D – The inhibitor competes for the active site, so higher substrate concentration is needed to reach half Vmax.
Q8. Which statement about enzyme specificity is correct?
- (A) All enzymes act on glucose
- (B) An enzyme catalyses only reactions of substrates fitting its active site
- (C) Enzymes are unchanged by pH
- (D) Enzymes work equally well on any similar molecule
Show Answer
Answer: B – Specificity arises from the complementary shape of the active site and substrate.
Q9. Why does a protease denatured by strong acid lose activity?
- (A) Its peptide bonds are used as substrate
- (B) It becomes a competitive inhibitor
- (C) Its substrate concentration falls
- (D) Its tertiary structure changes, altering the active site
Show Answer
Answer: D – Acid disrupts bonds holding the tertiary structure, so the active site no longer fits the substrate.
Cell membranes and transport
Q10. Which molecule increases membrane fluidity at low temperatures?
- (A) Glycoprotein
- (B) Cellulose
- (C) Cholesterol prevents tight packing of phospholipids
- (D) Starch
Show Answer
Answer: C – Cholesterol disrupts regular packing, keeping the membrane fluid when cold.
Q11. Which process moves large molecules out of a cell in vesicles?
- (A) Facilitated diffusion
- (B) Exocytosis
- (C) Osmosis
- (D) Active transport through a channel
Show Answer
Answer: B – Vesicles fuse with the membrane and release their contents outside the cell.
Q12. A plant cell in a concentrated sucrose solution becomes plasmolysed. What has happened?
- (A) Water left the vacuole by osmosis and the membrane pulled away from the wall
- (B) Water entered by osmosis
- (C) The cell wall dissolved
- (D) Sucrose entered by active transport
Show Answer
Answer: A – Water moves out down its water potential gradient, shrinking the protoplast.
Q13. Which statement about facilitated diffusion is correct?
- (A) It uses channel or carrier proteins but requires no ATP
- (B) It moves substances against a gradient using ATP
- (C) It only transports water
- (D) It requires vesicle formation
Show Answer
Answer: A – Facilitated diffusion is passive movement down a gradient aided by proteins.
The mitotic cell cycle
Q14. What happens during the S phase of interphase?
- (A) Chromosomes separate
- (B) DNA replicates
- (C) Cytokinesis occurs
- (D) Spindle fibres form
Show Answer
Answer: B – DNA replication in S phase doubles the genetic material before division.
Q15. Which statement about stem cells is correct?
- (A) They cannot divide after birth
- (B) They are only found in plants
- (C) They can divide and differentiate into specialised cells
- (D) They always divide by meiosis
Show Answer
Answer: C – Stem cells retain the ability to self-renew and differentiate.
Q16. What is the role of telomeres?
- (A) They code for spindle proteins
- (B) They trigger cytokinesis
- (C) They attach chromatids to the spindle
- (D) They protect chromosome ends from shortening during replication
Show Answer
Answer: D – Telomeres are repeated sequences that buffer coding DNA against loss.
Q17. During metaphase, chromosomes align at which position?
- (A) The poles of the cell
- (B) Inside the nucleus only
- (C) At the cell membrane
- (D) The equator of the cell
Show Answer
Answer: D – Spindle fibres attach to centromeres and align chromosomes at the equator.
Nucleic acids and protein synthesis
Q18. Which base pairing occurs in DNA?
- (A) Adenine pairs with thymine
- (B) Adenine pairs with uracil
- (C) Guanine pairs with adenine
- (D) Cytosine pairs with thymine
Show Answer
Answer: A – Complementary base pairing in DNA is A-T and C-G.
Q19. What is the function of mRNA?
- (A) It carries amino acids
- (B) It forms part of the ribosome structure
- (C) It carries the genetic code from the nucleus to the ribosome
- (D) It unwinds DNA
Show Answer
Answer: C – Messenger RNA is the template for polypeptide synthesis.
Q20. In the lac operon, what happens when lactose is present?
- (A) The repressor binds the operator permanently
- (B) The repressor is inactivated and transcription proceeds
- (C) RNA polymerase is destroyed
- (D) The structural genes are deleted
Show Answer
Answer: B – Lactose binds the repressor, freeing the operator for transcription.
Q21. Which mutation is most likely to alter a protein significantly?
- (A) A silent substitution in the third base of a codon
- (B) A frameshift mutation from a base insertion
- (C) A substitution that codes for the same amino acid
- (D) A mutation in a non-coding region
Show Answer
Answer: B – Frameshifts change every downstream codon, usually altering the protein greatly.
Transport in plants
Q22. Which tissue transports sucrose in a plant?
- (A) Xylem
- (B) Cortex
- (C) Phloem
- (D) Epidermis
Show Answer
Answer: C – Phloem sieve tubes carry assimilates from sources to sinks.
Q23. What is the effect of high humidity on transpiration rate?
- (A) It decreases transpiration
- (B) It increases transpiration
- (C) It has no effect
- (D) It stops photosynthesis
Show Answer
Answer: A – Humid air reduces the water potential gradient, slowing evaporation from leaves.
Q24. Which feature helps a leaf reduce water loss?
- (A) A large number of open stomata in bright light
- (B) Thin leaves with no cuticle
- (C) Stomata on the upper surface only
- (D) A thick waxy cuticle
Show Answer
Answer: D – A waxy cuticle reduces evaporation from the leaf surface.
Transport in mammals
Q25. Which chamber of the heart has the thickest muscle wall?
- (A) The right atrium
- (B) The left atrium
- (C) The left ventricle
- (D) The right ventricle
Show Answer
Answer: C – The left ventricle must generate high pressure to pump blood around the body.
Q26. Blood pressure in the aorta is about 120 mmHg during systole and falls to about 80 mmHg during diastole, yet capillary flow remains steady. Which arterial feature most directly explains this smoothing?
- (A) Arteries allow exchange with tissues
- (B) Arteries carry blood at uniformly low pressure
- (C) Arteries prevent backflow only, using valves
- (D) Arteries have thick elastic walls that stretch and recoil, maintaining pressure between heartbeats
Show Answer
Answer: D – Elastic walls stretch and recoil, maintaining pressure between heartbeats and smoothing pulsatile flow.
Q27. What is the function of valves in veins?
- (A) To increase blood pressure
- (B) To prevent backflow of blood
- (C) To filter blood
- (D) To carry oxygenated blood
Show Answer
Answer: B – Valves ensure one-way flow in low-pressure veins.
Gas exchange
Q28. Which structure in insects is the site of gas exchange with tissues?
- (A) Tracheoles
- (B) Spiracles only
- (C) Alveoli
- (D) Gills
Show Answer
Answer: A – Tracheoles deliver gases directly to respiring cells.
Q29. A spirometer trace shows lung volume rising sharply over two seconds. Which muscle action is occurring at that moment?
- (A) The diaphragm contracts and flattens, and the external intercostal muscles contract to raise the ribs
- (B) The diaphragm relaxes and domes upwards
- (C) All respiratory muscles stop moving
- (D) The diaphragm pushes air out of the lungs
Show Answer
Answer: A – Contraction of the diaphragm and external intercostals increases thoracic volume, lowering pressure and drawing air in.
Q30. Why is the oxygen dissociation curve for myoglobin to the left of haemoglobin?
- (A) Myoglobin carries four oxygen molecules
- (B) Myoglobin releases oxygen more easily
- (C) Myoglobin is found in blood plasma
- (D) Myoglobin has a higher affinity for oxygen
Show Answer
Answer: D – High affinity allows myoglobin to take up oxygen from haemoglobin in muscles.
Infectious diseases
Q31. A traveller returning from a tropical region develops recurring fever and anaemia. Blood tests show parasites inside red blood cells. Which organism is the most likely cause?
- (A) Vibrio cholerae
- (B) Mycobacterium tuberculosis
- (C) Plasmodium, a protoctist
- (D) Human immunodeficiency virus
Show Answer
Answer: C – Plasmodium is transmitted by Anopheles mosquitoes and infects red blood cells, causing recurring fever.
Q32. How does tuberculosis spread between people?
- (A) Through contaminated water only
- (B) Through airborne droplets from coughing
- (C) Through insect bites
- (D) Through sexual contact only
Show Answer
Answer: B – Droplets containing the bacterium are inhaled by another person.
Q33. Which measure best reduces cholera transmission?
- (A) Vaccinating against viruses only
- (B) Providing clean water and sanitation
- (C) Increasing antibiotic use in healthy people
- (D) Isolating all patients permanently
Show Answer
Answer: B – Clean water breaks the faecal-oral transmission route.
Immunity
Q34. What is the role of phagocytes in immunity?
- (A) They engulf and digest pathogens
- (B) They produce antibodies
- (C) They form memory cells only
- (D) They activate B cells directly by secreting antibodies
Show Answer
Answer: A – Phagocytes carry out non-specific ingestion and digestion of foreign particles.
Q35. A person recovers from chickenpox and is unlikely to develop it again. Which feature of their immune system provides this long-term protection?
- (A) Immunity from injected antibodies
- (B) Immunity that lasts only a few weeks
- (C) Immunity inherited from a parent
- (D) Memory cells produced after exposure to an antigen, giving a rapid response on re-exposure
Show Answer
Answer: D – Active immunity involves the person’s own immune response and memory, providing long-term protection.
Q36. Why does a vaccine need to contain an antigen, rather than simply injecting antibodies, to give long-lasting protection?
- (A) It injects ready-made antibodies for long-term protection
- (B) It prevents all infections permanently
- (C) An antigen triggers the person’s own immune response and memory cell formation
- (D) It works only against bacteria
Show Answer
Answer: C – Vaccination triggers a primary response and memory without causing disease, unlike injected antibodies which give only short-term passive protection.
Energy and respiration
Q37. Where does glycolysis occur?
- (A) In the mitochondrial matrix
- (B) On the inner mitochondrial membrane
- (C) In the nucleus
- (D) In the cytoplasm
Show Answer
Answer: D – Glycolysis splits glucose to pyruvate in the cytoplasm.
Q38. How many ATP molecules are produced per glucose by substrate-level phosphorylation in glycolysis alone, net?
- (A) 4 ATP
- (B) 2 ATP
- (C) 32 ATP
- (D) 0 ATP
Show Answer
Answer: B – Glycolysis produces 4 ATP gross and uses 2 ATP, giving a net gain of 2.
Q39. Why does anaerobic respiration in muscle produce less ATP than aerobic respiration?
- (A) Glucose is only partly broken down to lactate
- (B) No ATP is produced at all
- (C) Oxygen is used in glycolysis
- (D) Lactate contains no energy
Show Answer
Answer: A – Incomplete breakdown leaves much energy in lactate.
Photosynthesis
Q40. Where do the light-dependent reactions occur?
- (A) In the stroma
- (B) In the cytoplasm
- (C) On the thylakoid membranes
- (D) On the mitochondrial cristae
Show Answer
Answer: C – Photosystems and ATP synthase are located in thylakoid membranes.
Q41. What is the first stable product of carbon fixation in C3 plants?
- (A) Glucose
- (B) Ribulose bisphosphate
- (C) Glycerate 3-phosphate
- (D) Pyruvate
Show Answer
Answer: C – Rubisco produces two molecules of glycerate 3-phosphate per carbon dioxide fixed.
Q42. Why does photosynthesis slow at very high temperatures?
- (A) Chlorophyll is destroyed instantly
- (B) Enzymes in the Calvin cycle denature
- (C) Light intensity always falls
- (D) Stomata open wider
Show Answer
Answer: B – Denaturation reduces the rate of Calvin cycle reactions.
Homeostasis
Q43. Which process returns most glucose to the blood in the kidney?
- (A) Ultrafiltration in the glomerulus
- (B) Secretion in the collecting duct
- (C) Filtration in the loop of Henle
- (D) Selective reabsorption in the proximal convoluted tubule
Show Answer
Answer: D – Glucose is reabsorbed by active transport in the proximal tubule.
Q44. Blood glucose rises after a meal, insulin is released, and glucose levels fall back toward normal. Which type of control system is this an example of?
- (A) Negative feedback, which reverses a change to restore a set point
- (B) Positive feedback, which amplifies a change
- (C) A system that stops all hormone secretion
- (D) A system that only operates in the kidney
Show Answer
Answer: A – Negative feedback corrects deviations from the normal range, restoring the set point.
Q45. Which hormone is released when blood glucose rises after a meal?
- (A) Insulin
- (B) Glucagon
- (C) ADH
- (D) Adrenaline
Show Answer
Answer: A – Insulin promotes uptake and storage, lowering blood glucose.
Control and coordination
Q46. A touch receptor in the skin is stimulated. Which neurone carries the impulse first, toward the spinal cord?
- (A) A motor neurone
- (B) A relay neurone only
- (C) A sensory neurone
- (D) An effector neurone
Show Answer
Answer: C – Sensory neurones transmit impulses from receptors towards the central nervous system.
Q47. What is the resting potential of a neurone maintained by?
- (A) Opening of all sodium channels
- (B) Continuous action potentials
- (C) Myelin alone
- (D) The sodium-potassium pump and differential permeability
Show Answer
Answer: D – The pump maintains ion gradients that create the resting potential.
Q48. Which plant hormone promotes cell elongation in shoots?
- (A) Abscisic acid
- (B) Auxin
- (C) Ethene
- (D) Cytokinin only
Show Answer
Answer: B – Auxin accumulates on the shaded side, causing bending towards light.
Inheritance
Q49. In ABO blood groups, a person with genotype IAIB has both A and B antigens on red blood cells. Which type of inheritance does this illustrate?
- (A) One allele masks another completely
- (B) Codominance, in which both alleles are fully expressed in the heterozygote
- (C) Only one allele is inherited
- (D) Alleles are never expressed together
Show Answer
Answer: B – In codominance, both phenotypes appear in the heterozygote, as with A and B antigens together.
Q50. Why do linked genes not show independent assortment?
- (A) They are on different chromosomes
- (B) They are always dominant
- (C) They are sex-linked only
- (D) They are on the same chromosome
Show Answer
Answer: D – Linked genes tend to be inherited together unless crossing over separates them.
Q51. What does a chi-squared test assess?
- (A) The exact genotype of every individual
- (B) The mutation rate in a population
- (C) Whether observed results differ significantly from expected results
- (D) Whether a trait is dominant
Show Answer
Answer: C – Chi-squared compares observed and expected data to test a hypothesis.
Selection and evolution
Q52. Which statement describes stabilising selection?
- (A) It favours the intermediate phenotype
- (B) It favours both extremes
- (C) It always creates new species
- (D) It eliminates all variation
Show Answer
Answer: A – Stabilising selection reduces variation around the mean.
Q53. In a small population, an allele that gives no advantage becomes much more common over ten generations purely by chance. Which process best explains this change?
- (A) Selection for the fittest phenotype
- (B) Mutation caused by selection
- (C) Migration between large populations
- (D) Genetic drift, a random change in allele frequencies, especially in small populations
Show Answer
Answer: D – Chance events can strongly affect allele frequencies in small populations, without any selective advantage.
Q54. Which evidence supports evolution from the fossil record?
- (A) Transitional forms showing gradual change over time
- (B) Identical fossils in all rock layers
- (C) Fossils that never change
- (D) Fossils found only in one location
Show Answer
Answer: A – Transitional fossils link ancestral and descendant forms.
Classification, biodiversity and conservation
Q55. Which group includes organisms that can interbreed to produce fertile offspring?
- (A) A kingdom
- (B) A species
- (C) A phylum
- (D) A domain
Show Answer
Answer: B – The biological species concept is based on reproductive isolation.
Q56. Why is biodiversity important for ecosystems?
- (A) It reduces the number of food chains
- (B) It makes ecosystems more vulnerable
- (C) It increases stability and resilience to change
- (D) It prevents nutrient cycling
Show Answer
Answer: C – Diverse ecosystems have more interactions and alternative pathways.
Q57. Which human activity most directly causes habitat loss?
- (A) Deforestation for agriculture
- (B) Captive breeding
- (C) Seed banking
- (D) Ecotourism only
Show Answer
Answer: A – Clearing land removes habitats and fragments populations.
Genetic technology
Q58. What is the role of primers in PCR?
- (A) They cut DNA at specific sites
- (B) They join DNA fragments
- (C) They provide a starting point for DNA polymerase
- (D) They separate DNA by size
Show Answer
Answer: C – Primers anneal to target sequences and allow polymerase to extend.
Q59. Why are restriction enzymes used in genetic engineering?
- (A) They join DNA fragments together
- (B) They cut DNA at specific recognition sequences
- (C) They amplify DNA
- (D) They sequence DNA bases
Show Answer
Answer: B – Specific cuts create sticky ends for inserting genes.
Q60. What is gene therapy?
- (A) Cloning an entire organism
- (B) Creating a new species
- (C) Removing all genes from a cell
- (D) Introducing a functional gene to treat a genetic disorder
Show Answer
Answer: D – Gene therapy aims to replace or supplement a faulty gene.
Work through any questions you missed again, then revise those areas before moving on to the next test.
📥 Prefer pen and paper? Take this test offline.
Download Printable PDF – Test 2
Free printable version: all 60 questions + answer key. Explanations stay here on the website.