A-Level Biology Practice Test 19 – 60 Questions with Answers (Cambridge 9700)

Q1. The cytoskeleton in eukaryotic cells is important because it does what?

• (A) Provides structural support, organelle positioning and tracks for vesicle movement
• (B) Synthesises ATP for the cell
• (C) Stores genetic information in the cytoplasm
• (D) Forms the outer cell wall in animal cells

Q2. Which structure is the site of ribosome production in a eukaryotic cell?

• (A) Smooth endoplasmic reticulum
• (B) Nucleolus within the nucleus
• (C) Golgi apparatus
• (D) Lysosome

Q3. Lysosomes are important in phagocytes because they contain what?

• (A) Chlorophyll for photosynthesis
• (B) DNA for protein synthesis
• (C) Hydrolytic enzymes that digest ingested material
• (D) ATP synthase for energy production

Q4. Cellulose is a structural polysaccharide in plant cell walls. Which feature makes it strong?

• (A) Alpha-glucose units joined by 1,4-glycosidic bonds into a helix
• (B) Beta-glucose units joined by 1,4-glycosidic bonds into straight chains held together by hydrogen bonds
• (C) Branched chains with many 1,6-glycosidic bonds
• (D) Alternating glucose and fructose units

Q5. Phospholipids are suited to forming cell membranes because they are what?

• (A) Completely hydrophobic molecules
• (B) Completely hydrophilic molecules
• (C) Amphipathic, with hydrophilic heads and hydrophobic tails that form a bilayer in water
• (D) Large proteins that span the membrane

Q6. A heat-denatured enzyme is cooled slowly, but its catalytic activity does not return. Which explanation best fits this result?

• (A) The sequence of amino acids in the enzyme has been rearranged
• (B) New peptide bonds have formed between different amino acids
• (C) The enzyme has gained extra subunits from the surrounding solution
• (D) Its tertiary structure, held by weak bonds, has unfolded irreversibly and the active site shape is lost

Q7. End-product inhibition is a form of feedback control in metabolic pathways. How does it work?

• (A) The end product denatures all enzymes in the cell permanently
• (B) The end product increases the activity of the first enzyme in the pathway
• (C) The end product acts as a non-competitive inhibitor of an early enzyme in the pathway, slowing its own production
• (D) The end product is converted back into the original substrate

Q8. Why do enzymes show specificity for their substrates?

• (A) All enzymes have identical active sites
• (B) Substrates are all the same shape
• (C) Enzymes bind any molecule that collides with them
• (D) The active site has a specific shape and chemical properties complementary to the substrate

Q9. Which graph shape is expected for enzyme activity against temperature, and why does activity fall after the optimum?

• (A) Activity rises to an optimum as collisions increase, then falls sharply as the enzyme denatures
• (B) Activity falls steadily as temperature rises
• (C) Activity stays constant at all temperatures
• (D) Activity rises steadily with temperature and never falls

Q10. Glycoproteins in the cell surface membrane are important for which function?

• (A) Transporting water through aquaporins
• (B) Providing energy for active transport
• (C) Forming the lipid bilayer itself
• (D) Cell recognition and adhesion, including immune recognition of self cells

Q11. Which molecule can cross the lipid bilayer by simple diffusion most easily?

• (A) A small, non-polar molecule such as oxygen
• (B) A large charged ion such as sodium
• (C) A large polar molecule such as glucose
• (D) A protein such as haemoglobin

Q12. The sodium-potassium pump is an example of active transport because it does what?

• (A) Allows sodium ions to diffuse down their gradient
• (B) Uses ATP to move sodium out and potassium in against their gradients
• (C) Opens a channel for passive movement of both ions
• (D) Transports water molecules by osmosis

Q13. During prophase of mitosis, which changes occur?

• (A) Chromosomes condense, the nuclear envelope breaks down, and spindle fibres form
• (B) Sister chromatids separate to opposite poles
• (C) Chromosomes align on the equator
• (D) The cell divides into two daughter cells

Q14. Telophase of mitosis is characterised by which events?

• (A) Chromosomes condense and spindle fibres appear
• (B) Nuclear envelopes reform and chromosomes decondense
• (C) Sister chromatids are pulled apart
• (D) DNA is replicated

Q15. Cancer may develop when mutations affect genes controlling the cell cycle. Which type of gene, when mutated, fails to stop uncontrolled division?

• (A) A gene for haemoglobin production
• (B) A gene for chlorophyll synthesis
• (C) A tumour suppressor gene, which normally inhibits division or triggers repair or cell death
• (D) A gene for antibody production

Q16. Gene control in eukaryotes often involves transcription factors. What do transcription factors do?

• (A) They copy DNA during replication
• (B) They bind to specific DNA sequences and regulate whether RNA polymerase transcribes a gene
• (C) They translate mRNA into protein at the ribosome
• (D) They cut DNA at restriction sites

Q17. Which statement about the start codon is correct?

• (A) It signals the end of translation
• (B) It is found only in prokaryotic mRNA
• (C) It is AUG, coding for methionine and marking where translation begins
• (D) It codes for the final amino acid in every protein

Q18. A nonsense mutation differs from a missense mutation in that a nonsense mutation does what?

• (A) Changes one amino acid to another
• (B) Leaves the amino acid sequence unchanged
• (C) Deletes an entire gene from the chromosome
• (D) Creates a premature stop codon, truncating the protein

Q19. Which adaptation of root hair cells increases the rate of water uptake?

• (A) Thick lignified walls
• (B) Absence of a cell membrane
• (C) A large surface area from the elongated hair and a thin wall
• (D) A large permanent vacuole filled with air

Q20. Water moves through a plant by the apoplast pathway. What does this pathway involve?

• (A) Movement through the cytoplasm of living cells via plasmodesmata
• (B) Movement through vacuoles only
• (C) Movement inside xylem vessels after reaching the endodermis
• (D) Movement through cell walls and intercellular spaces, without crossing cell membranes, until the Casparian strip

Q21. Sinks in phloem transport include which examples?

• (A) Growing roots, developing fruits and storage organs that import assimilates
• (B) Mature photosynthetic leaves exporting sucrose
• (C) Xylem vessels carrying water upward
• (D) Stomata releasing water vapour

Q22. After oxygenation in the lungs, blood returns to the left atrium through which vessel?

• (A) Pulmonary artery
• (B) Vena cava
• (C) Hepatic vein
• (D) Pulmonary vein

Q23. Capillaries are adapted for exchange by which features?

• (A) Walls one cell thick, narrow lumens slowing flow, and a very large total surface area
• (B) Thick muscular walls and valves
• (C) Elastic tissue that maintains high pressure
• (D) A wide lumen and rapid blood flow

Q24. Excess tissue fluid that is not reabsorbed into capillaries is returned to the blood by which system?

• (A) The hepatic portal system
• (B) The lymphatic system, draining into veins near the heart
• (C) The pulmonary circulation
• (D) The renal system only

Q25. In fish gills, water flows over lamellae in the opposite direction to blood flow inside them. What advantage does this arrangement give?

• (A) It maintains a diffusion gradient along the whole lamella, maximising oxygen uptake
• (B) Fish ventilate their lungs by rib movements
• (C) Fish use a diaphragm to draw water over the gills
• (D) Fish rely only on diffusion of water through their skin

Q26. In mammals, the trachea is kept open by which structures?

• (A) Smooth muscle rings that contract fully around it
• (B) C-shaped rings of cartilage that prevent collapse while allowing the oesophagus to expand
• (C) Bone plates surrounding the airway
• (D) Alveoli attached to its walls

Q27. Goblet cells in the airways produce mucus. What is the function of this mucus combined with cilia?

• (A) To absorb oxygen into the blood
• (B) To warm inhaled air only
• (C) To trap dust and pathogens, which cilia then move upward toward the throat
• (D) To increase the surface area for gas exchange

Q28. Which pathogen causes malaria, and what type of organism is it?

• (A) A bacterium transmitted by contaminated water
• (B) A protoctist of the genus Plasmodium, transmitted by Anopheles mosquitoes
• (C) A virus transmitted by airborne droplets
• (D) A fungus growing on skin

Q29. Why do people with HIV become vulnerable to opportunistic infections?

• (A) HIV destroys red blood cells, causing anaemia
• (B) HIV blocks all phagocytosis immediately
• (C) HIV destroys helper T cells, weakening both humoral and cell-mediated immunity
• (D) HIV prevents the skin from acting as a barrier

Q30. The best strategy to reduce antibiotic resistance in hospitals includes which combination?

• (A) Prescribing antibiotics for all viral infections as a precaution
• (B) Stopping antibiotic courses as soon as symptoms improve
• (C) Sharing antibiotics between patients to save supplies
• (D) Prescribing antibiotics only when needed, completing courses, and practising strict hygiene

Q31. Clonal selection in B lymphocytes means what?

• (A) All B cells produce the same antibody regardless of antigen
• (B) B cells mutate to create a new antigen
• (C) A B cell with a receptor matching an antigen is selected to divide, producing identical plasma cells and memory cells
• (D) B cells are selected by antibiotics in the blood

Q32. Autoimmune disease occurs when the immune system does what?

• (A) Fails to produce any antibodies
• (B) Produces antibodies only against foreign antigens
• (C) Loses all memory cells after infection
• (D) Mistakenly attacks the body’s own tissues as if they were foreign

Q33. Natural active immunity is acquired by which route?

• (A) Infection with a pathogen, followed by the body’s own immune response and memory cell formation
• (B) Injection of ready-made antibodies
• (C) Vaccination with a weakened pathogen
• (D) Transfer of antibodies across the placenta only

Q34. Glycolysis occurs in the cytoplasm and produces which net yield per glucose molecule?

• (A) 32 ATP and 2 reduced NAD
• (B) 4 ATP, no reduced NAD and 1 pyruvate
• (C) 6 ATP and 6 carbon dioxide
• (D) A net yield of 2 ATP, 2 reduced NAD and 2 pyruvate molecules

Q35. The link reaction converts pyruvate to acetyl coenzyme A. What else is produced in this step?

• (A) Carbon dioxide and reduced NAD
• (B) Oxygen and ATP directly
• (C) Glucose and water
• (D) Lactate and ethanol

Q36. Why does cyanide poisoning rapidly stop aerobic respiration?

• (A) It prevents glycolysis in the cytoplasm
• (B) It inhibits the final cytochrome in the electron transport chain, so electrons cannot be passed to oxygen
• (C) It breaks down all ATP in the cell
• (D) It prevents glucose entering the cell

Q37. Which statement about photosystem I and photosystem II is correct?

• (A) Photosystem II acts first, splitting water and passing electrons via carriers to photosystem I
• (B) Photosystem I acts first and directly splits water
• (C) Only photosystem I is involved in non-cyclic photophosphorylation
• (D) Both photosystems produce glucose directly

Q38. In the Calvin cycle, carbon dioxide is fixed by combining with which molecule, catalysed by which enzyme?

• (A) Glycerate 3-phosphate, catalysed by ATP synthase
• (B) Ribulose bisphosphate, catalysed by rubisco
• (C) Triose phosphate, catalysed by chlorophyll
• (D) Glucose, catalysed by amylase

Q39. At low temperature, photosynthesis rate is limited mainly because of what?

• (A) Stomata close permanently
• (B) Chlorophyll is destroyed
• (C) Enzyme activity in the Calvin cycle is reduced, slowing carbon fixation
• (D) Light absorption stops completely

Q40. Negative feedback is essential in homeostasis because it does what?

• (A) Amplifies any change in the internal environment
• (B) Reverses a change, returning the controlled variable toward its set point
• (C) Prevents any response to external stimuli
• (D) Maintains a variable at a constantly rising level

Q41. Which hormone is released by the posterior pituitary gland to regulate water balance?

• (A) Insulin
• (B) Glucagon
• (C) Antidiuretic hormone
• (D) Thyroxine

Q42. In osmoregulation, a person who drinks a large volume of water will produce urine that is how different, and why?

• (A) Small in volume and concentrated, because ADH rises
• (B) Large in volume and dark, because the kidney cannot process water
• (C) Unchanged, because water intake does not affect ADH
• (D) Large in volume and dilute, because ADH falls and less water is reabsorbed

Q43. Which sequence correctly describes transmission across a synapse?

• (A) Neurotransmitter is released from the postsynaptic membrane into the presynaptic cell
• (B) An action potential jumps directly from one neurone to the next without chemicals
• (C) Neurotransmitter diffuses across the synaptic cleft, binds receptors, and triggers a response in the postsynaptic cell
• (D) Calcium ions flow from the postsynaptic cell into the presynaptic cell

Q44. The resting potential of a neurone is maintained mainly by which mechanism?

• (A) Open sodium channels allowing sodium to flood in
• (B) Closed potassium channels preventing any potassium movement
• (C) Neurotransmitter constantly released at synapses
• (D) Sodium-potassium pumps and differential membrane permeability, keeping the inside negative relative to outside

Q45. Which plant hormone promotes fruit ripening and leaf abscission?

• (A) Ethene
• (B) Auxin only
• (C) Gibberellin only
• (D) Cytokinin only

Q46. A man with blood group AB marries a woman with blood group O. What blood groups are possible in their children?

• (A) AB only
• (B) O only
• (C) AB and O only
• (D) A and B only

Q47. Colour blindness is an X-linked recessive condition. A colour-blind man marries a woman with normal vision whose father was colour-blind. What proportion of their daughters will be colour-blind?

• (A) Half of their daughters
• (B) None, because daughters receive a normal X chromosome from their mother in every case
• (C) All of their daughters
• (D) One quarter of their daughters

Q48. In a monohybrid cross between two heterozygotes, the genotypic ratio in the offspring is which ratio?

• (A) 3:1 dominant to recessive phenotype
• (B) 1 homozygous dominant : 2 heterozygous : 1 homozygous recessive
• (C) 9:3:3:1
• (D) 1:1

Q49. Which definition of a species is most widely used in A-Level biology?

• (A) A group of organisms that can interbreed to produce fertile offspring
• (B) A group of organisms that look identical
• (C) A group of organisms living in the same habitat
• (D) A group of organisms with the same chromosome number only

Q50. Stabilising selection is most likely to occur in which situation?

• (A) A population colonises a completely new environment
• (B) The environment is stable and the average phenotype is already well adapted
• (C) Two different niches favour opposite extremes
• (D) A new predator favours only the largest individuals

Q51. Genetic drift has the greatest effect in which populations?

• (A) Very large populations with random mating
• (B) Populations with high gene flow
• (C) Small populations, where chance events can change allele frequencies markedly
• (D) Populations under strong directional selection only

Q52. Using the Hardy-Weinberg equation, if the frequency of a recessive allele is 0.2, what is the expected frequency of homozygous recessive individuals?

• (A) 0.04
• (B) 0.20
• (C) 0.40
• (D) 0.80

Q53. Which level of biodiversity refers to variation in genes within a species?

• (A) Ecosystem diversity
• (B) Genetic diversity
• (C) Species diversity only
• (D) Habitat diversity only

Q54. Habitat fragmentation threatens species because it does what?

• (A) Increases the total area of habitat available
• (B) Connects populations with corridors
• (C) Isolates small populations, increasing inbreeding and edge effects
• (D) Removes all predators from the area

Q55. Which conservation approach involves protecting a whole ecosystem in a national park?

• (A) Captive breeding in a zoo
• (B) Seed banking
• (C) Botanical garden cultivation
• (D) In situ conservation

Q56. The main ethical argument against keeping endangered animals only in zoos is which concern?

• (A) Zoos are always more expensive than reserves
• (B) Animals cannot breed in captivity at all
• (C) Captive populations lose all genetic diversity immediately
• (D) Ex situ conservation alone cannot preserve natural behaviours, interactions and evolutionary processes

Q57. A vector in genetic engineering is best defined as what?

• (A) A bacterium that produces antibiotics
• (B) An enzyme that cuts DNA
• (C) A carrier DNA molecule, such as a plasmid, used to transfer a gene into a host cell
• (D) A primer used in PCR

Q58. DNA ligase is used in recombinant DNA technology to do what?

• (A) Cut DNA at specific sequences
• (B) Amplify DNA by PCR
• (C) Separate DNA fragments by size
• (D) Join DNA fragments by forming phosphodiester bonds between them

Q59. Which application of genetic technology raises the most direct concern about gene flow to wild relatives?

• (A) Growing herbicide-resistant GM crops near wild relatives that could receive the gene by pollination
• (B) Using PCR in a laboratory to diagnose disease
• (C) Producing insulin in contained bacterial fermenters
• (D) Using DNA profiling for forensic identification

Q60. In PCR, primers are needed because DNA polymerase can only do what?

• (A) Copy DNA without a template, using primers as a guide for the whole genome
• (B) Start synthesis at a free 3-prime hydroxyl group and extend an existing strand
• (C) Denature DNA at high temperature
• (D) Join Okazaki fragments on the lagging strand