A-Level Biology Practice Test 6 – 60 Questions with Answers (Cambridge 9700)
This test covers the full A-Level syllabus, from cell structure to genetic technology, at the depth expected in Paper 1 and Paper 2 questions. Use it to check recall and application before revising your weakest topics.
Cell structure
Q1. Which organelle is the site of oxidative phosphorylation in a eukaryotic cell?
- (A) Mitochondrion
- (B) Golgi body
- (C) Ribosome
- (D) Lysosome
Show Answer
Answer: A – The inner mitochondrial membrane carries the electron transport chain and ATP synthase.
Q2. Which feature is present in a prokaryotic cell but absent from a typical eukaryotic cell?
- (A) A nucleus enclosed by a double membrane
- (B) Circular DNA free in the cytoplasm
- (C) Membrane-bound mitochondria
- (D) A cytoskeleton of protein fibres
Show Answer
Answer: B – Prokaryotes have circular DNA not enclosed in a nucleus, and 70S ribosomes.
Q3. Which structure is responsible for modifying, packaging and secreting proteins?
- (A) Rough endoplasmic reticulum
- (B) Smooth endoplasmic reticulum
- (C) Golgi body
- (D) Nucleolus
Show Answer
Answer: C – Proteins from the rough endoplasmic reticulum are modified and packaged in Golgi vesicles.
Biological molecules
Q4. Which bond joins two amino acids in a polypeptide?
- (A) Hydrogen bond
- (B) Ionic bond
- (C) Glycosidic bond
- (D) Peptide bond
Show Answer
Answer: D – A condensation reaction between amino acids forms a peptide bond and releases water.
Q5. Which polysaccharide is branched and used for energy storage in animals?
- (A) Glycogen
- (B) Cellulose
- (C) Starch in amylopectin form only
- (D) Chitin
Show Answer
Answer: A – Glycogen is highly branched, so glucose can be released rapidly from many ends.
Q6. A solution gives a purple colour in the biuret test. What does this indicate?
- (A) Reducing sugar present
- (B) Protein present
- (C) Starch present
- (D) Lipid present
Show Answer
Answer: B – The biuret reagent turns purple in the presence of peptide bonds.
Enzymes
Q7. A non-competitive inhibitor reduces the rate of an enzyme-catalysed reaction. What is its effect on Vmax and Km?
- (A) Vmax increases, Km unchanged
- (B) Vmax unchanged, Km increases
- (C) Vmax decreases, Km unchanged
- (D) Vmax unchanged, Km decreases
Show Answer
Answer: C – A non-competitive inhibitor binds away from the active site, so fewer enzyme molecules work, lowering Vmax without changing Km.
Q8. Why does increasing substrate concentration eventually stop increasing reaction rate?
- (A) The enzyme is denatured
- (B) The product inhibits the substrate
- (C) The pH changes sharply
- (D) All active sites become saturated
Show Answer
Answer: D – At saturation every active site is occupied, so rate is limited by the enzyme concentration.
Q9. Which statement best describes the induced-fit model?
- (A) The substrate changes the shape of the active site on binding
- (B) The active site is rigid and exactly matches the substrate
- (C) The enzyme is consumed during the reaction
- (D) The product binds more tightly than the substrate
Show Answer
Answer: A – Binding induces a conformational change that improves the fit and stresses substrate bonds.
Cell membranes and transport
Q10. Which process moves ions against a concentration gradient using ATP?
- (A) Simple diffusion
- (B) Active transport
- (C) Facilitated diffusion
- (D) Osmosis
Show Answer
Answer: B – Active transport uses ATP to pump solutes against their concentration gradient via carrier proteins.
Q11. In the fluid mosaic model, what is the main function of cholesterol in animal cell membranes?
- (A) To form channels for water
- (B) To synthesise ATP
- (C) To regulate membrane fluidity
- (D) To bind to antigens
Show Answer
Answer: C – Cholesterol restricts phospholipid movement at high temperature and prevents packing at low temperature.
Q12. A red blood cell is placed in distilled water. What happens?
- (A) It shrinks by plasmolysis
- (B) It remains unchanged
- (C) It loses water by active transport
- (D) It swells and may burst
Show Answer
Answer: D – Water enters by osmosis down a water potential gradient, and the cell has no wall to resist bursting.
The mitotic cell cycle
Q13. During which phase of mitosis do sister chromatids separate?
- (A) Anaphase
- (B) Prophase
- (C) Metaphase
- (D) Telophase
Show Answer
Answer: A – Spindle fibres shorten and pull sister chromatids to opposite poles in anaphase.
Q14. What happens while the spindle assembly checkpoint remains unsatisfied during mitosis?
- (A) DNA replication speeds up in all cells
- (B) Anaphase is delayed until every chromosome is attached to spindle fibres
- (C) The chromosome number doubles
- (D) Cytokinesis is triggered directly
Show Answer
Answer: B – The spindle checkpoint prevents anaphase until all chromosomes are correctly attached, avoiding unequal chromosome distribution.
Q15. Which event occurs during interphase, before mitosis begins?
- (A) Chromosomes line up on the equator
- (B) The nuclear envelope breaks down
- (C) DNA replicates
- (D) Chromatids move to opposite poles
Show Answer
Answer: C – DNA replication in S phase ensures each daughter cell receives a full copy of the genome.
Nucleic acids and protein synthesis
Q16. Which base pairing occurs in DNA but not in RNA?
- (A) Adenine with uracil
- (B) Guanine with cytosine
- (C) Cytosine with guanine
- (D) Adenine with thymine
Show Answer
Answer: D – DNA contains thymine, whereas RNA contains uracil in its place.
Q17. During translation, what is the role of tRNA?
- (A) It carries a specific amino acid to the ribosome
- (B) It copies DNA into mRNA
- (C) It unwinds the DNA double helix
- (D) It splices introns from pre-mRNA
Show Answer
Answer: A – Each tRNA anticodon matches an mRNA codon and delivers the corresponding amino acid.
Q18. Which feature of the genetic code means that several codons can code for the same amino acid?
- (A) It is universal
- (B) It is degenerate
- (C) It is non-overlapping
- (D) It has stop codons
Show Answer
Answer: B – Degeneracy means most amino acids are coded by more than one codon.
Transport in plants
Q19. Which tissue transports sucrose from source to sink in a plant?
- (A) Xylem vessels
- (B) Cambium
- (C) Phloem sieve tubes
- (D) Epidermis
Show Answer
Answer: C – Phloem sieve tubes, supported by companion cells, carry assimilates by mass flow.
Q20. What drives the movement of water up the xylem in the cohesion-tension theory?
- (A) Active pumping by root cells
- (B) Osmosis into phloem
- (C) Diffusion through stomata only
- (D) Transpiration pull from leaves
Show Answer
Answer: D – Water loss from leaves creates tension that pulls a continuous water column upward.
Q21. Which adaptation reduces water loss from a xerophytic leaf?
- (A) A thick waxy cuticle and sunken stomata
- (B) Large, thin leaves with many stomata
- (C) A reduced cuticle and open stomata
- (D) Stomata only on the upper surface
Show Answer
Answer: A – A thick cuticle and sunken stomata trap humid air and reduce the diffusion gradient for water vapour.
Transport in mammals
Q22. Blood leaving the left ventricle during systole enters which vessel first?
- (A) The pulmonary artery
- (B) The aorta
- (C) The vena cava
- (D) The pulmonary vein
Show Answer
Answer: B – The aorta carries oxygenated blood from the left ventricle to the body, while the pulmonary artery leaves the right ventricle.
Q23. Why does fetal haemoglobin have a higher affinity for oxygen than adult haemoglobin?
- (A) To release oxygen more easily in the lungs
- (B) To carry more carbon dioxide
- (C) To take up oxygen from maternal blood across the placenta
- (D) To resist the Bohr effect
Show Answer
Answer: C – Its dissociation curve lies to the left, so it loads oxygen at the lower partial pressures in the placenta.
Q24. What happens to the atrioventricular valves during ventricular systole?
- (A) They open to let blood into the atria
- (B) They open to let blood into the arteries
- (C) They remain open throughout
- (D) They close to prevent backflow into the atria
Show Answer
Answer: D – Rising ventricular pressure closes the valves, and their tendons prevent them inverting.
Gas exchange
Q25. Which feature of alveoli best increases the rate of gas exchange?
- (A) A large total surface area and thin walls
- (B) A thick wall with a rich mucus layer
- (C) A small surface area with slow blood flow
- (D) A single large air sac with no capillaries
Show Answer
Answer: A – Millions of thin-walled alveoli give a huge surface area and a short diffusion distance.
Q26. In fish, why does water flow over the gills in the opposite direction to blood flow?
- (A) To reduce the surface area available
- (B) To maintain a diffusion gradient along the whole lamella
- (C) To slow oxygen uptake
- (D) To prevent water entering the blood
Show Answer
Answer: B – Countercurrent flow keeps blood always meeting water with a higher oxygen concentration.
Q27. Which organism exchanges gases through spiracles and tracheae?
- (A) A fish
- (B) A mammal
- (C) An insect
- (D) A flatworm
Show Answer
Answer: C – Insects take air in through spiracles into a branching tracheal system ending in tracheoles.
Infectious diseases
Q28. Why does cholera cause rapid dehydration even though Vibrio cholerae remains in the gut lumen?
- (A) The bacterium invades red blood cells and destroys them
- (B) A virus carried by the bacterium blocks kidney function
- (C) Fungal spores in the gut absorb water from the blood
- (D) A toxin released by the bacterium causes chloride ions and water to be secreted into the gut
Show Answer
Answer: D – The cholera toxin overactivates ion channels in gut cells, so large volumes of water follow ions into the lumen.
Q29. Why are antibiotics ineffective against HIV?
- (A) Antibiotics target bacterial structures, not viruses
- (B) HIV has a cell wall that blocks antibiotics
- (C) HIV replicates too slowly for antibiotics
- (D) Antibiotics cannot enter human cells
Show Answer
Answer: A – Viruses lack bacterial targets such as peptidoglycan walls and 70S ribosomes.
Q30. Which statement about tuberculosis is correct?
- (A) It is caused by a virus that attacks the liver
- (B) It is caused by a bacterium spread in droplets from coughing
- (C) It is caused by a fungus spread through food
- (D) It is caused by a protoctist carried by mosquitoes
Show Answer
Answer: B – Mycobacterium tuberculosis infects the lungs and spreads in airborne droplets.
Immunity
Q31. Which cells produce antibodies in a specific immune response?
- (A) Phagocytes
- (B) Helper T cells only
- (C) Plasma cells derived from B lymphocytes
- (D) Red blood cells
Show Answer
Answer: C – Clonal expansion of B cells produces plasma cells that secrete specific antibodies.
Q32. What is the role of memory cells after a first infection?
- (A) They destroy pathogens by phagocytosis immediately
- (B) They produce histamine at the infection site
- (C) They prevent antibodies from being made
- (D) They allow a faster, stronger secondary response
Show Answer
Answer: D – Memory cells persist and divide rapidly on re-exposure to the same antigen.
Q33. Which process describes how phagocytes destroy a pathogen?
- (A) They engulf it and digest it with lysosomal enzymes
- (B) They release antibodies into the blood
- (C) They present it directly to plasma cells
- (D) They block its receptors with complement proteins
Show Answer
Answer: A – The phagocyte forms a phagosome, which fuses with lysosomes containing hydrolytic enzymes.
Energy and respiration
Q34. Where does the link reaction occur, and what does it produce?
- (A) In the cytoplasm, producing pyruvate
- (B) In the mitochondrial matrix, producing acetyl CoA and carbon dioxide
- (C) On the cristae, producing water
- (D) In the chloroplast stroma, producing glucose
Show Answer
Answer: B – Pyruvate is decarboxylated and oxidised to acetyl CoA, releasing carbon dioxide and reduced NAD.
Q35. How is most ATP made in aerobic respiration?
- (A) By substrate-level phosphorylation in glycolysis only
- (B) By photophosphorylation in the chloroplast
- (C) By chemiosmosis using a proton gradient across the inner mitochondrial membrane
- (D) By direct transfer from glucose to ADP
Show Answer
Answer: C – Protons pumped into the intermembrane space flow back through ATP synthase, driving ATP formation.
Q36. What is the respiratory quotient for a substrate that is pure carbohydrate?
- (A) 0.7
- (B) 0.8
- (C) 1.3
- (D) 1.0
Show Answer
Answer: D – Carbohydrate oxidation produces equal volumes of carbon dioxide and oxygen consumed, so RQ equals 1.0.
Photosynthesis
Q37. Which products of the light-dependent reactions are used in the Calvin cycle?
- (A) ATP and reduced NADP
- (B) Oxygen and water
- (C) Glucose and carbon dioxide
- (D) ADP and NADP only
Show Answer
Answer: A – ATP supplies energy and reduced NADP supplies hydrogen for carbon fixation and reduction.
Q38. In the Calvin cycle, what is the first stable product of carbon fixation?
- (A) Ribulose bisphosphate
- (B) Glycerate 3-phosphate
- (C) Triose phosphate
- (D) Glucose
Show Answer
Answer: B – Rubisco fixes carbon dioxide onto ribulose bisphosphate, forming an unstable intermediate that splits into glycerate 3-phosphate.
Q39. At very high light intensity, what is most likely to limit photosynthesis in a well-watered plant?
- (A) Light intensity itself
- (B) Chlorophyll concentration alone
- (C) Carbon dioxide concentration
- (D) Stomatal closure from darkness
Show Answer
Answer: C – Once light is saturating, carbon dioxide supply limits the rate of the Calvin cycle.
Homeostasis
Q40. Which hormone increases water reabsorption in the collecting duct?
- (A) Insulin
- (B) Glucagon
- (C) Adrenaline
- (D) ADH
Show Answer
Answer: D – ADH inserts aquaporins into collecting duct cells, increasing water permeability.
Q41. During ultrafiltration in the kidney, what forces fluid out of the glomerulus?
- (A) High hydrostatic pressure in glomerular capillaries
- (B) Active transport of glucose
- (C) Osmosis into the Bowman’s capsule
- (D) Secretion by podocytes
Show Answer
Answer: A – The afferent arteriole is wider than the efferent arteriole, creating high pressure that forces small molecules through the filtration membrane.
Q42. In negative feedback control of blood glucose, what happens when blood glucose rises?
- (A) Glucagon secretion increases
- (B) Insulin secretion increases and liver takes up glucose
- (C) Insulin secretion falls and glycogen breaks down
- (D) ADH secretion increases
Show Answer
Answer: B – Beta cells release insulin, which increases glucose uptake and glycogenesis, restoring the set point.
Control and coordination
Q43. Which type of neurone carries impulses from a receptor to the central nervous system?
- (A) Motor neurone
- (B) Relay neurone
- (C) Sensory neurone
- (D) Effector neurone
Show Answer
Answer: C – Sensory neurones have a long dendron carrying impulses toward the central nervous system.
Q44. After acetylcholine has triggered depolarisation at a cholinergic synapse, how is the signal switched off so the postsynaptic cell can respond again?
- (A) Sodium channels close permanently
- (B) Potassium ions are actively pumped out only
- (C) Acetylcholine is stored in vesicles in the postsynaptic cell
- (D) Acetylcholine is hydrolysed by acetylcholinesterase in the synaptic cleft into acetate and choline
Show Answer
Answer: D – Hydrolysis removes acetylcholine from receptors, ending depolarisation so the synapse can transmit a new impulse.
Q45. Which plant hormone promotes cell elongation in shoots and phototropism?
- (A) Auxin
- (B) Abscisic acid
- (C) Cytokinin
- (D) Ethene
Show Answer
Answer: A – Auxin accumulates on the shaded side of a shoot, causing faster elongation and bending toward light.
Inheritance
Q46. In a monohybrid cross between two heterozygotes, what is the expected phenotypic ratio?
- (A) 1:2:1
- (B) 3:1
- (C) 9:3:3:1
- (D) 1:1
Show Answer
Answer: B – Three quarters show the dominant phenotype and one quarter the recessive phenotype.
Q47. A gene has alleles A and a with frequencies p and q. Under Hardy-Weinberg equilibrium, what is the frequency of heterozygotes?
- (A) p squared
- (B) q squared
- (C) 2pq
- (D) p plus q
Show Answer
Answer: C – The Hardy-Weinberg equation p squared plus 2pq plus q squared equals 1 gives heterozygote frequency as 2pq.
Q48. Why do linked genes not show the expected 9:3:3:1 ratio in a dihybrid cross?
- (A) They show codominance
- (B) They are on different chromosomes
- (C) They are always lethal in combination
- (D) They are on the same chromosome and tend to be inherited together
Show Answer
Answer: D – Linked genes stay together unless crossing over separates them, so parental combinations are over-represented.
Q49. In a dihybrid cross, a 9:7 phenotypic ratio is observed. What interaction does this show?
- (A) Recessive epistasis
- (B) Codominance
- (C) Multiple alleles
- (D) Sex linkage
Show Answer
Answer: A – In recessive epistasis, a homozygous recessive genotype at one locus masks the effect of another locus, giving a 9:7 ratio.
Selection and evolution
Q50. Which type of selection favours individuals at both extremes of a trait?
- (A) Stabilising selection
- (B) Disruptive selection
- (C) Directional selection
- (D) Artificial selection only
Show Answer
Answer: B – Disruptive selection acts against intermediate phenotypes and can split a population.
Q51. What is the main requirement for allopatric speciation?
- (A) A sudden doubling of chromosome number only
- (B) Artificial selection by humans
- (C) Reproductive isolation caused by geographical separation
- (D) Identical selection pressures in both groups
Show Answer
Answer: C – Geographical barriers prevent gene flow, so separated populations diverge genetically.
Q52. Antibiotic resistance in bacteria spreads mainly because resistant bacteria are selected and then pass resistance genes on. Which process can transfer resistance between bacteria directly?
- (A) Mitosis only
- (B) Meiosis
- (C) Binary fission of viruses
- (D) Conjugation
Show Answer
Answer: D – Conjugation transfers plasmids carrying resistance genes from one bacterium to another.
Q53. Which evidence best supports evolution by natural selection in peppered moths?
- (A) Dark moths increased where soot darkened tree bark
- (B) Moths changed colour within their lifetime by choice
- (C) Light moths were eaten only in clean areas
- (D) Moth populations never changed over time
Show Answer
Answer: A – Camouflaged dark moths survived predation better in polluted areas, increasing their frequency.
Classification, biodiversity and conservation
Q54. In the taxonomic hierarchy, which rank is immediately above genus?
- (A) Species
- (B) Family
- (C) Order
- (D) Kingdom
Show Answer
Answer: B – The hierarchy runs species, genus, family, order, class, phylum, kingdom, domain.
Q55. A high Simpson’s index of diversity (D) indicates what about a community?
- (A) Low species richness and dominance by one species
- (B) Only one species present
- (C) High species richness and even abundance
- (D) No genetic diversity within species
Show Answer
Answer: C – Simpson’s index accounts for both richness and evenness, so high values mean a diverse, even community.
Q56. Which conservation method keeps a species in its natural habitat?
- (A) Captive breeding in a zoo
- (B) Seed banks
- (C) Frozen sperm banks
- (D) A protected nature reserve
Show Answer
Answer: D – In situ conservation, such as a reserve, protects species and their habitat together.
Q57. Why is molecular evidence now used alongside morphology in classification?
- (A) DNA sequences reveal evolutionary relationships that appearance can hide
- (B) Morphology is never useful
- (C) DNA replaces the need for species names
- (D) All organisms have identical DNA
Show Answer
Answer: A – Similar DNA sequences indicate common ancestry, even when convergent evolution produces similar shapes.
Genetic technology
Q58. In PCR, what is the role of Taq polymerase?
- (A) It cuts DNA at specific sequences
- (B) It synthesises new DNA strands at high temperature
- (C) It separates DNA fragments by size
- (D) It inserts DNA into plasmids
Show Answer
Answer: B – Taq polymerase from a thermophilic bacterium remains stable during the denaturation cycles of PCR.
Q59. In gel electrophoresis, one DNA sample produces bands close to the wells while another produces bands near the far end of the gel. What does this indicate about the two samples?
- (A) The sample near the wells carries a positive charge
- (B) The sample near the far end was not cut by restriction enzymes
- (C) The sample near the wells contains larger fragments than the sample near the far end
- (D) The sample near the far end contains more DNA in total
Show Answer
Answer: C – Larger fragments move more slowly through the gel matrix, so they remain closer to the wells than smaller fragments.
Q60. Which step is essential to make recombinant DNA using a plasmid vector?
- (A) Heating DNA to denature it only
- (B) Running the DNA on a gel only
- (C) Amplifying the DNA by PCR only
- (D) Cutting both plasmid and target DNA with the same restriction enzyme
Show Answer
Answer: D – Using the same restriction enzyme creates complementary sticky ends that can be joined by ligase.
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