AP Biology Practice Test 14 – 60 Questions with Answers (College Board)

Q1. Water has a high heat of vaporisation. How does this benefit a human who sweats on a hot day?

• (A) Sweat raises body temperature quickly
• (B) Evaporation of sweat removes a large amount of heat from the skin
• (C) Water vapour condenses and warms the body
• (D) Sweating prevents all water loss

Q2. A solution has [H⁺] = 1 x 10^-9 M. What is its pH and is it acidic or basic?

• (A) pH 9, basic
• (B) pH 9, acidic
• (C) pH 5, basic
• (D) pH 3, acidic

Q3. Which pair of molecules are isomers?

• (A) Glucose and sucrose, which have the same formula
• (B) Water and carbon dioxide
• (C) Glucose and fructose, which share the formula C₆H₁₂O₆ but differ in structure
• (D) Starch and cellulose, which are identical

Q4. Amino acids are joined by peptide bonds. What is removed when a peptide bond forms?

• (A) A water molecule
• (B) A carbon dioxide molecule
• (C) An oxygen molecule
• (D) A nitrogen atom

Q5. Which carbohydrate is the main energy storage molecule in animals?

• (A) Cellulose
• (B) Chitin
• (C) Starch
• (D) Glycogen

Q6. A protein contains several polypeptide chains. What level of structure describes how these chains are arranged together?

• (A) Primary structure
• (B) Secondary structure
• (C) Tertiary structure
• (D) Quaternary structure

Q7. In DNA, the two strands are antiparallel. What does this mean?

• (A) They have identical sequences
• (B) They run in opposite 5′ to 3′ directions
• (C) They are joined by covalent bonds between bases
• (D) They run in the same direction

Q8. Chitin is a structural polysaccharide found in fungal cell walls and arthropod exoskeletons. What is its monomer?

• (A) Fructose
• (B) A nitrogen-containing derivative of glucose (N-acetylglucosamine)
• (C) Amino acids
• (D) Fatty acids

Q9. Which organelle is the site of lipid synthesis and detoxification in liver cells?

• (A) The smooth endoplasmic reticulum
• (B) The rough endoplasmic reticulum
• (C) The Golgi apparatus
• (D) The ribosome

Q10. A cell takes in large droplets of fat by endocytosis. Which type of endocytosis is most likely?

• (A) Osmosis
• (B) Phagocytosis
• (C) Facilitated diffusion
• (D) Active transport through a pump

Q11. The plasma membrane is selectively permeable. What does this mean?

• (A) It allows all substances through equally
• (B) It allows some substances through but not others
• (C) It blocks all substances
• (D) It only allows water through

Q12. A plant cell in a hypotonic solution gains water. What prevents it from bursting?

• (A) The vacuole pumps water out
• (B) The chloroplasts absorb the extra water
• (C) The cell wall provides mechanical resistance
• (D) The nucleus expands to absorb pressure

Q13. Which component of the cell membrane is responsible for cell recognition and signalling?

• (A) Phospholipid tails in the interior
• (B) Cholesterol buried in the bilayer
• (C) Integral proteins that span the membrane only for transport
• (D) Glycoproteins and glycolipids on the outer surface

Q14. A eukaryotic cell is 20 micrometres across. Which microscope is needed to see its internal organelles in detail?

• (A) A transmission electron microscope
• (B) A light microscope at low power only
• (C) A magnifying glass
• (D) No microscope, because organelles are visible to the eye

Q15. Which process moves vesicles from the Golgi apparatus to the plasma membrane for secretion?

• (A) Endocytosis
• (B) Phagocytosis
• (C) Osmosis
• (D) Exocytosis

Q16. Which statement best describes the role of enzymes in a reaction?

• (A) They increase activation energy to slow the reaction
• (B) They are consumed and must be replaced after each reaction
• (C) They change the equilibrium position of the reaction
• (D) They lower activation energy and speed the reaction without being consumed

Q17. A metabolic pathway is regulated by feedback inhibition. What happens when the end product accumulates?

• (A) It activates the first enzyme in the pathway
• (B) It is converted back to the starting substrate
• (C) It destroys the pathway enzymes
• (D) It binds to an allosteric site on an early enzyme and slows the pathway

Q18. In the light reactions, which photosystem is responsible for splitting water?

• (A) Photosystem I only
• (B) The Calvin cycle
• (C) Photosystem II
• (D) The Krebs cycle

Q19. A C₄ plant fixes carbon dioxide into a four-carbon compound in mesophyll cells, then releases it in bundle-sheath cells. What is the advantage?

• (A) It allows photosynthesis in the dark
• (B) It eliminates the need for water
• (C) It concentrates CO₂ around Rubisco, reducing photorespiration in hot conditions
• (D) It produces more oxygen than C₃ plants

Q20. During aerobic respiration, NADH from glycolysis is shuttled into the mitochondria. What is the main purpose of this?

• (A) To make glucose in the cytoplasm
• (B) To release carbon dioxide
• (C) To synthesise ATP by substrate-level phosphorylation
• (D) To deliver electrons to the electron transport chain for ATP production

Q21. A yeast culture is grown with oxygen and then switched to anaerobic conditions. What change in glucose consumption is expected?

• (A) Glucose consumption falls to zero
• (B) Glucose consumption stays the same
• (C) Glucose consumption rises because fermentation yields far less ATP per glucose
• (D) Glucose is no longer needed

Q22. The proton gradient across the inner mitochondrial membrane stores energy. What happens if the membrane becomes leaky to protons?

• (A) ATP synthesis increases
• (B) ATP synthesis falls because the gradient that drives ATP synthase is lost
• (C) The electron transport chain stops producing NADH
• (D) Glycolysis produces more ATP

Q23. A cell responds to a signal by changing gene expression. Which step in the pathway is most likely to be the slowest?

• (A) Transcription and translation of new proteins
• (B) Binding of the ligand to its receptor
• (C) Activation of a second messenger
• (D) Phosphorylation of a target protein

Q24. In a signal transduction pathway, a protein phosphatase removes phosphate groups from target proteins. What is its role?

• (A) To turn off the signal by reversing phosphorylation
• (B) To amplify the signal by adding phosphates
• (C) To bind the ligand at the receptor
• (D) To synthesise second messengers

Q25. A plant responds to a pathogen attack by producing defensive chemicals throughout the plant. This systemic response is an example of

• (A) long-distance cell communication
• (B) cell division only
• (C) apoptosis in all cells
• (D) photosynthesis

Q26. Which of the following is a correct sequence of events in the cell cycle?

• (A) S, G₁, M, G₂
• (B) M, G₁, G₂, S
• (C) G₂, G₁, S, M
• (D) G₁, S, G₂, M

Q27. A cell is treated with a drug that prevents microtubules from depolymerising, so chromosomes cannot move toward the poles. Which mitotic stage is directly blocked?

• (A) Anaphase, when sister chromatids are pulled to opposite poles
• (B) Prophase, when chromosomes condense and the spindle forms
• (C) Metaphase, when chromosomes align at the cell equator
• (D) Telophase, when nuclear envelopes re-form around the two sets of chromosomes

Q28. A drug that prevents microtubule formation would most directly block which process?

• (A) Separation of chromosomes during mitosis
• (B) DNA replication
• (C) Protein synthesis
• (D) Glycolysis

Q29. In a multicellular organism, cell division is controlled by growth factors. What happens when a cell loses its response to growth factors?

• (A) It always divides faster
• (B) It may stop dividing or divide inappropriately, depending on the mutation
• (C) It always undergoes apoptosis
• (D) It becomes a stem cell

Q30. A pea plant with purple flowers (dominant) is crossed with a white-flowered plant. Half the offspring have white flowers. What is the genotype of the purple parent?

• (A) Homozygous dominant (PP)
• (B) Heterozygous (Pp)
• (C) Homozygous recessive (pp)
• (D) Hemizygous

Q31. Two genes are located on different chromosomes. What is the expected phenotypic ratio in the offspring of AaBb x aabb?

• (A) 9:3:3:1
• (B) 3:1
• (C) 1:2:1
• (D) 1:1:1:1

Q32. A geneticist observes that a trait is passed from father to son and appears in all male descendants. What is the most likely mode of inheritance?

• (A) X-linked recessive
• (B) Y-linked
• (C) Autosomal dominant
• (D) Mitochondrial

Q33. In humans, the ABO blood group system shows codominance between I^A and I^B. What blood type results from genotype I^AI^B?

• (A) Type A
• (B) Type AB
• (C) Type B
• (D) Type O

Q34. A woman with blood type O has a child with blood type AB. What can be concluded about the father?

• (A) He must be type O
• (B) He must be type A
• (C) He must carry both I^A and I^B alleles
• (D) He must be type B

Q35. A cross between two heterozygous parents for a single gene gives 200 offspring. How many are expected to be homozygous recessive?

• (A) 100
• (B) 25
• (C) 50
• (D) 150

Q36. Which statement about linked genes is correct?

• (A) They are always on different chromosomes
• (B) They always assort independently
• (C) They cannot be separated by crossing over
• (D) They are on the same chromosome and tend to be inherited together

Q37. Which molecule carries the genetic information from the nucleus to the ribosome?

• (A) Messenger RNA
• (B) Transfer RNA
• (C) Ribosomal RNA alone
• (D) DNA polymerase

Q38. A DNA fragment is replicated in vitro. Which enzyme is used in PCR to withstand high temperatures?

• (A) DNA ligase
• (B) Helicase
• (C) Taq polymerase
• (D) RNA polymerase

Q39. A mutation deletes three nucleotides from a coding region. What is the most likely effect?

• (A) Loss of one amino acid, with the rest of the protein unchanged
• (B) A frameshift changing all downstream amino acids
• (C) No change in the protein
• (D) A premature stop codon

Q40. In a eukaryotic cell, the 5′ cap and poly-A tail are added to mRNA. What is their main function?

• (A) To code for amino acids
• (B) To splice out introns
• (C) To replicate the DNA
• (D) To protect the mRNA from degradation and aid export and translation

Q41. A gene is regulated by a repressor protein that binds to an operator. When the repressor is bound, what happens?

• (A) Transcription is blocked
• (B) Transcription is increased
• (C) Translation is increased
• (D) DNA replication is blocked

Q42. A researcher wants to determine the sequence of a DNA fragment. Which technique is most appropriate?

• (A) Gel electrophoresis alone
• (B) PCR alone, without sequencing
• (C) DNA sequencing (e.g. Sanger or next-generation sequencing)
• (D) Southern blotting alone

Q43. A plasmid containing a gene for insulin is inserted into bacteria, which then produce human insulin. What is this an example of?

• (A) Natural selection
• (B) Meiosis
• (C) Genetic engineering using recombinant DNA
• (D) Cloning by cell division only

Q44. A point mutation in a gene changes the amino acid from leucine to proline in the middle of an alpha helix. What is the most likely effect on the protein?

• (A) No effect, because all amino acids are identical
• (B) The helix is disrupted, potentially altering protein function
• (C) The protein becomes longer
• (D) The DNA is repaired automatically

Q45. A population of moths has light and dark forms. After industrial soot darkens tree trunks, dark moths become more common. This is an example of

• (A) mutation creating new alleles in response to soot
• (B) genetic drift with no selection
• (C) natural selection acting on existing variation
• (D) artificial selection by humans

Q46. In a population in Hardy-Weinberg equilibrium, the frequency of the dominant allele is 0.7. What is the frequency of carriers (heterozygotes)?

• (A) 0.49
• (B) 0.09
• (C) 0.70
• (D) 0.42

Q47. Which situation would most increase the chance of speciation?

• (A) High gene flow between populations
• (B) A very large, well-mixed population
• (C) Geographic isolation of a population in a new environment
• (D) Random mating with no selection

Q48. A trait that is no longer used, such as the pelvic bones in whales, is called

• (A) homologous
• (B) analogous
• (C) adaptive
• (D) vestigial

Q49. Which of the following is a prezygotic reproductive barrier?

• (A) Hybrid offspring that are sterile
• (B) Different mating seasons preventing fertilisation
• (C) Hybrid offspring that die before reproducing
• (D) A zygote that fails to develop

Q50. A scientist compares the amino-acid sequence of haemoglobin in several species. Species with the most similar sequences are most likely to be

• (A) most closely related evolutionarily
• (B) most distantly related
• (C) unrelated to each other
• (D) the same species

Q51. The first cells on Earth were most likely

• (A) eukaryotic, photosynthetic autotrophs
• (B) multicellular animals
• (C) viruses with DNA genomes
• (D) prokaryotic, anaerobic heterotrophs

Q52. A population of bacteria is exposed to an antibiotic. A few resistant cells survive and reproduce. What has happened?

• (A) The antibiotic caused mutations for resistance in every cell
• (B) The bacteria learned to resist the antibiotic
• (C) Natural selection has favoured resistant variants already present in the population
• (D) The antibiotic created a new species immediately

Q53. A plant closes its stomata during a drought. What is the main benefit and the main cost?

• (A) Increased water loss and increased photosynthesis
• (B) Reduced water loss and increased CO₂ uptake
• (C) Reduced water loss, but reduced CO₂ uptake for photosynthesis
• (D) No benefit and no cost

Q54. A food web includes grass, rabbits, foxes and eagles. If rabbits are removed, what is the most likely immediate effect?

• (A) Eagles increase in number immediately
• (B) Grass biomass decreases
• (C) Foxes switch to eating eagles
• (D) Foxes lose a food source and grass biomass increases

Q55. A population of bacteria doubles every 20 minutes. Starting from 100 cells, how many cells are there after 1 hour?

• (A) 300 cells
• (B) 800 cells
• (C) 400 cells
• (D) 1,600 cells

Q56. Which factor is density-independent?

• (A) A hurricane destroying nests regardless of population size
• (B) Competition for nesting sites
• (C) Spread of disease in a crowded population
• (D) Predation that increases with prey density

Q57. In primary succession, the first organisms to colonise bare rock are usually

• (A) large trees
• (B) lichens and mosses
• (C) shrubs
• (D) mammals

Q58. Which biome has the highest net primary productivity per unit area?

• (A) Desert
• (B) Tropical rainforest
• (C) Tundra
• (D) Open ocean per unit area

Q59. A lake is polluted with heavy metals that accumulate in fish. Top predators have the highest concentrations. This is an example of

• (A) biomagnification
• (B) bioaccumulation only in producers
• (C) eutrophication
• (D) competitive exclusion

Q60. Which human activity most directly contributes to the loss of biodiversity in rainforests?

• (A) Establishing nature reserves
• (B) Reducing fossil fuel use
• (C) Deforestation for agriculture and logging
• (D) Replanting native trees