Skip to main content
Sign in Create a free account
Varsity Tutors
Sign in Sign up

Practice Test 33 - AP Biology

20 questions. Answer them in any order, then submit to see your score and every explanation.

  1. A student models DNA replication at a single replication fork. The parental strands are antiparallel, and DNA polymerase can add nucleotides only to a free 3′ OH, so synthesis proceeds 5′→3′ on both new strands. One strand is made continuously, while the other is made discontinuously as short DNA fragments initiated repeatedly. The student introduces a compound that prevents synthesis of RNA primers but does not affect DNA polymerase's ability to extend from an existing 3′ end. Which outcome is most likely at the replication fork?
  2. In a synchronized cell population, a pulse of a phosphatase inhibitor is applied during late G2. The inhibitor prevents removal of inhibitory phosphates from Cdk1 but does not affect cyclin binding. After the pulse is removed, the phosphatase resumes activity. Cells are monitored for timing of mitotic entry. Which observation is most likely compared with untreated controls?
  3. If two plants that are heterozygous for both traits are crossed, what fraction of the offspring is expected to be tall with white flowers?
  4. An enzyme-catalyzed reaction is measured at 20°C and 60°C with identical substrate concentration. The rate increases from 12 to 30 units at 40°C, then drops to 2 units at 60°C. Which outcome is most likely at 60°C at the molecular level?
  5. Two beakers contain nonpenetrating solute solutions: Beaker 1 is 0.20 M and Beaker 2 is 0.50 M. Identical cells have an internal solute concentration of 0.35 M and membranes permeable to water but not solute. Cells are placed into each beaker and observed for 5 minutes; external concentrations stay constant. Which outcome is most likely for cell volume in Beaker 1 compared with Beaker 2?
  6. A student calculates surface area and volume for two cube-shaped cells. Cell GG has side length 2 units; Cell HH has side length 4 units. Both have identical membrane permeability and rely on diffusion for potassium ion exchange. Potassium use occurs at the same rate per unit volume. Cell HH shows slower potassium uptake per unit volume than Cell GG. Which explanation best accounts for the slower uptake per unit volume in Cell HH?
  7. A bacterial capsule contains a polysaccharide made of repeating units of N-acetylglucosamine and N-acetylmuramic acid, many of which carry carboxyl groups that are deprotonated at neutral pH. In water, the polymer chains repel each other and spread out, trapping large amounts of water around the cells and producing a slippery, hydrated layer. Which property of this carbohydrate polymer best explains its strong water retention?
  8. A flowering plant population has petal length controlled by multiple genes. Pollinator visits are highest to flowers with very short petals and very long petals, and those plants set about twice as many seeds as plants with intermediate petal length. After 12 generations, the distribution of petal lengths becomes more clustered near the two extremes, and intermediate lengths become less common. Population size is large and stable, with no evidence of migration. Which pattern best illustrates the selection acting on petal length?
  9. In a diploid cell with 2n=62n=6, all three homologous pairs align at metaphase I. During anaphase I, homologous chromosomes separate to opposite poles while sister chromatids remain joined at their centromeres. Cytokinesis produces two cells that each contain three chromosomes, each still composed of two sister chromatids. The cells then enter meiosis II without DNA replication. At anaphase II, sister chromatids separate and move to opposite poles. Which outcome is most likely in the gametes produced at the end of meiosis II?
  10. A lab measures CDK activity using phosphorylation of a peptide substrate. In control cells, cyclin B–CDK1 activity is high in metaphase and then drops after APC/C activation. In a mutant, securin is present but cannot bind separase. APC/C activation and cyclin B degradation still occur normally. Which prediction is most consistent with the mutant's signaling state during metaphase-to-anaphase transition?
  11. In yeast cells, ligand P binds a plasma membrane receptor. Within 30 seconds, a specific cytosolic protein becomes phosphorylated. When cells are treated with a kinase inhibitor that targets the receptor-associated kinase, P still binds the receptor, but the cytosolic protein is not phosphorylated. Which of the following best explains the earliest step connecting receptor binding to protein phosphorylation?
  12. A student observes vesicles moving from the Golgi apparatus toward the plasma membrane in an animal cell. When ATP levels are experimentally lowered, vesicle movement slows dramatically, although diffusion of small molecules in the cytosol appears unchanged. Microscopy shows many vesicles aligned along filamentous tracks extending from the cell center. Which feature best explains the ATP-dependent vesicle movement observed?
  13. A student hydrolyzes an unknown polymer and obtains many identical monomers, each with a central carbon bonded to an amino group, a carboxyl group, a hydrogen, and the same R group. The original polymer's backbone contained repeating –N–C–C– units, consistent with covalent bonds formed by dehydration between amino and carboxyl groups. Changes in solution pH alter ionic interactions among side chains and can change the polymer's shape. Which statement best describes the unknown polymer's macromolecule category?
  14. Lactase is incubated with lactose at constant pH. At 10°C the reaction rate is low; at 30°C it increases; at 50°C it drops sharply. Which outcome is most likely at 50°C?
  15. In a coral reef, cleaner wrasse remove ectoparasites from larger client fish at cleaning stations. Observations over several weeks show that client fish visit stations and then display fewer visible parasites. When cleaner wrasse are experimentally excluded from a section of reef, client fish in that section show increased parasite loads and spend less time feeding. Cleaner wrasse feed primarily on the parasites they remove. Which interaction best describes the relationship between cleaner wrasse and client fish?
  16. A membrane is composed of a phospholipid bilayer with a hydrophobic interior. Two solutes are placed on one side: benzoic acid in its uncharged form (C6H5COOH; weak acid, uncharged) and benzoate (C6H5COO−; negatively charged). No transport proteins are present, so crossing requires partitioning into the lipid core. Although both forms have similar size, the charged form remains strongly hydrated and interacts poorly with the nonpolar interior. The uncharged form has reduced electrostatic interactions with water and can enter the bilayer more readily by diffusion.
  17. DNA replication uses complementary base pairing and requires short RNA primers that provide a free 3′-OH for DNA polymerase to extend. A drug prevents primase from synthesizing RNA primers but does not disrupt helicase activity. Which outcome is most likely at replication origins?
  18. Two spherical animal cells are placed in the same isotonic solution with equal concentrations of glucose outside. Cell X has radius 5 μm5\,\mu m; Cell Y has radius 15 μm15\,\mu m. Both have the same membrane composition and the same number of glucose transporters per μm2\mu m^2 of membrane. Glucose enters by facilitated diffusion, and the cells consume glucose at similar rates per unit cytoplasmic volume. After 2 minutes, Cell Y shows a smaller increase in intracellular glucose concentration than Cell X. Which explanation best accounts for the difference in glucose accumulation?
  19. A student models semiconservative replication using a short DNA duplex. One parental strand has the sequence 5′-A G T C C A-3′. During replication, the strands separate and DNA polymerase synthesizes a complementary strand by adding nucleotides to the 3′ end according to base-pairing rules. Assuming accurate replication at this region, which sequence is most likely found on the newly synthesized strand paired to the given parental strand?
  20. A cell enters mitosis with duplicated chromosomes (each chromosome has two sister chromatids). During prometaphase, spindle microtubules attach to kinetochores. A researcher uses a laser to sever microtubules connected to one chromosome, leaving both kinetochores unattached while other chromosomes remain properly attached. The spindle checkpoint monitors unattached kinetochores before allowing anaphase. Which outcome is most likely while the severed chromosome remains unattached?

Practice tests