AP Biology Question Bank & Worked Answers

Original, AI-authored English practice with worked guidance. Selected topics only; independent teacher review is pending. This is not a complete syllabus, official past-paper collection or predicted exam score. SubjectScout is not affiliated with or endorsed by College Board. SAT practice is not a full adaptive test; AP practice does not simulate an entire exam.

16 original questions across 8 selected topic areas. No account or payment required to practise.

Question 1 · Unit 1: Chemistry of Life · foundation

Which property of water helps explain its cohesion?A. Covalent bonds form between separate water molecules.B. Hydrogen bonds form between neighboring water molecules.C. Water molecules have no partial charges.D. Water molecules cannot interact with one another.

Question 2 · Unit 2: Cells · foundation

Identical animal cells with water-permeable membranes are placed in a solution with a lower concentration of nonpenetrating solutes than their cytoplasm. Assume equal temperature and pressure and no additional penetrating solutes. Which initial net change is expected?A. Water leaves and cells shrink.B. No water moves across the membrane.C. Water enters and cells swell.D. Solutes must enter through the lipid bilayer.

Question 3 · Unit 3: Cellular Energetics · foundation

An enzyme is heated well above its normal working temperature. Its activity drops sharply. Which explanation best accounts for this decrease?A. The enzyme is used up as a reactant.B. The substrate must have become an enzyme.C. The enzyme's amino acid sequence necessarily reverses.D. Heat disrupts interactions maintaining the enzyme's functional shape.

Question 4 · Unit 4: Cell Communication and Cell Cycle · foundation

A signaling molecule binds a membrane receptor, which activates several intracellular proteins in sequence. What is this sequence called?A. Signal transductionB. DNA replicationC. TranslationD. Independent assortment

Question 5 · Unit 5: Heredity · foundation

For a single gene with complete dominance, two heterozygous individuals (Aa x Aa) are crossed. Assuming equal segregation and no viability differences, what is the probability an offspring is aa?A. 0B. 1/4C. 1/2D. 3/4

Question 6 · Unit 6: Gene Expression and Regulation · foundation

A segment of the coding DNA strand has sequence 5'-ATG GAA-3'. What is the corresponding mRNA segment before processing?A. 5'-UAC CUU-3'B. 5'-AUG GAA-3'C. 5'-ATG GAA-3'D. 5'-GAA AUG-3'

Question 7 · Unit 7: Natural Selection · foundation

An antibiotic kills susceptible bacteria, while bacteria carrying an existing resistance allele survive and reproduce. Which explanation best describes the resulting population change?A. Every bacterium chooses to become resistant.B. The antibiotic creates precisely the mutation each bacterium needs.C. Selection increases the frequency of an existing heritable resistance allele.D. The resistance allele must disappear in the next generation.

Question 8 · Unit 8: Ecology · foundation

A food chain transfers 10% of the energy at each trophic level to the next. If producers contain 20,000 kJ, how much reaches secondary consumers?A. 20 kJB. 200 kJC. 2,000 kJD. 18,000 kJ

Question 9 · Unit 1: Chemistry of Life · standard

Two proteins have identical amino acid sequences but are placed in solutions with different pH values. Their activities differ. Which explanation is most plausible?A. pH changes the genetic code in every cell.B. Different pH can change side-chain charges and protein folding.C. Identical sequences guarantee identical shape in all conditions.D. Every pH change breaks all peptide bonds.

Question 10 · Unit 2: Cells · challenge

A spherical cell doubles its radius without changing shape. What happens to its surface-area-to-volume ratio?A. It doubles.B. It stays constant.C. It halves.D. It becomes four times larger.

Question 11 · Unit 3: Cellular Energetics · challenge

An inhibitor binds reversibly to an enzyme's active site and competes with its substrate. Under a simple competitive-inhibition model with fixed enzyme and inhibitor concentrations and otherwise unchanged conditions, which change can reduce the inhibitor's effect?A. Increase substrate concentration sufficiently.B. Remove every substrate molecule.C. Destroy the active site.D. Lower enzyme concentration to zero.

Question 12 · Unit 4: Cell Communication and Cell Cycle · standard

A cell has unrepaired DNA damage before DNA replication. Which response best helps prevent propagation of the damage?A. Bypass all checkpoints.B. Activate a checkpoint that delays cell-cycle progression while repair occurs.C. Immediately separate sister chromatids.D. Eliminate every DNA repair enzyme.

Question 13 · Unit 5: Heredity · challenge

An individual heterozygous at two unlinked genes, AaBb, is test-crossed with aabb. With independent assortment and no viability differences, what fraction of offspring is expected to be Aabb?A. 1/16B. 1/4C. 1/2D. 3/4

Question 14 · Unit 6: Gene Expression and Regulation · standard

A substitution changes a codon but not the amino acid incorporated into a protein. Which property best explains this outcome?A. All codons encode the same amino acid.B. The genetic code is redundant, with some amino acids specified by multiple codons.C. Every substitution creates a stop codon.D. Ribosomes never read mRNA.

Question 15 · Unit 7: Natural Selection · challenge

In a large diploid population at Hardy-Weinberg equilibrium for a two-allele locus, the recessive allele frequency is 0.2. What fraction of individuals is expected to be heterozygous?A. 0.04B. 0.16C. 0.32D. 0.64

Question 16 · Unit 8: Ecology · challenge

A population follows the logistic model dN/dt = rN(1 - N/K), with r > 0 and K > 0. For 0 <= N <= K, at what population size is its instantaneous growth rate greatest?A. 0B. K/4C. K/2D. K

AP Biology practice questions