Study guides & original practice
Eight original short-answer questions, one topic from each course unit. Answer on paper before opening the explanations. This is a short diagnostic, not a full-length exam or a predicted AP score.
Free to use. No account required. Allow about 15–20 minutes, then review each explanation.
Why can a large body of water moderate nearby temperature changes, and what molecular interaction helps explain this?
Water has a high specific heat: it can absorb or release substantial heat with a relatively small temperature change. Hydrogen bonding between water molecules contributes to this property. Energy absorbed can disrupt these interactions rather than immediately producing a large increase in molecular motion.
A cell containing 0.30 M nonpenetrating solute is placed in a large bath of 0.10 M nonpenetrating solute. Predict the initial net movement of water.
Water initially moves into the cell by osmosis, assuming equal pressure and a membrane permeable to water. The bath is hypotonic relative to the cell; the higher solute concentration inside lowers water potential. Solute does not have to cross for water to move.
An enzyme makes 12 units of product per minute at 25°C and 20 at 35°C. Can you conclude that 45°C will produce 28 units per minute?
No. Two observations do not establish a linear relationship across temperatures. Higher temperature may increase reaction rate over a limited range, but loss of enzyme structure can reduce activity. Test additional temperatures while holding enzyme concentration, substrate concentration and pH constant.
A mutation prevents a receptor from binding its signal molecule. Its downstream relay proteins are intact. Predict the response to adding more signal.
If binding is completely prevented, more signal will not activate this receptor pathway. A functioning downstream pathway does not compensate for a missing initiating event. A partial reduction in affinity could behave differently; the question specifies no binding.
Two heterozygous parents, Aa and Aa, have offspring. Under complete dominance, what fraction is expected to show the recessive phenotype?
One quarter. The expected genotypes are 1 AA : 2 Aa : 1 aa; only aa has the recessive phenotype. This is a probability for each offspring, not a guarantee that every group of four contains exactly one recessive individual.
A mutation changes a DNA coding-strand triplet from GAA to GAG. Both corresponding mRNA codons encode glutamate. What can you conclude about this amino acid?
It is unchanged: the mRNA codon changes from GAA to GAG, but both specify glutamate. The genetic code is redundant. This alone does not prove that every aspect of gene expression or organismal fitness is unaffected.
After repeated antibiotic exposure, resistant bacteria become more common. Did the antibiotic teach individual bacteria to become resistant?
No. Resistance can arise through mutation or acquisition of resistance genes. Antibiotic exposure favors resistant variants because susceptible bacteria leave fewer surviving descendants. Selection changes the population; it is not purposeful training of individuals.
A field has 100 plants in 2024 and 130 in 2025. A researcher credits added fertilizer, but there is no untreated comparison plot. What is the main limitation?
The increase alone does not isolate the effect of fertilizer. Rainfall, seed input and other conditions could also change abundance. Replicated treated and untreated plots, with comparable starting conditions, would support a stronger causal test.
For each answer, mark “explained independently,” “partly explained,” or “needed the solution.” A correct guess is still worth reviewing. This self-check is not an official scoring rubric.
If you wrote “solute moves into the cell” for question 2, separate the two substances: the solute cannot cross in this example; water can. A useful follow-up card is “What moves during osmosis, and in which direction under equal pressure?”
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The topics follow the eight-unit organization of the College Board AP Biology course. For official exam format and practice resources, use the AP Biology exam page. These questions are original Exam Cat material, not released College Board questions. Exam Cat is not affiliated with or endorsed by College Board.
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