The graph below shows enzyme activity versus temperature. (Graph not shown. Assume optimal activity at 37°C, activity declines outside this range.) What is the best interpretation?

Enzyme activity peaks around 37°C.

Enzyme activity increases with temperature without limit.

Enzymes are most active at 0°C.

High temperatures enhance enzyme stability.

AP Biology

Free AP Biology Practice Questions

10 sample questions for the AP Biology, with the correct answer and an explanation for each. No account needed. Try each one before you open the answer.

Sections covered on the exam: Chemistry of Life, Science Practices, Cell Structure, Function, and Energetics, Cellular Energetics, Cell Communication and Cell Cycle, Heredity, Gene Expression and Regulation, Natural Selection, Ecology.

Question 1 · Chemistry of Life
Which property of water allows it to dissolve many polar and ionic substances?
- A.High surface tension
- B.Cohesion
- C.Universal solvent behavior
- D.Low vapor pressure
Show answer and explanation
Answer: C. Universal solvent behavior
Water’s polarity enables it to surround and dissolve many polar and ionic molecules, making it an excellent solvent.
Question 2 · Science Practices
The graph below shows enzyme activity versus temperature.
(Graph not shown. Assume optimal activity at 37°C, activity declines outside this range.)
What is the best interpretation?
- A.Enzyme activity peaks around 37°C.
- B.Enzyme activity increases with temperature without limit.
- C.Enzymes are most active at 0°C.
- D.High temperatures enhance enzyme stability.
Show answer and explanation
Answer: A. Enzyme activity peaks around 37°C.
Most human enzymes function optimally near body temperature (37°C).
Question 3 · Cellular Energetics
Which process generates the most ATP in cellular respiration?
- A.Glycolysis
- B.Krebs cycle
- C.Fermentation
- D.Electron transport chain
Show answer and explanation
Answer: D. Electron transport chain
The electron transport chain in the mitochondria produces the majority of ATP during aerobic respiration.
Question 4 · Heredity
In blood type inheritance, an individual with genotype IAIB has type AB blood. This is an example of:
- A.Incomplete dominance
- B.Codominance
- C.Epistasis
- D.Polygenic inheritance
Show answer and explanation
Answer: B. Codominance
Both alleles are fully expressed in codominance, as seen in blood type AB.
Question 5 · Natural Selection
Which of the following increases the frequency of beneficial traits in a population?
- A.Natural selection
- B.Gene flow
- C.Genetic drift
- D.Random mating
Show answer and explanation
Answer: A. Natural selection
Natural selection favors traits that enhance survival and reproduction, increasing their frequency in the gene pool.
Question 6 · Chemistry of Life
As before, this section includes 5 topics, and we’ll provide 11 new, non-repeating questions (~2–3 per topic).
Which property of water helps transport nutrients and waste in biological organisms?
- A.High viscosity
- B.Neutral pH
- C.Cohesion and adhesion
- D.Nonpolar nature
Show answer and explanation
Answer: C. Cohesion and adhesion
Cohesion helps water molecules stick together, and adhesion allows them to cling to surfaces like blood vessel walls or plant xylem.
Question 7 · Science Practices
Which type of graph is best for showing changes in enzyme activity over a range of temperatures?
- A.Pie chart
- B.Line graph
- C.Bar chart
- D.Histogram
Show answer and explanation
Answer: B. Line graph
Line graphs effectively show trends over continuous variables like temperature.
Question 8 · Cellular Energetics
How many net ATP are produced during glycolysis?
- A.4
- B.2
- C.6
- D.8
Show answer and explanation
Answer: B. 2
Glycolysis produces 4 ATP, but 2 are used, resulting in a net gain of 2 ATP.
Question 9 · Heredity
A woman with type A blood and a man with type B blood have a child with type O blood. What are their genotypes?
- A.IAIA and IBIB
- B.IAi and IBi
- C.IAIB and ii
- D.IAIA and ii
Show answer and explanation
Answer: B. IAi and IBi
Both parents must be heterozygous (IAi and IBi) to produce a child with genotype ii (type O).
Question 10 · Natural Selection
Gene flow between populations typically results in:
- A.Greater genetic similarity
- B.Decreased fitness
- C.Reduced variation
- D.Increased genetic differences
Show answer and explanation
Answer: A. Greater genetic similarity
Gene flow introduces new alleles into a population, making populations more genetically similar.

Keep practicing for the AP Biology

TTP Prep has 200 AP Biology practice questions with explanations, timed and mock-exam modes, 119 flashcards, interactive lessons, a printable cheat sheet and a readiness score. Start free, no card needed.

Take a free Quick 10 See everything in the AP Biology prep