100+ Free Pennsylvania Keystone Exam — Biology Practice Questions

Prepare for the Pennsylvania Keystone Exam — Biology (PDE STEELS Aligned) exam with instant access — no signup required.

✓ No registration✓ No credit card✓ No hidden fees✓ Start practicing immediately

100+ Questions

100% Free

Loading practice questions...

Same family resources

Explore More Pennsylvania Keystone Exams

Continue into nearby exams from the same family. Each card keeps practice questions, study guides, flashcards, videos, and articles in one place.

Pennsylvania Keystone Exam — Algebra I

Practice Questions100 questions

Pennsylvania Keystone Exam — Literature

Practice Questions100 questions

2026 Statistics

Key Facts: Pennsylvania Keystone Exam — Biology Exam

100 Qs

Practice Questions

OpenExamPrep Practice Bank

2 Modules

Module A (Cells) & Module B (Continuity)

PA Department of Education

50% / 50%

Module Weighting

PDE Biology Assessment Anchors

1500+

Proficient Scaled Score Cut

PDE Keystone Scoring Guide

The PA Keystone Biology exam tests core life science concepts split equally into Module A (Cells and Cell Processes) and Module B (Continuity and Unity of Life). This 100-question practice bank covers bioenergetics, macromolecules, transport, cell structure, cell division, genetics & DNA technology, evolution, and ecology.

Sample Pennsylvania Keystone Exam — Biology Practice Questions

Try these sample questions to test your Pennsylvania Keystone Exam — Biology exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Water molecules form hydrogen bonds between adjacent molecules because of their polar covalent structure. Which property of water directly results from hydrogen bonding and allows water striders to walk across the surface of a pond?

A.High specific heat capacity

B.Surface tension

C.Universal solvent capability

D.Expansion upon freezing

Explanation: Surface tension is caused by cohesion—the attraction between polar water molecules due to hydrogen bonding. At the surface of a liquid body of water, hydrogen bonds create an elastic-like membrane strong enough to support small organisms like water striders.

2Enzymes are biological catalysts that speed up chemical reactions in living organisms. How do enzymes increase the rate of a biochemical reaction?

A.By increasing the temperature of the cellular environment

B.By lowering the activation energy required for the reaction

C.By adding energy to the substrates to transform them into products

D.By permanently changing their shape to match the substrate

Explanation: Enzymes speed up biochemical reactions by binding substrates at their active sites and lowering the activation energy—the minimum energy required to initiate the chemical transformation.

3Adenosine triphosphate (ATP) serves as the primary energy currency of the cell. Which process directly yields the energy needed to power cellular work such as muscle contraction?

A.Synthesis of ATP from ADP and inorganic phosphate

B.Hydrolysis of the terminal phosphate bond in ATP

C.Binding of glucose to the active site of ATP synthase

D.Reduction of NADP+ to NADPH during photosynthesis

Explanation: Hydrolysis of ATP removes its terminal phosphate group, breaking a high-energy phosphoanhydride bond and yielding ADP, inorganic phosphate (Pi), and free energy used to drive endergonic cellular reactions.

4Which general chemical equation correctly summarizes the overall process of aerobic cellular respiration?

A.6CO2 + 6H2O + Light Energy -> C6H12O6 + 6O2

B.C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP Energy

C.C6H12O6 + 6CO2 -> 6H2O + 6O2 + ATP Energy

D.6CO2 + C6H12O6 -> 6O2 + 6H2O + Light Energy

Explanation: Aerobic cellular respiration breaks down one molecule of glucose (C6H12O6) using 6 molecules of oxygen (6O2) to yield 6 carbon dioxide molecules (6CO2), 6 water molecules (6H2O), and chemical energy in the form of ATP.

5A student measures the rate of an enzyme-catalyzed reaction across a temperature range from 10°C to 60°C. The reaction rate rises steadily until 37°C, after which it drops sharply to zero by 55°C. What best explains the rapid decline in activity above 37°C?

A.The substrate molecules are destroyed by excessive thermal energy

B.The enzyme loses its tertiary structure due to denaturation of hydrogen bonds

C.The enzyme converts into a different functional enzyme isoform

D.The activation energy of the reaction increases beyond normal biological limits

Explanation: Elevated temperatures disrupt weak interactions—such as hydrogen bonds and ionic bonds—that maintain the enzyme's specific 3D tertiary structure. This causes denaturation, altering the active site shape so substrates can no longer bind.

6During the light-dependent reactions of photosynthesis, water molecules are split in a process known as photolysis. What are the essential biological products of photolysis?

A.Carbon dioxide, ATP, and glucose

B.Electrons, hydrogen ions (protons), and oxygen gas

C.NADPH, rubisco, and pyruvate

D.G3P, ADP, and water

Explanation: Photolysis in Photosystem II splits H2O into 2 H+ (protons that contribute to the thylakoid membrane proton gradient), 2 electrons (which replace oxidized P680 chlorophyll electrons), and 1/2 O2 gas (released as a byproduct).

7In plant chloroplasts, where do the light-independent reactions (Calvin cycle) take place, and what is their primary carbon input?

A.Thylakoid lumen; O2

B.Stroma; CO2

C.Outer membrane; C6H12O6

D.Cristae; Pyruvate

Explanation: The Calvin cycle occurs in the fluid-filled stroma of the chloroplast. It utilizes carbon dioxide (CO2) from the atmosphere, along with ATP and NADPH generated in the thylakoid membranes, to synthesize high-energy sugars.

8Glycolysis is the first metabolic pathway of cellular respiration. Which statement accurately describes its location and net energy yield per molecule of glucose?

A.Mitochondrial matrix; net yield of 36 ATP

B.Cytoplasm; net yield of 2 ATP and 2 NADH

C.Inner mitochondrial membrane; net yield of 4 ATP and 2 FADH2

D.Chloroplast stroma; net yield of 2 ATP and 2 NADPH

Explanation: Glycolysis takes place in the cytoplasm of anaerobic and aerobic cells. It invests 2 ATP to break down glucose into 2 pyruvate molecules, producing 4 ATP (net 2 ATP) and 2 NADH molecules.

9Cyanide inhibits cytochrome c oxidase, a protein complex in the inner mitochondrial membrane. What is the immediate biochemical consequence of cyanide poisoning on cellular respiration?

A.Glycolysis stops producing pyruvate

B.Proton pumping across the inner membrane ceases, halting ATP synthesis by chemiosmosis

C.Glucose accumulates in the mitochondrial matrix

D.The cell shifts entirely to oxygenic photosynthesis

Explanation: Inhibiting cytochrome c oxidase prevents electron transfer to oxygen (the final electron acceptor). This stops electron flow through the electron transport chain, ending proton pumping and collapsing the electrochemical gradient needed by ATP synthase.

10Under anaerobic conditions, human skeletal muscle cells perform lactic acid fermentation. What is the primary biological purpose of fermentation in these cells?

A.To produce extra oxygen gas for the mitochondria

B.To regenerate NAD+ from NADH so glycolysis can continue generating ATP

C.To convert lactic acid directly into glucose without energy loss

D.To yield 32 additional ATP molecules per glucose molecule

Explanation: Glycolysis requires NAD+ to accept electrons during glucose oxidation. Under anaerobic conditions, fermentation transfers electrons from NADH to pyruvate (forming lactate), regenerating NAD+ so glycolysis can continue producing 2 ATP per glucose.

About the Pennsylvania Keystone Exam — Biology Exam

The Pennsylvania Keystone Exam in Biology measures student proficiency in high school biology assessment anchors aligned to PA STEELS standards. Module A covers Cells and Cell Processes (50%), and Module B covers Continuity and Unity of Life (50%).

Assessment

Two modules: Module 1 (Cells and Cell Processes) and Module 2 (Continuity and Unity of Life), each with multiple-choice and constructed-response items aligned to the Biology Assessment Anchors and Eligible Content.

Time Limit

Untimed; PDE estimates about 72 minutes of testing per module (82-87 minutes per module including administration). Delivered online only beginning with the Spring 2026 administration.

Passing Score

1500-1548 is Proficient and 1549-1800 is Advanced on the 1200-1800 Keystone scale

Exam Fee

Free (Pennsylvania Department of Education / DRC)

Pennsylvania Keystone Exam — Biology Exam Content Outline

15%

Basic Biology and Bioenergetics

Biochemistry, properties of water, enzyme function, ATP structure/cycle, cellular respiration, and photosynthesis.

10%

Chemical Basis of Life

Structure and function of carbohydrates, lipids, proteins, nucleic acids, monomer-polymer relationships, and dehydration synthesis/hydrolysis.

15%

Homeostasis and Transport

Fluid mosaic membrane model, passive transport (diffusion, osmosis, facilitated diffusion), active transport (pumps, endocytosis, exocytosis), and osmotic pressure balance.

10%

Cell Structure and Function

Prokaryotic vs. eukaryotic cell architecture, organelle structure and function (nucleus, mitochondria, chloroplast, ribosome, ER, Golgi), and cellular hierarchy.

10%

Cell Growth and Reproduction

The cell cycle, interphase, mitotic stages, cytokinesis, meiosis, homologous chromosomes, crossing over, and non-disjunction.

15%

Genetics and DNA Technology

Mendelian genetics, Punnett squares, codominance, incomplete dominance, sex-linked traits, DNA replication, transcription, translation, mutations, PCR, and gel electrophoresis.

15%

Theory of Evolution

Natural selection, mechanisms of evolution (mutation, gene flow, genetic drift), anatomical evidence (homologous/analogous), fossils, speciation, and phylogenetic analysis.

10%

Ecology and Ecosystems

Energy pyramids, food webs, biogeochemical cycles (carbon, nitrogen), population growth curves (exponential, logistic), ecological succession, and human impacts.

How to Pass the Pennsylvania Keystone Exam — Biology Exam

What You Need to Know

Passing score: 1500-1548 is Proficient and 1549-1800 is Advanced on the 1200-1800 Keystone scale
Assessment: Two modules: Module 1 (Cells and Cell Processes) and Module 2 (Continuity and Unity of Life), each with multiple-choice and constructed-response items aligned to the Biology Assessment Anchors and Eligible Content.
Time limit: Untimed; PDE estimates about 72 minutes of testing per module (82-87 minutes per module including administration). Delivered online only beginning with the Spring 2026 administration.
Exam fee: Free

Keys to Passing

Work through all 100 available questions
Review every answer and explanation
Track weak areas and revisit them
Use our AI tutor for tough concepts

Pennsylvania Keystone Exam — Biology Study Tips from Top Performers

1Master Module A transport mechanisms (osmosis, active vs. passive) and bioenergetics (photosynthesis and respiration equations).

2Practice monohybrid and dihybrid Punnett squares, transcription/translation codon matching, and gel electrophoresis analysis for Module B.

3Understand evolutionary mechanisms like genetic drift vs. natural selection, and how phylogenetic trees depict common ancestry.

4Use this 100-question practice bank to test scenario-based reasoning and review the detailed feedback for incorrect options.

Frequently Asked Questions

What is the PA Keystone Biology Exam?

The PA Keystone Biology Exam is an end-of-course state assessment developed by the Pennsylvania Department of Education (PDE) to evaluate high school students' mastery of biology assessment anchors.

How is the Keystone Biology exam structured?

The exam is divided into two modules: Module A (Cells and Cell Processes) and Module B (Continuity and Unity of Life), each accounting for 50% of the overall score.

What score is required to pass the Keystone Biology exam?

Pennsylvania uses performance levels: Below Basic, Basic, Proficient, and Advanced. Achieving 'Proficient' (typically a scaled score of 1500 or higher) satisfies the state graduation requirement.

Are calculators or reference sheets allowed?

Standard formula and reference guides may be provided during testing where applicable. Calculators are generally not needed for high school biology.