100+ Free OAT Natural Sciences Practice Questions

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In the Brønsted-Lowry theory, which species acts as a proton (H+) donor?

Nucleophile

Brønsted-Lowry acid

Lewis base

Brønsted-Lowry base

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OAT (Optometry Admission Test)

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2026 Statistics

Key Facts: OAT Natural Sciences Exam

100 questions / 90 minutes

Survey of Natural Sciences length

ADA 2026 OAT Candidate Guide

40 Biology / 30 Gen Chem / 30 Org Chem

Question distribution

ADA 2026 OAT Candidate Guide

$520

Full OAT exam fee

ADA OAT Program (2025–2026)

200–400 scale, median 300

OAT score scale

ADA OAT User's Guide

All U.S. optometry schools

OAT scores accepted by

ASCO FAQ

90-day minimum wait

Between OAT retakes

ASCO OAT Policy

The OAT Survey of Natural Sciences comprises 100 questions in 90 minutes across Biology (40 items), General Chemistry (30 items), and Organic Chemistry (30 items), scored on a 200–400 scale (ASCO, 2026 Candidate Guide). The exam is administered year-round at Prometric centers and accepted by all U.S. optometry schools. The fee for the full OAT is $520, with partial fee waivers available (ADA). Competitive applicants typically aim for a Total Science score of 320 or higher. Preparation requires mastery of first-year college biology, general chemistry, and organic chemistry.

Sample OAT Natural Sciences Practice Questions

Try these sample questions to test your OAT Natural Sciences exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which organelle is primarily responsible for ATP synthesis via oxidative phosphorylation?

A.Smooth endoplasmic reticulum

B.Ribosome

C.Mitochondrion

D.Golgi apparatus

Explanation: Mitochondria contain the electron transport chain and ATP synthase on their inner membrane, making them the primary site of oxidative phosphorylation. This process generates the majority of cellular ATP from NADH and FADH2.

2During cellular respiration, what is the net yield of ATP molecules from glycolysis of one glucose molecule?

A.2 ATP

B.4 ATP

C.32 ATP

D.38 ATP

Explanation: Glycolysis produces 4 ATP by substrate-level phosphorylation but consumes 2 ATP in the preparatory phase, giving a net yield of 2 ATP per glucose. The 2 NADH also produced carry electrons to later stages.

3Which phase of mitosis is characterized by chromosomes aligning at the cell's equatorial plate?

A.Prophase

B.Metaphase

C.Anaphase

D.Telophase

Explanation: During metaphase, chromosomes reach maximum condensation and align along the metaphase plate (equatorial plane) under tension from spindle fibers attached to kinetochores. This alignment ensures equal segregation to daughter cells.

4A phospholipid bilayer membrane is described as 'selectively permeable.' Which molecule can most readily pass through the membrane WITHOUT a transporter?

A.Glucose

B.Sodium ion (Na+)

C.Carbon dioxide (CO2)

D.ATP

Explanation: CO2 is a small, nonpolar molecule that diffuses freely through the lipid bilayer. The hydrophobic core of the membrane blocks charged ions and large polar molecules like glucose and ATP.

5Which cellular process uses light energy to convert CO2 and H2O into glucose?

A.Cellular respiration

B.Fermentation

C.Photosynthesis

D.Chemosynthesis

Explanation: Photosynthesis occurs in chloroplasts and uses light energy to drive the conversion of CO2 and H2O into glucose and O2 via the light-dependent reactions (in thylakoids) and the Calvin cycle (in the stroma).

6In DNA replication, which enzyme synthesizes new DNA strands by adding nucleotides in the 5'→3' direction?

A.DNA ligase

B.Helicase

C.Primase

D.DNA polymerase III

Explanation: DNA polymerase III (in prokaryotes; Pol delta/epsilon in eukaryotes) is the main replicative polymerase that reads the template 3'→5' and synthesizes the new strand 5'→3'. It also has 3'→5' proofreading exonuclease activity.

7Which type of RNA carries amino acids to the ribosome during translation?

A.mRNA

B.rRNA

C.tRNA

D.snRNA

Explanation: Transfer RNA (tRNA) has an anticodon that base-pairs with the mRNA codon and an acceptor arm at its 3' end that is charged with the corresponding amino acid by aminoacyl-tRNA synthetases.

8Which kingdom includes multicellular, heterotrophic organisms with cell walls made of chitin?

A.Plantae

B.Animalia

C.Fungi

D.Protista

Explanation: Fungi are multicellular (or unicellular in the case of yeasts), heterotrophic (absorptive nutrition), and have cell walls composed of chitin — a nitrogen-containing polysaccharide distinct from the cellulose of plant cell walls.

9A bacteriophage injects its DNA into a host bacterium, and the viral DNA integrates into the host genome, remaining dormant. This describes which viral lifecycle?

A.Lytic cycle

B.Lysogenic cycle

C.Transduction

D.Transformation

Explanation: In the lysogenic cycle, viral DNA (prophage) integrates into the host chromosome and is replicated along with the bacterial genome without immediately destroying the host. Stress can trigger induction into the lytic cycle.

10Which of the following correctly pairs a heart structure with its function?

A.Tricuspid valve — prevents backflow from right ventricle to right atrium

B.Mitral valve — separates the two ventricles

C.Pulmonary semilunar valve — prevents backflow from left ventricle to aorta

D.SA node — located in the left ventricle wall

Explanation: The tricuspid (right atrioventricular) valve has three cusps and lies between the right atrium and right ventricle, preventing backflow when the right ventricle contracts.

About the OAT Natural Sciences Exam

The OAT Survey of Natural Sciences is the first and most content-heavy section of the Optometry Admission Test (OAT). It consists of 100 multiple-choice questions divided into Biology (40), General Chemistry (30), and Organic Chemistry (30), completed in 90 minutes. Separate subscores are reported for each of the three sciences. An on-screen periodic table is provided.

Questions

100 scored questions

Time Limit

90 minutes

Passing Score

200–400 scale (median 300); competitive programs seek 320–350+

Exam Fee

$520 (full OAT exam) (American Dental Association (ADA) on behalf of ASCO)

OAT Natural Sciences Exam Content Outline

40 questions

Biology

Cell & molecular biology, diversity of life, vertebrate anatomy & physiology, developmental biology, genetics, evolution, ecology, and behavior.

30 questions

General Chemistry

Stoichiometry, gases, liquids & solids, solutions, acids & bases, chemical equilibria, thermodynamics, kinetics, redox/electrochemistry, atomic & molecular structure, periodic properties, nuclear chemistry, and laboratory techniques.

30 questions

Organic Chemistry

Mechanisms, chemical & physical properties, spectroscopy (IR, NMR), stereochemistry, nomenclature, reactions of functional groups, acid-base chemistry, aromatics, and laboratory techniques.

How to Pass the OAT Natural Sciences Exam

What You Need to Know

Passing score: 200–400 scale (median 300); competitive programs seek 320–350+
Exam length: 100 questions
Time limit: 90 minutes
Exam fee: $520 (full OAT exam)

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

OAT Natural Sciences Study Tips from Top Performers

1Treat the three subsections as separate mini-exams. Study Biology, General Chemistry, and Organic Chemistry independently before integrating them into timed full-section practice.

2Use the Kaplan time-allocation strategy: ~20 min for Biology (0.5 min/q), ~37.5 min for Gen Chem (1.25 min/q), ~30 min for Org Chem (1 min/q), and 2.5 min to review flagged items.

3For Organic Chemistry, master reaction mechanisms rather than memorizing individual reactions. Understanding SN1, SN2, E1, E2, and EAS mechanisms lets you predict products for hundreds of substrate/reagent combinations.

4For General Chemistry, practice stoichiometry and gas law calculations until they are second nature. These appear frequently and require accurate mental math under time pressure.

5For Biology, prioritize high-yield systems that intersect with optometry: the eye and vision, the nervous system, and cardiovascular/respiratory physiology. Genetics and cell biology are heavily tested.

Frequently Asked Questions

How many questions are on the OAT Survey of Natural Sciences?

The Survey of Natural Sciences contains 100 multiple-choice questions: 40 Biology, 30 General Chemistry, and 30 Organic Chemistry. You have 90 minutes total, which averages about 54 seconds per question.

Is the OAT Natural Sciences section scored separately from the rest of the OAT?

Yes. The OAT reports a Total Science (TS) score combining all three natural sciences subscores, plus individual Biology, General Chemistry, and Organic Chemistry subscores. These are separate from Reading Comprehension, Physics, and Quantitative Reasoning scores. All are on the 200–400 scale.

What is a good score on the OAT Survey of Natural Sciences?

The median score for each section is 300 (on the 200–400 scale). Competitive optometry programs typically want a Total Science score of 320 or higher, with the top 25% of applicants scoring around 350+. Always check each school's stated average OAT scores.

Is an on-screen periodic table provided during the OAT Natural Sciences section?

Yes. According to the official 2026 OAT Candidate Guide, an on-screen periodic table is provided for the Survey of Natural Sciences section.

How long should I study for the OAT Natural Sciences section?

Most test-prep experts recommend 150–250 hours of total OAT preparation. The Survey of Natural Sciences is the most content-heavy section and typically requires 80–120 hours. Focus on first-year biology, general chemistry, and organic chemistry coursework as your foundation.

Can I retake the OAT if I am unhappy with my Natural Sciences score?

Yes. Candidates must wait at least 90 days between attempts. After three attempts, you must apply for permission and may only retest once every 12 months. Scores from the four most recent attempts and total number of attempts are reported to programs.