MCAT Science Content Guide 2026: Biochemistry, Pharmacology & More

MCAT Subject Overview

The MCAT (Medical College Admission Test) is a 7.5-hour, 230-question standardized exam that tests scientific knowledge and reasoning skills across four sections. Each section is scored from 118 to 132, for a total score range of 472 to 528. Medical schools use MCAT scores as a key component of admissions decisions alongside GPA, clinical experience, letters of recommendation, and personal statements.

The four MCAT sections are: Biological and Biochemical Foundations of Living Systems (Bio/Biochem — 59 questions, 95 minutes); Chemical and Physical Foundations of Biological Systems (Chem/Physics — 59 questions, 95 minutes); Psychological, Social, and Biological Foundations of Behavior (Psych/Soc — 59 questions, 95 minutes); and Critical Analysis and Reasoning Skills (CARS — 53 questions, 90 minutes). The exam also includes two 10-minute breaks and one 30-minute break, making the total testing time from check-in to completion approximately 7 hours 30 minutes.

The MCAT is passage-based — most questions are associated with passages describing experimental data, scientific literature, or research scenarios. Foundational science knowledge is necessary but not sufficient; you must be able to apply that knowledge to novel experimental contexts. This is the defining challenge of MCAT preparation: knowing biochemistry and physiology deeply enough to answer questions about experimental situations you have never specifically studied, rather than just recalling textbook facts.

Biology and Biochemistry (Bio/Biochem Section)

The Biological and Biochemical Foundations of Living Systems section tests your knowledge of biology, biochemistry, and organic chemistry with approximately 65% biology/biochemistry and 35% organic chemistry. This is typically the most heavily-weighted content section for pre-medical students.

Core Biology Topics

Cellular biology is foundational — know cell structure, organelle functions, cellular respiration (glycolysis, TCA cycle, oxidative phosphorylation, fermentation), cell cycle and mitosis/meiosis, and the mechanisms of cell signaling. Molecular biology topics include DNA structure and replication, transcription and translation, gene regulation (lac operon, eukaryotic gene expression), recombinant DNA technology, and common experimental techniques (PCR, gel electrophoresis, ELISA, Southern blot). Genetics covers Mendelian inheritance, Hardy-Weinberg equilibrium, mutations, and the relationship between genotype and phenotype. Organ systems — particularly cardiovascular, renal, respiratory, endocrine, nervous, immune, and digestive — are tested with experimental passages describing pathological conditions and physiological responses.

Biochemistry: High-Priority Topics

Biochemistry is heavily tested and often the area where pre-medical students have the most to learn. High-priority biochemistry topics: amino acid structure and properties (know all 20 amino acids, their side chains, and which are polar, nonpolar, acidic, or basic), protein structure and folding (primary through quaternary structure), enzyme kinetics (Michaelis-Menten, Km, Vmax, competitive/non-competitive inhibition), enzyme regulation (allosteric regulation, covalent modification, feedback inhibition), metabolic pathways (glycolysis, gluconeogenesis, glycogenolysis, fatty acid oxidation and synthesis, the TCA cycle, electron transport chain and ATP yield), and lipid biochemistry (phospholipids, steroids, bile salts).

Pharmacology and Drug Mechanisms

Pharmacology appears throughout the MCAT, particularly in Bio/Biochem and Chem/Physics passage contexts. The MCAT does not test specific drug names comprehensively, but tests understanding of drug mechanisms at the molecular and physiological levels. Key pharmacology concepts: receptor pharmacology (agonists, antagonists, partial agonists), dose-response relationships, enzyme inhibition (many drugs work by inhibiting enzymes — know competitive vs. irreversible inhibition mechanisms), pharmacokinetics concepts (absorption, distribution, metabolism, elimination — ADME), and the mechanism of action of broad drug classes (beta-blockers as receptor antagonists, ACE inhibitors as enzyme inhibitors, NSAIDs as COX inhibitors, statins as HMG-CoA reductase inhibitors). Passages presenting novel drugs will describe their mechanism in the passage — your job is to apply receptor and enzyme pharmacology principles to understand and predict the drug's effects.

Chemistry and Physics (Chem/Physics Section)

The Chemical and Physical Foundations of Biological Systems section tests general chemistry, organic chemistry, biochemistry, and physics in a biological context. Approximately 30% of questions involve physics and math, 25% general chemistry, 25% organic chemistry and biochemistry, and the remaining applied biology. This section is often considered the most challenging for students with a stronger biology background.

General Chemistry

General chemistry topics tested include: atomic structure (electron orbitals, periodic trends), chemical bonding (ionic, covalent, hydrogen bonding, intermolecular forces), acid-base chemistry (pH, pKa, buffers, Henderson-Hasselbalch equation), electrochemistry (galvanic cells, Nernst equation), thermodynamics (enthalpy, entropy, Gibbs free energy, equilibrium constants), kinetics (rate laws, activation energy, Arrhenius equation), and gas laws (ideal gas law, partial pressures). The Henderson-Hasselbalch equation is particularly important — know how to use it to calculate pH in buffer systems, which is directly tested in physiology contexts.

Organic Chemistry

MCAT organic chemistry emphasizes mechanisms and functional group properties rather than synthesis. High-priority topics: functional group recognition (alcohols, aldehydes, ketones, carboxylic acids, esters, amines, amides), nucleophilic substitution and elimination reactions (SN1, SN2, E1, E2 — and how substrate structure, solvent, and nucleophile strength determine which mechanism operates), carbonyl chemistry (nucleophilic addition to aldehydes and ketones, acyl substitution at esters and amides), and spectroscopy (IR for functional group identification, NMR for structure determination, mass spectrometry for molecular weight). Stereochemistry — chirality, R/S designation, enantiomers, diastereomers, and their biological implications — is tested regularly.

Physics

MCAT physics topics are tested in biological and medical contexts. Key areas: fluid dynamics (Bernoulli's equation, viscosity, flow rate — applied to blood flow), optics (mirrors, lenses, image formation — applied to the eye), electricity and magnetism (circuits, capacitors — applied to nerve conduction and cardiac physiology), sound and waves (frequency, amplitude, Doppler effect — applied to ultrasound and hearing), and mechanics (forces, torque, work, energy — applied to musculoskeletal biomechanics). Math on the MCAT is limited to algebra and basic trigonometry — no calculus — but you must calculate quickly without a calculator.

Psychology and Sociology (Psych/Soc Section)

The Psychological, Social, and Biological Foundations of Behavior section was added to the MCAT in 2015 and covers the psychological and sociological sciences underlying human health and behavior. This section tests considerably different content than the natural science sections and rewards students who treat it seriously rather than assuming it is easy.

Psychology Topics

Psychological topics span multiple levels of analysis: biopsychology (brain structures and functions, neurotransmitter systems, the peripheral and central nervous system, the biological basis of behavior), sensation and perception (sensory processing, signal detection theory, perceptual organization), learning and memory (classical and operant conditioning, observational learning, types of memory, memory encoding/storage/retrieval), cognition (problem solving, decision making, cognitive biases), motivation and emotion (theories of motivation, emotion regulation, stress response), development (stages of development across the lifespan, attachment theory, Piaget's cognitive stages, Erikson's psychosocial stages), and psychological disorders (diagnostic criteria for major disorders, biological and psychological treatment approaches).

Sociology Topics

Sociology topics include: social stratification (social class, socioeconomic status, social mobility, health disparities by class, race, and gender), social institutions (family, education, healthcare system, economy), culture (cultural norms, values, material vs. non-material culture, cultural relativism), sociological theory (functionalism, conflict theory, symbolic interactionism, social constructionism), group dynamics (conformity, obedience, social facilitation, groupthink), and population health (social determinants of health, health disparities, epidemiology concepts). MCAT sociology passages often present research studies examining social inequities in health outcomes — being able to analyze these findings critically is as important as knowing the underlying sociological concepts.

Critical Analysis and Reasoning Skills (CARS)

The CARS section is unique among the four MCAT sections: it tests no specific scientific content whatsoever. Passages are drawn from humanities (philosophy, ethics, arts, literature criticism) and social sciences (economics, political science, anthropology, sociology) and are specifically chosen from fields that pre-medical students are unlikely to have studied deeply. This is intentional — CARS tests your ability to analyze arguments and extract meaning from challenging texts regardless of the subject matter.

What CARS Tests

CARS questions fall into three categories: Foundations of Comprehension (understanding the author's main argument and specific claims — 30% of questions), Reasoning Within the Text (recognizing how different parts of the passage relate to each other and to the author's argument — 30%), and Reasoning Beyond the Text (applying information from the passage to new contexts, evaluating the impact of new information on the author's argument — 40%). The highest-proportion question type — Reasoning Beyond the Text — requires the most sophisticated reading comprehension: not just understanding what the author says, but predicting how the author would respond to new information or how the author's argument applies in a novel context.

CARS Strategy

Most high CARS scorers read every word of every passage carefully before answering questions, rather than skimming. The passages are challenging specifically because they reward close reading — answers to many questions are directly supported by precise language in the passage that casual readers miss. Practice active reading habits: identify the author's main argument, note each paragraph's function, and track where the author's own view differs from views being described or critiqued. For CARS specifically, the volume of practice is less important than the quality of practice — reading 2 passages with deep analysis is more valuable than rushing through 6 passages superficially.