Biochemistry sits at the intersection of biology, chemistry, and medicine. It is the molecular language of life, explaining how biological molecules interact, how metabolic pathways produce and consume energy, and how genetic information is expressed and regulated. For pre-health students, biochemistry is both a critical prerequisite course and one of the most heavily tested subjects on the MCAT®. The MCAT® Bio/Biochem section dedicates approximately 25 percent of its content to biochemistry, and biochemistry concepts appear throughout the Chem/Phys section as well. This guide covers the key topics, free resources, and study strategies for mastering this essential subject.

Key Topics to Master

Amino Acids and Protein Structure: Know all 20 standard amino acids by name, one-letter and three-letter codes, side chain properties (nonpolar, polar uncharged, positively charged, negatively charged), and pKa values for ionizable groups. Understand the four levels of protein structure (primary, secondary, tertiary, quaternary) and the forces that stabilize each level (peptide bonds, hydrogen bonds, hydrophobic interactions, disulfide bonds, ionic interactions). Protein misfolding and denaturation are clinically relevant (prion diseases, sickle cell disease). This is the single highest-yield topic in MCAT® biochemistry.

Enzyme Kinetics: Michaelis-Menten kinetics, Km, Vmax, kcat, Lineweaver-Burk plots, competitive inhibition, noncompetitive inhibition, uncompetitive inhibition, mixed inhibition, allosteric regulation, feedback inhibition, and enzyme cofactors and coenzymes. Understand how each type of inhibition affects Km and Vmax. Enzyme kinetics connects directly to pharmacology (drug mechanisms, dose-response relationships) and is high-yield on the MCAT® and in medical school.

Metabolism (Central Pathways): Glycolysis (substrates, products, key regulatory enzymes, ATP yield), gluconeogenesis (substrates, regulation, tissue localization), glycogen metabolism (synthesis, degradation, regulation by insulin and glucagon), the citric acid cycle (substrates, products, regulatory enzymes, connections to electron transport), oxidative phosphorylation (electron transport chain complexes, chemiosmotic theory, ATP synthase, P/O ratio, inhibitors and uncouplers), the pentose phosphate pathway (NADPH production, ribose-5-phosphate), fatty acid synthesis, fatty acid beta-oxidation, ketone body metabolism, and amino acid catabolism. For each pathway, know the key regulatory steps, the inputs and outputs, and how the pathway is regulated by hormones and energy status.

Lipid Biochemistry: Fatty acid structure (saturated, unsaturated, essential), triglycerides, phospholipids, sphingolipids, cholesterol, lipoproteins (chylomicrons, VLDL, LDL, HDL), and lipid transport. Lipid biochemistry connects to cardiovascular disease risk (LDL/HDL ratios), atherosclerosis, and statin pharmacology.

Nucleic Acid Biochemistry: Nucleotide structure, DNA and RNA structure, DNA replication enzymology (helicase, primase, DNA polymerase, ligase, topoisomerase), transcription (RNA polymerase, promoters, transcription factors), translation (ribosomes, tRNA, codons, post-translational modifications), and gene regulation. These topics bridge molecular biology and biochemistry and are heavily tested.

Metabolic Integration and Regulation: How the fed state, fasting state, and starvation affect metabolic pathways. How insulin and glucagon regulate glucose and lipid metabolism. How the liver, muscle, adipose tissue, and brain use different metabolic fuels. Understanding metabolic integration is essential for clinical reasoning about diabetes, metabolic syndrome, inborn errors of metabolism, and nutritional disorders.

Free Study Resources

Khan Academy® (Free): Khan Academy® MCAT® Biochemistry collection covers amino acids, protein structure, enzyme kinetics, and central metabolic pathways. It is the best free starting point for MCAT®-level biochemistry review. See our Khan Academy® guide.

OpenStax (Free): While OpenStax does not have a dedicated biochemistry textbook, its biology and chemistry texts cover many biochemistry topics (metabolic pathways, enzyme function, nucleic acid chemistry). See our free textbooks page.

Anki Flashcard Decks (Free): Biochemistry Anki decks are among the most popular in the pre-med community. The amino acid deck alone can significantly improve your MCAT® performance. See our spaced repetition guide.

Study Strategies

Draw Metabolic Pathways from Memory: For each major pathway (glycolysis, citric acid cycle, electron transport chain, fatty acid oxidation, gluconeogenesis), practice drawing the pathway from memory, including substrates, products, enzymes, and regulatory points. Then check your drawing against your notes. This is the single most effective study method for metabolic biochemistry.

Learn Amino Acids Early and Thoroughly: If you know the amino acids cold (structures, properties, charges at physiological pH, one-letter codes), many other biochemistry topics become easier. Enzyme active sites, protein-protein interactions, and MCAT® questions about amino acid substitution effects all depend on amino acid knowledge. Invest time early to build this foundation.

Connect to Clinical Medicine: Biochemistry has more clinical connections than almost any other pre-health course. Diabetes is a disorder of glucose metabolism. Gout is a disorder of purine metabolism. Phenylketonuria is an inborn error of amino acid metabolism. Heart failure involves disrupted oxidative phosphorylation. Make these connections as you study. They improve retention and prepare you for clinical coursework.

For related guides, see our biology, general chemistry, and organic chemistry study guides. For exam-specific preparation, see our MCAT® prep guide.

Vitamins and Cofactors: Know the water-soluble vitamins (B vitamins and vitamin C) and their roles as enzyme cofactors. Thiamine (B1) is a cofactor for pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase. Riboflavin (B2) is a component of FAD. Niacin (B3) is a component of NAD+. Pyridoxine (B6) is essential for aminotransferases. Cobalamin (B12) and folate are essential for one-carbon metabolism and DNA synthesis. Vitamin deficiencies produce characteristic clinical presentations (beriberi, pellagra, scurvy, megaloblastic anemia) that are heavily tested on licensing exams.

Hormonal Regulation of Metabolism: Understand how insulin, glucagon, epinephrine, and cortisol regulate metabolic pathways. Insulin promotes glucose uptake, glycogen synthesis, fatty acid synthesis, and protein synthesis (the “fed state”). Glucagon promotes glycogenolysis, gluconeogenesis, and fatty acid oxidation (the “fasted state”). Epinephrine activates fight-or-flight metabolic responses. Cortisol supports gluconeogenesis and has anti-inflammatory effects. These hormonal regulation patterns are essential for understanding diabetes, metabolic syndrome, Cushing syndrome, and Addison disease.

Signal Transduction: G-protein coupled receptors, receptor tyrosine kinases, second messengers (cAMP, IP3, DAG, calcium), kinase cascades, and nuclear receptors. Signal transduction connects biochemistry to pharmacology (many drugs target specific receptors or signaling pathways) and to cancer biology (oncogenes and tumor suppressors often involve signaling proteins). This topic is high-yield on the MCAT® and appears throughout medical school coursework.

Acid-Base Biochemistry: The Henderson-Hasselbalch equation applied to amino acid titration curves, buffer capacity of the bicarbonate system, and the relationship between pKa and the ionization state of functional groups at physiological pH. Understanding how amino acid charge changes with pH is essential for predicting protein behavior, enzyme catalysis, and drug absorption. This topic bridges general chemistry, organic chemistry, and biochemistry and is tested frequently on the MCAT®.

Clinical Correlations by Pathway: For each major metabolic pathway, learn at least one clinically relevant disease or condition that results from a deficiency in that pathway. Pyruvate dehydrogenase deficiency causes lactic acidosis. Glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency) causes hemolytic anemia triggered by oxidative stress. Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency disrupts fatty acid oxidation. Phenylketonuria results from phenylalanine hydroxylase deficiency. These clinical correlations are heavily tested on the USMLE® and medical school exams, and learning them alongside the normal pathway makes both the normal and the pathological easier to remember.

Practice with Experimental Passages: The MCAT® biochemistry section frequently presents research-style experimental passages that describe laboratory studies of enzymes, metabolic pathways, or protein function. You are asked to interpret data, predict outcomes of experimental manipulations, and draw conclusions from graphs and tables. Practice with these passage-based questions during your preparation, not just discrete content questions. Understanding how to read and interpret a Lineweaver-Burk plot, a substrate saturation curve, or a Western blot result is a testable skill distinct from knowing the content itself.

References

Khan Academy. “MCAT Biochemistry.” Khan Academy, 2025. https://www.khanacademy.org/test-prep/mcat. Accessed March 2026.
AAMC. “MCAT Content Outline.” AAMC, 2025. https://students-residents.aamc.org/mcat-exam. Accessed March 2026.
OpenStax. “Biology 2e.” Rice University, 2025. https://openstax.org/details/books/biology-2e. Accessed March 2026.