Biology is the largest content area on the Biological and Biochemical Foundations section, and the MCAT tests it as applied reasoning about experiments rather than rote recall. This overview maps the biology you need — from the cell and its molecular machinery through genetics, evolution, and the organ systems — and points to the deeper guides for each topic.
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update Updated October 2026
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Biology is the largest content area on the Biological and Biochemical Foundations section, and the MCAT tests it as applied reasoning about experiments rather than rote recall.
check_circleBio/Biochem is roughly two-thirds introductory biology; most questions reason from a passage, figure, or experiment rather than testing isolated facts.
check_circleCell biology, molecular genetics, and physiology are the highest-yield clusters — organize your review around structure-to-function and information flow.
check_circleThe central dogma (DNA → RNA → protein) and its regulation underlie a large share of molecular questions.
check_circleOrgan-system physiology is best learned as feedback loops and how systems interact, not as memorized parts lists.
check_circlePair this with the Bio/Biochem rapid-review sheet for a last-week condensation of the whole section.
The Cell and Its Machinery
The eukaryotic cell is the organizing unit of most MCAT biology. Know the membrane-bound organelles and their jobs — nucleus, mitochondria, rough and smooth endoplasmic reticulum, Golgi, lysosomes, and peroxisomes — plus the cytoskeleton and how the plasma membrane controls transport through diffusion, facilitated diffusion, and primary and secondary active transport. The cell cycle (G1, S, G2, M) and its checkpoints, along with mitosis and meiosis, connect cell biology to genetics and to cancer.
Molecular Biology and Genetics
Molecular biology follows the central dogma: DNA is replicated semiconservatively, transcribed to RNA, processed, and translated into protein, with regulation at each step. Classical genetics adds Mendelian inheritance, pedigrees, and the patterns of dominant, recessive, and X-linked traits, while population genetics uses the Hardy-Weinberg equations to relate allele and genotype frequencies. Biotechnology tools — PCR, gel electrophoresis, cloning, and sequencing — recur in experimental passages.
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Most molecular questions reduce to one idea: where in the DNA → RNA → protein pathway did something change, and what is the downstream effect?
Evolution and Diversity
Evolution ties biology together. Natural selection acts on heritable variation, and mechanisms such as genetic drift, gene flow, mutation, and non-random mating change allele frequencies over time. Understand fitness, speciation, and the evidence for common ancestry, and be ready to reason about how selective pressures in an experiment would shift a population. A working knowledge of microbiology — viral and bacterial structure and replication — supports both evolution and immunology questions.
Organ Systems and Physiology
Physiology is tested as integrated, feedback-controlled systems. Prioritize the nervous and endocrine systems (the two control systems), the cardiovascular and respiratory systems (transport and gas exchange), and the renal and digestive systems (filtration, absorption, and homeostasis), along with the immune, musculoskeletal, and reproductive systems. For each, focus on how it maintains homeostasis and how it interacts with the others, because MCAT passages usually cross system boundaries.
Straight from the Progress Note question bank, each with a cited explanation. No account needed.
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Restriction enzymes (restriction endonucleases) are widely used in molecular biology. What do they do?
Answer: E. Restriction enzymes are bacterial endonucleases that recognize and cut DNA at specific short sequences (often palindromes), a property exploited to cut DNA at predictable sites for cloning and analysis. Joining DNA fragments (A) is done by DNA ligase, copying RNA into DNA (B) is reverse transcriptase, adding nucleotides to a growing strand (C) is DNA polymerase, and translating mRNA (D) is done by ribosomes. Cutting DNA at specific recognition sequences is the defining function of a restriction enzyme.
A study finds that neighborhood violence exposure predicts chronic stress biomarkers. Which mechanism best explains how environments influence biology?
Answer: B. Biological embedding describes how repeated environmental exposures influence physiological systems, producing durable biological changes. This concept extends beyond mere psychological priming.
A student increases recall by organizing biology terms into meaningful categories during study. Which memory process best explains this improvement?
Answer: B. Chunking groups individual items into larger, meaningful units, effectively increasing the amount of information maintained in working memory and facilitating long-term encoding.
Source: Cowan, N. (2010). The magical mystery four: How many items in working memory? Current Directions in Psychological Science, 19(1), 51–57.
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Introductory biology makes up roughly 65 percent of the Biological and Biochemical Foundations section, alongside about 25 percent biochemistry and small amounts of general and organic chemistry. Biology is therefore the single largest content area on that section.
What biology topics are highest-yield for the MCAT?expand_more
Cell biology, molecular genetics (the central dogma and its regulation), and organ-system physiology are the highest-yield clusters. Evolution and microbiology are also tested and tie the material together. Focus on reasoning about experiments and figures rather than memorizing isolated facts.
How should I study MCAT biology?expand_more
Organize review around two themes: structure-to-function and information flow. Learn physiology as feedback loops and system interactions rather than parts lists, practice interpreting experimental passages, and consolidate with the Bio/Biochem rapid-review sheet in the final weeks.
Is biochemistry separate from biology on the MCAT?expand_more
Biochemistry is scored within the same Bio/Biochem section but is treated as its own high-yield area covering amino acids, enzymes, and metabolism. Biology and biochemistry overlap heavily, so studying them together — molecular biology bridges the two — is efficient.
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