The MCAT Bio/Biochem Textbook

Everything the Biological and Biochemical Foundations of Living Systems section actually tests — the molecules, the systems, and how AAMC turns them into questions

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The one thing to internalize

Bio/Biochem is an experiment-and-mechanism test, not a trivia test. A large share of questions are wrapped in a research passage — a figure, a table, a described protocol — and ask you to interpret data, predict what a manipulation does, or identify the controlled variable. Knowing the biology is the entry fee; reasoning over an unfamiliar experiment is the score. Two anchors make most of FC1 tractable: know all 20 amino acids and their properties cold (they're the alphabet of half the section), and know the metabolic map well enough to say what each pathway makes, costs, and is regulated by.

A quieter fact: like Psych/Soc, a meaningful slice of these questions are really research-methods and stats in biology clothing — controls, variables, what a result would support or weaken. Fluency in reading study designs turns slow passages into fast ones.

The Bio/Biochem section at a glance

Section name	Biological and Biochemical Foundations of Living Systems
Questions	59 (mix of passage-based and discrete)
Time	95 minutes
Score range	118–132 (part of the 472–528 total)
Draws on	Introductory biology ~65%, biochemistry ~25%, general chemistry ~5%, organic chemistry ~5%

The section is built from three foundational concepts (numbered 1–3), weighted as follows. The weighting is your highest-level study-priority map — spend time in proportion to it:

Foundational concept	Theme	Exam weight
FC1	Biomolecules and the chemistry of life	55%
FC2	Cells, microbes, and how they organize and divide	20%
FC3	Organ systems and homeostasis	25%

FC1 is the single heaviest concept in this section (55%) — and it's mostly biochemistry — which is why this textbook builds out 1A first as its template.

How to study Bio/Biochem (section-specific tactics)

The plan lives in the Study Plan Playbook. This adds only the tactics specific to this content:

Mechanisms over memorization. Don't just learn that an enzyme is inhibited — learn how the inhibitor changes Km and Vmax, because that's the data the passage will hand you.
Master the amino acids early. All 20: one-/three-letter codes, side-chain class, charge at physiological pH, and the special ones (Gly, Pro, Cys, His, the aromatics). They recur in protein structure, enzymes, and metabolism.
Build one metabolic map. Glycolysis → PDH → citric-acid cycle → oxidative phosphorylation, plus the storage/breakdown branches. Know each pathway's inputs, outputs, location, and regulatory enzyme.
Read graphs and experiments out loud. Practice naming the axes, the control, and "what would happen if…" — that's the question stem in disguise.
Biochem is shared ground. The FC1 material is tested in Chem/Phys too. Learn it once, thoroughly.
Lab techniques are cheap points. Electrophoresis, chromatography, blotting, and PCR show up often and are pure recognition once you know what each separates by.

The chapters

FC1 — Biomolecules and the chemistry of life

55% of section

1A Structure and function of proteins and their constituent amino acids Proteins are polymers of amino acids. The 20 amino acids' side chains determine how a chain folds into a 3-D shape, and that shape determines function — most visibly in enzymes, the catalysts that run nearly every reaction in the cell. This category covers amino-acid chemistry, the four levels of protein structure, enzyme catalysis and kinetics, and how proteins are purified and analyzed in the lab. 1B Transmission of genetic information from the gene to the protein The central dogma: DNA is copied (replication), read into RNA (transcription), and decoded into protein (translation). This category covers the structure of nucleic acids, each step of that flow and the machinery that runs it, how cells turn genes on and off, and the lab tools (PCR, sequencing, cloning) built on these mechanisms. 1C Transmission of heritable information and genetic diversity How traits pass from parents to offspring (Mendelian genetics) and how meiosis, crossing over, and mutation shuffle the deck so offspring aren't clones. Scales up to population genetics — how allele frequencies and evolution play out across a whole population. 1D Principles of bioenergetics and fuel molecule metabolism How cells extract energy from fuel. The thermodynamics of ATP and redox, then the central pathway — glycolysis → pyruvate oxidation → citric acid cycle → oxidative phosphorylation — plus the storage/synthesis branches and the hormones that switch them on and off.

FC2 — Cells, microbes, and how they organize and divide

20% of section

2A Assemblies of molecules, cells, and groups of cells The plasma membrane defines the cell — it controls what enters and leaves — and the membrane-bound organelles inside divide the eukaryotic cell into specialized compartments. This category covers membrane structure and transport, the organelles and what each does, the cytoskeleton that gives the cell shape and movement, and how cells join into tissues. 2B The structure, growth, physiology, and genetics of prokaryotes and viruses Prokaryotes (bacteria and archaea) are single cells with no nucleus or membrane-bound organelles; viruses are not cells at all — they're packets of nucleic acid in a protein coat that can only reproduce inside a host. This category covers prokaryotic structure, growth, and gene transfer, then viral structure and life cycles. 2C Processes of cell division, differentiation, and specialization One cell becomes many through the cell cycle and mitosis, and those identical cells become different through differentiation — guided by signals, regulated gene expression, and programmed cell death (apoptosis). This category covers the cell cycle and its control, mitosis, how cells specialize, and the stages of early development.

FC3 — Organ systems and homeostasis

25% of section

3A Structure and function of the nervous and endocrine systems The body's two control systems coordinate everything else. The nervous system sends fast, targeted electrical signals; the endocrine system sends slower, longer-lasting chemical signals (hormones) through the blood. This category covers neuron structure, the action potential and the synapse, and how hormones are made, classified, and regulated. 3B Structure and integrative functions of the main organ systems The organ systems work together to keep the body's internal environment stable. This category walks through them — circulatory, respiratory, immune, lymphatic, digestive, excretory, muscular, skeletal, reproductive, and the skin — focusing on each system's structure, its core function, and how it contributes to homeostasis.

About this textbook

What this textbook is

The Study Plan Playbook is about the plan — how to sequence your prep, read your scores, and know when you're ready. This textbook is the other half: it teaches the content of the Bio/Biochem section — the actual biology and biochemistry you're tested on.

It's built around one organizing fact: Bio/Biochem is the broadest, most integrative section on the MCAT, and it rewards understanding mechanisms — not memorizing isolated facts. More than half of the section (Foundational Concept 1, 55%) is molecular: amino acids, proteins, enzymes, nucleic acids, and metabolism. The rest builds up from cells to organ systems. Questions rarely ask you to recite a definition; they hand you an experiment, a graph, or an unfamiliar pathway and ask you to reason about it. So every concept below is taught at two depths and tagged with how AAMC tests it, so you train application, not just recall.

How to read it

Every piece of content is a node with two depth levels and a few badges:

Short — the glance/cram version (a concept's one-liner). Read the Short lines top-to-bottom and you have the "condensed doc" experience.
Expanded — the full narrative treatment, for first-time learning and nuance.
Badges — quick tags on each node: what discipline it draws on (bio / biochem / gen chem / orgo), how high-yield it is, what type of thing it is (term, theory, process, distinction), and a trap flag on the notorious confusions.
How AAMC tests it / Don't confuse / Related — the application layer, the reliable distractor pairs, and cross-links to related nodes.

Read a category once at Expanded depth for understanding, then review off the Short lines and the trap nodes.

How to use it alongside your other resources

This textbook maps one-to-one to the AAMC content outline (see the spine), the same skeleton used by the popular community resources. Use it as your primary read-through and concept reference; use a flashcard deck for daily spaced repetition (amino acids and metabolism especially); use AAMC and third-party question banks to practice the application layer. Note that biochemistry overlaps both science sections — the amino-acid, enzyme, and metabolism content here is also tested in Chem/Phys, so learn it once and bank the points twice.