AP Biology Notes — All 8 Units

AP Biology covers 8 units organized around 4 Big Ideas. These notes summarize the key concepts, mechanisms, and FRQ-ready explanations for each unit — the level of depth the AP exam actually tests.

Unit 1: Chemistry of Life

Water properties (polarity, hydrogen bonds, cohesion, adhesion, high specific heat), macromolecule structure and function (carbohydrates as energy/structure, lipids as membranes/energy, proteins as enzymes/structure/transport, nucleic acids as information storage), enzyme kinetics (substrate concentration, temperature, pH, competitive vs. non-competitive inhibition).

Unit 2: Cell Structure and Function

Prokaryotic vs. eukaryotic cells, membrane structure (fluid mosaic model), membrane transport (diffusion, osmosis, facilitated diffusion, active transport, endocytosis/exocytosis), cell communication (ligand-receptor binding, signal transduction cascades, second messengers like cAMP).

Unit 3: Cellular Energetics

Photosynthesis: light-dependent reactions (chlorophyll, ETC, ATP synthesis via chemiosmosis) and Calvin cycle (carbon fixation, G3P production). Cellular respiration: glycolysis, pyruvate oxidation, Krebs cycle, oxidative phosphorylation. Net ATP yields and electron carriers (NADH, FADH2).

Unit 4: Cell Communication and Cell Cycle

Signal transduction: reception → transduction → response. Cell cycle: G1, S (DNA replication), G2, M (mitosis: PMAT). Checkpoints and cyclins. Apoptosis. Cancer as uncontrolled cell division (proto-oncogenes → oncogenes, tumor suppressors).

Unit 5: Heredity

Meiosis vs. mitosis, Mendelian genetics (dominance, segregation, independent assortment), non-Mendelian patterns (incomplete dominance, codominance, sex-linkage, polygenic traits, epistasis), chi-square analysis for genetics problems.

Unit 6: Gene Expression and Regulation

DNA structure and replication, transcription (RNA polymerase, promoters), translation (ribosomes, codons, tRNA), gene regulation (operons in prokaryotes, enhancers/silencers in eukaryotes), epigenetics, mutations and their effects.

Unit 7: Natural Selection

Hardy-Weinberg equilibrium (conditions and equation p² + 2pq + q² = 1), mechanisms of evolution (natural selection, genetic drift, gene flow, mutation, sexual selection), speciation (allopatric, sympatric), phylogenetics (cladograms, shared derived characters).

Unit 8: Ecology

Population ecology (growth models: exponential J-curve vs. logistic S-curve with carrying capacity K), community ecology (competition, predation, symbiosis, succession), ecosystem ecology (energy flow — only 10% transferred per trophic level, biogeochemical cycles), conservation biology.

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