🧬 AP® Biology Cheatsheet 2025
Comprehensive Guide: 8 Units | 80 Flashcards | 80 Quiz Questions
🧪 Unit 1: Chemistry of Life
Water Properties:
- 💧 Hydrogen bonding creates cohesion (water-water), adhesion (water-other)
- 🌡️ High specific heat & heat of vaporization (temperature regulation)
- 🧊 Less dense as solid (ice floats, insulates aquatic life)
Macromolecules:
- 🍯 Carbohydrates: monosaccharides, disaccharides, polysaccharides
- 🥑 Lipids: fats, phospholipids, steroids (energy, membranes)
- 🥩 Proteins: 20 amino acids, 4 structure levels
- 🧬 Nucleic acids: DNA/RNA, purines (A,G), pyrimidines (C,T,U)
Chemical Bonds:
- ⚡ Ionic (electron transfer), Covalent (sharing), Hydrogen (weak)
- 📊 pH scale 0-14; acids <7, bases >7, buffers resist changes
🔬 Unit 2: Cell Structure & Function
Cell Theory:
- 🔬 All life made of cells, cells = basic unit, cells from pre-existing cells
- 🦠 Prokaryotes: no nucleus (bacteria, archaea)
- 🧬 Eukaryotes: nucleus present (plants, animals, fungi, protists)
Organelles:
- 🧠 Nucleus: DNA storage, nuclear envelope with pores
- 🏭 Ribosomes: protein synthesis
- 🚚 ER: Rough (protein), Smooth (lipid synthesis, detox)
- 📦 Golgi: processing, packaging, shipping
- ⚡ Mitochondria: ATP production via respiration
- 🌱 Chloroplasts: photosynthesis (plants only)
Transport:
- 🚪 Fluid mosaic model: phospholipids + proteins
- ⬇️ Passive: diffusion, osmosis (no ATP)
- ⬆️ Active: pumps, cotransport (requires ATP)
🔋 Unit 3: Cellular Energetics
ATP & Energy:
- ⚡ ATP = adenosine + 3 phosphates, cellular energy currency
- 🔄 ATP ↔ ADP + Pi + energy
Enzymes:
- 🔗 Lower activation energy, substrate specific
- 🎯 Active site fits substrate (induced fit model)
- 🌡️ Temperature, pH, concentration affect activity
Photosynthesis:
- 🌱 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
- ☀️ Light reactions: photosystems, ATP/NADPH production
- 🔄 Calvin cycle: CO₂ fixation, glucose synthesis
Cellular Respiration:
- 🔥 C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ~32 ATP
- 1️⃣ Glycolysis: glucose → pyruvate (cytoplasm, 2 ATP)
- 2️⃣ Krebs cycle: pyruvate → CO₂ + NADH/FADH₂
- 3️⃣ Electron transport: NADH/FADH₂ → ATP
📡 Unit 4: Cell Communication & Cycle
Signal Transduction:
- 📡 Reception → Transduction → Response
- 🎯 Paracrine (local), endocrine (hormonal), autocrine (self)
- 💬 Second messengers: cAMP, IP₃, Ca²⁺
Feedback:
- ➖ Negative: maintains homeostasis (insulin/glucose)
- ➕ Positive: amplifies response (oxytocin, clotting)
Cell Cycle:
- 🔄 G₁ (growth), S (synthesis), G₂ (prep), M (mitosis)
- 🛡️ Checkpoints: G₁/S, G₂/M, spindle
Mitosis:
- 1️⃣ Prophase: chromatin condenses
- 2️⃣ Metaphase: chromosomes align
- 3️⃣ Anaphase: sister chromatids separate
- 4️⃣ Telophase: nuclei reform
👪 Unit 5: Heredity
Meiosis:
- 🧬 Diploid (2n) → haploid (n), sexual reproduction
- 1️⃣ Meiosis I: homologs separate (reduction)
- 2️⃣ Meiosis II: sister chromatids separate
- 🔀 Crossing over: recombination in prophase I
Mendelian Genetics:
- 👨🔬 Laws: segregation, independent assortment
- 🧬 Genotype (genes) vs phenotype (observable)
- 🔢 Monohybrid (3:1), dihybrid (9:3:3:1) ratios
Beyond Simple Dominance:
- 🌈 Incomplete dominance: blended phenotype
- 🩸 Codominance: both expressed (ABO blood)
- 📊 Polygenic: multiple genes affect one trait
- ♂️♀️ Sex-linked: genes on X or Y chromosomes
Abnormalities:
- ❌ Nondisjunction: improper separation
- ➕ Trisomy: extra chromosome (Down syndrome)
🧬 Unit 6: Gene Expression & Regulation
Central Dogma:
- 🧬 DNA → RNA → Protein
DNA Replication:
- 🔄 Semi-conservative: each strand = template
- ➡️ 5' to 3' direction only
- 🧰 Helicase, primase, DNA polymerase, ligase
Transcription:
- 📝 DNA → mRNA by RNA polymerase
- ✂️ RNA processing: 5' cap, 3' poly-A tail, splicing
Translation:
- 🏭 mRNA → protein at ribosomes
- 🔤 Genetic code: 64 codons, 20 amino acids
- 🚀 Start (AUG), stop (UAG, UAA, UGA)
Regulation:
- 🦠 Prokaryotes: operons (lac, trp)
- 🧬 Eukaryotes: transcription factors, enhancers
- 🎛️ Epigenetics: methylation, histone modification
🦍 Unit 7: Natural Selection & Evolution
Darwin's Theory:
- 🧬 Descent with modification from common ancestor
- 🏆 Natural selection: variation, heritability, differential reproduction
- 💪 Fitness = reproductive success
Types of Selection:
- 📈 Directional: favors one extreme
- 🎯 Stabilizing: favors average
- 📊 Disruptive: favors both extremes
Population Genetics:
- 📐 Hardy-Weinberg: p² + 2pq + q² = 1
- ⚖️ Equilibrium: no mutation, selection, migration, drift
- 🎲 Genetic drift: random changes (bottleneck, founder)
Speciation:
- 🏔️ Allopatric: geographic separation
- 🧬 Sympatric: reproductive isolation without separation
Evidence:
- 🦴 Fossils, comparative anatomy, molecular biology
- 🌳 Phylogenetic trees show evolutionary relationships
🌲 Unit 8: Ecology
Population Ecology:
- 📈 Exponential: J-curve (unlimited resources)
- 📊 Logistic: S-curve (carrying capacity)
- 🛑 Limiting factors: density-dependent/independent
Community Interactions:
- 🤝 Mutualism (+/+), Commensalism (+/0)
- 🦠 Parasitism (+/-), Predation (+/-)
- ⚡ Competition (-/-)
Ecosystem Structure:
- 🌱 Producers → Primary → Secondary/Tertiary consumers
- ⚡ 10% rule: energy transfer between levels
Biogeochemical Cycles:
- 💧 Water: evaporation, precipitation, transpiration
- 🌱 Carbon: photosynthesis, respiration, fossil fuels
- 🧪 Nitrogen: fixation, nitrification, denitrification
Biodiversity:
- 🌈 Genetic, species, ecosystem diversity
- ⚖️ More diversity = greater stability
Homeostasis:
- 🔥 Thermoregulation: endotherms vs ectotherms
- 💧 Osmoregulation: water/salt balance
💯 FRQ Success Tips
📖 Read questions carefully
⏰ Prioritize by points
🎯 Do quick questions first
✂️ Skip fluff, be direct
🔤 Label responses (a, b, c)
💪 COMMIT! No "might"
📝 Always give examples
📊 Use data to support