🧬 AP Biology Complete Cheatsheet 2026
Everything You Need to Know for AP Biology Success
All 8 Units • Essential Formulas • Exam Strategies • FRQ Tips
🧪 Unit 1: Chemistry of Life 8-11%
💧 Water Properties
Hydrogen Bonds: Give water special properties
Cohesion: Water molecules stick to each other
Adhesion: Water molecules stick to other surfaces
Surface Tension: Allows insects to walk on water
🧬 Macromolecules
DNA/RNA: Made of nucleic acids, store genetic information
Nucleotides: Ribose/deoxyribose + phosphate + nitrogenous base
Proteins: Made of amino acids; sequence → structure & function
Carbohydrates: Sugar monomers; store energy
Lipids: Nonpolar, found in cell membranes
⚗️ Chemical Reactions
Hydrolysis: Cleaves monomer bonds with water
Dehydration Synthesis: Forms bonds by removing water
👷 Unit 2: Cell Structure & Function 10-13%
🏭 Organelles
Ribosomes: Make proteins
ER: Detoxifies, makes lipids
Golgi Complex: Folds and packages proteins
Mitochondria: Powerhouse of cell
Lysosomes: Expels waste
📏 Cell Size
Surface Area to Volume: High SA:V ratio ideal for cells
Inner Membrane Folds: Increase SA for more ATP
🚪 Cell Transport
Phospholipid Bilayer: Selective permeability
Small Nonpolar: N₂, O₂, CO₂ pass easily
Passive Transport: High→low conc. without ATP
Active Transport: Low→high conc. with ATP
🔬 Cell Theory
Endosymbiosis Theory: Organelles merged to form new species
🔋 Unit 3: Cellular Energetics 12-16%
🧪 Enzymes
Function: Lower activation energy
Active Site: Where enzymes meet substrates
Optimal Conditions: Specific pH, temperature
Inhibitors: Competitive (compete for site) & noncompetitive (change shape)
🌱 Photosynthesis
Light Reactions: Chlorophylls charge electrons in photosystems I & II
Calvin Cycle: Powers carbohydrate production in stroma
⚡ Cellular Respiration
Process: Electron transfer → proton gradient → ATP
Oxygen Required: Aerobic process
Fermentation: Anaerobic alternative
🦠 Unit 4: Cell Communication & Cell Cycle 10-15%
📡 Cell Signaling
Paracrine: Signals nearby cells
Endocrine: Signals long distances
Autocrine: Signals within own cell
🔄 Signal Transduction
Reception: Ligand binds to receptor
Transduction: Signal amplifies with messengers
Response: Gene transcription activates
🔁 Feedback Systems
Negative: Reduces stimulus (insulin & glucose)
Positive: Increases response (oxytocin & birth)
🔄 Cell Division
Interphase: G₁, S, G₂ phases
Mitosis: Diploid → identical daughter cells
Meiosis: Diploid → haploid gametes
Genetic Diversity: Crossing over & independent assortment
👪 Unit 5: Heredity 8-11%
🧬 Basic Genetics
Genotype: Genetic makeup
Phenotype: Observable appearance
Crosses: Mono/dihybrid predict inheritance
📊 Inheritance Patterns
Autosomal: Non-sex chromosome genes
Sex-linked: Genes on X or Y chromosomes
Pedigrees: Track traits across generations
🌍 Environmental Effects
Phenotype Variation: Weight, melanin, fur color affected by environment
⚠️ Genetic Disorders
Causes: Mutated alleles, nondisjunction
🧬 Unit 6: Gene Expression & Regulation 12-16%
🔄 DNA Replication
Direction: 5' to 3'
Method: Semi-conservative
Helicase: Unwinds DNA
DNA Polymerase: Builds DNA
Ligase: Joins fragments
📝 Transcription
Process: DNA → RNA
Processing: GTP cap, poly-A tail, intron splicing
🏭 Translation
Process: Ribosome reads mRNA → protein
🎛️ Gene Regulation
Eukaryotes: Transcription factors
Prokaryotes: Operons
🧪 Biotechnology
Gel Electrophoresis: Separates DNA by size
PCR: Amplifies DNA segments
Transformation: Introduces DNA to bacteria
🦍 Unit 7: Natural Selection 13-20%
🌱 Evolution
Fitness: Reproductive success
Natural Selection: Competition + selective pressure
Random Events: Mutations & genetic drift
📊 Population Genetics
Hardy-Weinberg: Predicts equilibrium frequencies
🌳 Phylogeny
Common Ancestry: Links organisms
Phylogenetic Trees: Show relationships
Cladograms: Evolutionary diagrams
🦋 Speciation
Extinction: Creates available niches
Variation: Affects population dynamics
🌲 Unit 8: Ecology 10-15%
⚖️ Homeostasis
Definition: Maintain internal equilibrium
Energy Balance: Net gain = growth
🌡️ Thermoregulation
Endotherms: Use metabolic heat
Ectotherms: Rely on external heat
📈 Population Dynamics
Limiting Factors: Control population growth
Growth Curves: S-shaped (logistic) curves
🌿 Biodiversity
Simpson's Index: Calculates diversity
Resilience: More diversity = more resilient
🔗 Species Interactions
Types: Commensalism, mutualism, parasitism, predation, competition
⚡ Energy Flow
10% Rule: Only 10% energy transferred up trophic levels
Heat Loss: Most energy lost as heat
📐 Essential AP Biology Formulas
🧬 Hardy-Weinberg Equations
Equilibrium Equation:
p² + 2pq + q² = 1
p = frequency of dominant allele, q = frequency of recessive allele
Allele Frequency:
p + q = 1
📈 Population Growth
Population Growth Rate:
dN/dt = B - D
N = population size, B = birth rate, D = death rate
Exponential Growth:
dN/dt = rmax × N
Logistic Growth:
dN/dt = rmax × N × (K-N)/K
K = carrying capacity, rmax = maximum per capita growth rate
🌿 Simpson's Diversity Index
Diversity Formula:
D = 1 - Σ(n/N)²
n = individuals of each species, N = total individuals
Values closer to 1 = higher diversity, closer to 0 = lower diversity
Values closer to 1 = higher diversity, closer to 0 = lower diversity
💧 Water Potential
Water Potential:
Ψ = ΨP + ΨS
Solute Potential:
ΨS = -iCRT
i = ionization constant, C = molar concentration, R = pressure constant, T = temperature (K)
📊 Chi-Square Test
Chi-Square:
χ² = Σ[(observed - expected)²/expected]
Use to test for significant deviation from expected results
📏 Surface Area and Volume
Sphere Volume:
V = (4/3)πr³
Sphere Surface Area:
SA = 4πr²
Rectangular Solid Volume:
V = lwh
📝 AP Biology Exam Format
Total Time: 3 hours (Hybrid Digital Exam)
Section I: Multiple Choice
60 questions
90 minutes (1.5 hours)
50% of exam score
Mix of discrete and stimulus-based questions
Data interpretation and concept application
Section II: Free Response
6 total questions
90 minutes (1.5 hours)
50% of exam score
2 long questions (8-10 points each)
4 short questions (4 points each)
FRQ Question Types
Experimental Design/Data Analysis
Scientific Investigation
Conceptual Analysis
Model/Visual Analysis
Data Analysis with Graphing
💡 FRQ Success Tips
Read the question carefully (directions matter!)
Figure out point values and prioritize accordingly
Answer identify/graph/draw questions first (quickest)
Skip fluff, go straight to the point
Label your responses clearly (a, b, c, ...)
COMMIT to your answer - avoid "might," "possible," "I think"
Always give specific examples when possible
Use C-E-R method: Claim, Evidence, Reasoning