๐งฌ APยฎ Biology Cheatsheet 2025
Comprehensive Guide: 8 Units | 80 Flashcards | 80 Quiz Questions
๐งช Unit 1: Chemistry of Life
Water Properties:
- ๐ง Hydrogen bonding creates cohesion (water-water), adhesion (water-other)
- ๐ก๏ธ High specific heat & heat of vaporization (temperature regulation)
- ๐ง Less dense as solid (ice floats, insulates aquatic life)
Macromolecules:
- ๐ฏ Carbohydrates: monosaccharides, disaccharides, polysaccharides
- ๐ฅ Lipids: fats, phospholipids, steroids (energy, membranes)
- ๐ฅฉ Proteins: 20 amino acids, 4 structure levels
- ๐งฌ Nucleic acids: DNA/RNA, purines (A,G), pyrimidines (C,T,U)
Chemical Bonds:
- โก Ionic (electron transfer), Covalent (sharing), Hydrogen (weak)
- ๐ pH scale 0-14; acids <7, bases >7, buffers resist changes
๐ฌ Unit 2: Cell Structure & Function
Cell Theory:
- ๐ฌ All life made of cells, cells = basic unit, cells from pre-existing cells
- ๐ฆ Prokaryotes: no nucleus (bacteria, archaea)
- ๐งฌ Eukaryotes: nucleus present (plants, animals, fungi, protists)
Organelles:
- ๐ง Nucleus: DNA storage, nuclear envelope with pores
- ๐ญ Ribosomes: protein synthesis
- ๐ ER: Rough (protein), Smooth (lipid synthesis, detox)
- ๐ฆ Golgi: processing, packaging, shipping
- โก Mitochondria: ATP production via respiration
- ๐ฑ Chloroplasts: photosynthesis (plants only)
Transport:
- ๐ช Fluid mosaic model: phospholipids + proteins
- โฌ๏ธ Passive: diffusion, osmosis (no ATP)
- โฌ๏ธ Active: pumps, cotransport (requires ATP)
๐ Unit 3: Cellular Energetics
ATP & Energy:
- โก ATP = adenosine + 3 phosphates, cellular energy currency
- ๐ ATP โ ADP + Pi + energy
Enzymes:
- ๐ Lower activation energy, substrate specific
- ๐ฏ Active site fits substrate (induced fit model)
- ๐ก๏ธ Temperature, pH, concentration affect activity
Photosynthesis:
- ๐ฑ 6COโ + 6HโO + light โ CโHโโOโ + 6Oโ
- โ๏ธ Light reactions: photosystems, ATP/NADPH production
- ๐ Calvin cycle: COโ fixation, glucose synthesis
Cellular Respiration:
- ๐ฅ CโHโโOโ + 6Oโ โ 6COโ + 6HโO + ~32 ATP
- 1๏ธโฃ Glycolysis: glucose โ pyruvate (cytoplasm, 2 ATP)
- 2๏ธโฃ Krebs cycle: pyruvate โ COโ + NADH/FADHโ
- 3๏ธโฃ Electron transport: NADH/FADHโ โ ATP
๐ก Unit 4: Cell Communication & Cycle
Signal Transduction:
- ๐ก Reception โ Transduction โ Response
- ๐ฏ Paracrine (local), endocrine (hormonal), autocrine (self)
- ๐ฌ Second messengers: cAMP, IPโ, Caยฒโบ
Feedback:
- โ Negative: maintains homeostasis (insulin/glucose)
- โ Positive: amplifies response (oxytocin, clotting)
Cell Cycle:
- ๐ Gโ (growth), S (synthesis), Gโ (prep), M (mitosis)
- ๐ก๏ธ Checkpoints: Gโ/S, Gโ/M, spindle
Mitosis:
- 1๏ธโฃ Prophase: chromatin condenses
- 2๏ธโฃ Metaphase: chromosomes align
- 3๏ธโฃ Anaphase: sister chromatids separate
- 4๏ธโฃ Telophase: nuclei reform
๐ช Unit 5: Heredity
Meiosis:
- ๐งฌ Diploid (2n) โ haploid (n), sexual reproduction
- 1๏ธโฃ Meiosis I: homologs separate (reduction)
- 2๏ธโฃ Meiosis II: sister chromatids separate
- ๐ Crossing over: recombination in prophase I
Mendelian Genetics:
- ๐จโ๐ฌ Laws: segregation, independent assortment
- ๐งฌ Genotype (genes) vs phenotype (observable)
- ๐ข Monohybrid (3:1), dihybrid (9:3:3:1) ratios
Beyond Simple Dominance:
- ๐ Incomplete dominance: blended phenotype
- ๐ฉธ Codominance: both expressed (ABO blood)
- ๐ Polygenic: multiple genes affect one trait
- โ๏ธโ๏ธ Sex-linked: genes on X or Y chromosomes
Abnormalities:
- โ Nondisjunction: improper separation
- โ Trisomy: extra chromosome (Down syndrome)
๐งฌ Unit 6: Gene Expression & Regulation
Central Dogma:
- ๐งฌ DNA โ RNA โ Protein
DNA Replication:
- ๐ Semi-conservative: each strand = template
- โก๏ธ 5' to 3' direction only
- ๐งฐ Helicase, primase, DNA polymerase, ligase
Transcription:
- ๐ DNA โ mRNA by RNA polymerase
- โ๏ธ RNA processing: 5' cap, 3' poly-A tail, splicing
Translation:
- ๐ญ mRNA โ protein at ribosomes
- ๐ค Genetic code: 64 codons, 20 amino acids
- ๐ Start (AUG), stop (UAG, UAA, UGA)
Regulation:
- ๐ฆ Prokaryotes: operons (lac, trp)
- ๐งฌ Eukaryotes: transcription factors, enhancers
- ๐๏ธ Epigenetics: methylation, histone modification
๐ฆ Unit 7: Natural Selection & Evolution
Darwin's Theory:
- ๐งฌ Descent with modification from common ancestor
- ๐ Natural selection: variation, heritability, differential reproduction
- ๐ช Fitness = reproductive success
Types of Selection:
- ๐ Directional: favors one extreme
- ๐ฏ Stabilizing: favors average
- ๐ Disruptive: favors both extremes
Population Genetics:
- ๐ Hardy-Weinberg: pยฒ + 2pq + qยฒ = 1
- โ๏ธ Equilibrium: no mutation, selection, migration, drift
- ๐ฒ Genetic drift: random changes (bottleneck, founder)
Speciation:
- ๐๏ธ Allopatric: geographic separation
- ๐งฌ Sympatric: reproductive isolation without separation
Evidence:
- ๐ฆด Fossils, comparative anatomy, molecular biology
- ๐ณ Phylogenetic trees show evolutionary relationships
๐ฒ Unit 8: Ecology
Population Ecology:
- ๐ Exponential: J-curve (unlimited resources)
- ๐ Logistic: S-curve (carrying capacity)
- ๐ Limiting factors: density-dependent/independent
Community Interactions:
- ๐ค Mutualism (+/+), Commensalism (+/0)
- ๐ฆ Parasitism (+/-), Predation (+/-)
- โก Competition (-/-)
Ecosystem Structure:
- ๐ฑ Producers โ Primary โ Secondary/Tertiary consumers
- โก 10% rule: energy transfer between levels
Biogeochemical Cycles:
- ๐ง Water: evaporation, precipitation, transpiration
- ๐ฑ Carbon: photosynthesis, respiration, fossil fuels
- ๐งช Nitrogen: fixation, nitrification, denitrification
Biodiversity:
- ๐ Genetic, species, ecosystem diversity
- โ๏ธ More diversity = greater stability
Homeostasis:
- ๐ฅ Thermoregulation: endotherms vs ectotherms
- ๐ง Osmoregulation: water/salt balance
๐ฏ FRQ Success Tips
๐ Read questions carefully
โฐ Prioritize by points
๐ฏ Do quick questions first
โ๏ธ Skip fluff, be direct
๐ค Label responses (a, b, c)
๐ช COMMIT! No "might"
๐ Always give examples
๐ Use data to support