Complete College Board CED notes for Units 1–5 • Interactive flashcards + quiz • All details included
Core Idea: The structure of biological molecules determines their function; water’s unique properties emerge from hydrogen bonding.
Polarity: Water is a polar molecule with δ− oxygen and δ+ hydrogens. Hydrogen bonds: weak, non-covalent attractions between δ+ H and δ− O of another water molecule.
Emergent properties: Cohesion (water sticks to water), Adhesion (sticks to polar surfaces), High specific heat (stabilizes temperature), High heat of vaporization (cooling via evaporation), Expansion upon freezing (ice floats), Universal solvent (dissolves polar/ionic substances).
AP Exam Connection: Predict consequences if ice sank — lakes would freeze solid, destroying aquatic life.
CHNOPS: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur — most abundant in organisms.
Dehydration synthesis: removes water to form polymer (requires energy). Hydrolysis: adds water to break polymer (releases energy).
| Macromolecule | Monomer | Key Bond | Examples / Functions |
|---|---|---|---|
| Carbohydrates | Monosaccharides | Glycosidic linkages | Starch, glycogen, cellulose (energy/structure) |
| Lipids | Fatty acids + glycerol | Ester bonds | Phospholipids (membranes), steroids, long-term energy |
| Proteins | Amino acids (20 types) | Peptide bonds | Enzymes, hemoglobin, antibodies, collagen |
| Nucleic acids | Nucleotides | Phosphodiester | DNA, RNA, ATP |
Protein structure (critical): Primary (aa sequence) → Secondary (α-helices/β-sheets via H‑bonds in backbone) → Tertiary (3D shape from R‑group interactions: H‑bonds, hydrophobic forces, disulfide bridges) → Quaternary (multiple polypeptides). Mutation in primary structure can alter tertiary shape → loss of function (e.g., sickle cell).
Core Idea: Compartmentalization allows specialized functions; membrane structure dictates selective permeability.
Prokaryotic vs. Eukaryotic: Prokaryotes lack nucleus/membrane-bound organelles; eukaryotes have both.
Key organelles: Ribosomes (protein synthesis), Rough ER (protein folding), Smooth ER (lipid synthesis/detox), Golgi (sorting/packaging), Lysosomes (digestion/apoptosis), Mitochondria (ATP synthesis – double membrane, own DNA), Chloroplasts (photosynthesis – double membrane, own DNA).
Endosymbiotic theory: Mitochondria & chloroplasts were once free-living prokaryotes engulfed. Evidence: own circular DNA, 70S ribosomes, binary fission, double membrane.
Passive transport (no ATP): diffusion, osmosis (water moves toward higher solute concentration), facilitated diffusion via channel/carrier proteins.
Active transport (requires ATP): pumps (Na⁺/K⁺ pump), endocytosis, exocytosis.
Tonicity: Hypertonic → cell shrinks (water leaves); Hypotonic → swells/lyses (animals) or turgid (plants); Isotonic → no net movement.
As cell grows, volume increases faster than surface area → low SA:V ratio. Small cells have high SA:V for efficient exchange. Benefits of compartmentalization: incompatible processes separated, local environments optimized, increased surface area (cristae, thylakoids).
Core Idea: ATP couples exergonic and endergonic reactions; enzymes lower activation energy; photosynthesis and respiration transform energy.
Activation energy (Ea): initial energy needed. Enzymes (usually proteins) lower Ea without being consumed. Induced fit model: substrate binding changes enzyme shape.
Inhibition: Competitive (binds active site, overcome by high substrate); Noncompetitive/allosteric (binds elsewhere, changes active site shape).
Factors affecting activity: temperature, pH, substrate concentration (Vmax, Km).
1st law: energy conserved, 2nd law: entropy increases. Living systems require constant energy input. Energy coupling: exergonic (ATP hydrolysis) drives endergonic reactions.
Equation: 6CO₂ + 12H₂O + Light → C₆H₁₂O₆ + 6O₂ + 6H₂O.
Light reactions (thylakoid membrane): Inputs: light, H₂O, ADP+Pi, NADP⁺ → Outputs: O₂, ATP, NADPH.
Calvin cycle (stroma): Inputs: CO₂, ATP, NADPH → Outputs: G3P (glucose precursor), ADP+Pi, NADP⁺. Carbon fixation by RuBisCO.
Overall: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ~36‑38 ATP.
Phases: Glycolysis (cytosol) → 2 pyruvate, 2 ATP, 2 NADH. Pyruvate oxidation (matrix) → 2 Acetyl‑CoA, 2 NADH, 2 CO₂. Krebs cycle (matrix) → 4 CO₂, 6 NADH, 2 FADH₂, 2 ATP. Oxidative phosphorylation (inner membrane): ETC uses NADH/FADH₂ to pump H⁺, chemiosmosis via ATP synthase → ~34 ATP. O₂ is final electron acceptor. Fermentation (no O₂): only glycolysis, 2 ATP, regenerates NAD⁺ (lactic acid or alcohol).
Core Idea: Signal transduction pathways convert extracellular signals to cellular responses; cell cycle checkpoints maintain genomic integrity.
Three stages: Reception (ligand binds receptor, e.g., GPCR, RTK) → Transduction (cascade of protein kinases, second messengers like cAMP, Ca²⁺, IP₃) → Response (gene expression, enzyme activation, apoptosis).
Amplification: one activated kinase can activate many downstream proteins, greatly magnifying signal.
Apoptosis: programmed cell death, clean, essential for development (e.g., webbing removal).
Interphase: G₁ (growth), S (DNA replication), G₂ (prep). M phase: mitosis (PMAT) + cytokinesis.
Checkpoints: G₁ (restriction point – environment, size, DNA damage; failure leads to G₀), G₂ (DNA replication fidelity), M (spindle attachment).
Cyclins & CDKs: CDK active only when bound to cyclin; complex phosphorylates targets to advance cycle.
Cancer: mutations in proto‑oncogenes (become oncogenes – gas pedal) or tumor suppressors (p53 – brake pedal).
Core Idea: Meiosis generates variation via crossing over, independent assortment, and random fertilization.
Meiosis I separates homologous chromosomes (reduction division), Meiosis II separates sister chromatids.
Sources of variation: Crossing over (Prophase I – exchange between non‑sister chromatids), Independent assortment (Metaphase I – 2²³ combinations in humans), Random fertilization (64 trillion possible zygotes).
Mendel’s laws: Segregation (alleles separate in anaphase I), Independent assortment (genes on different chromosomes segregate independently).
Punnett squares: Monohybrid (Aa × Aa → 3:1 phenotype). Dihybrid (AaBb × AaBb → 9:3:3:1 if unlinked).
Non‑Mendelian: Incomplete dominance (pink flowers), Codominance (AB blood), Sex‑linked (X‑linked recessive more common in males), Linked genes (recombination frequency indicates distance), Polygenic inheritance (continuous traits like height).
Pedigree analysis: trace autosomal dominant/recessive, X‑linked.
Nondisjunction: failure of homologous chromosomes (Meiosis I) or sister chromatids (Meiosis II) to separate → aneuploidy (e.g., Trisomy 21 – Down syndrome, Monosomy X – Turner syndrome). Mosaicism: error after fertilization affects only some cells.
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