AP Biology Exam Review Plan

AP Bio Exam Review Plan

  • Download the checklist at apbiosuccess.com/checklist.
  • Use three highlighters: red, green, and yellow.
  • Stoplight method:
    • Green: Items known well.
    • Yellow: Items known a little.
    • Red: Items not known at all.
  • Prioritize studying: red -> yellow -> green.

Resources

  • Tutorials and comprehensive AP Bio reviews on learn-biology.com.
  • Unit and topic reviews on the Science Music Videos channel.
  • Live reviews (schedule and links below).

AP Bio Unit 1: Chemistry of Life

Topic 1.1: Water and Hydrogen Bonding

  • Water is polar and forms hydrogen bonds (weak intermolecular bonds).
  • Acts as the universal solvent.
  • Key properties: cohesion, adhesion, surface tension, and high specific heat.
  • Hydrogen bonds are crucial in DNA, RNA (for specific shapes), proteins, and intermolecular interactions.

Topics 1.2 to 1.3: Elements of Life

  • Molecules of life are built from monomers combining into polymers.
  • Dehydration synthesis: Combining monomers into polymers.
  • Hydrolysis: Taking polymers apart.
  • Carbohydrates:
    • Used for energy storage and structure.
    • Monosaccharides: energy storage
    • Disaccharides: energy transpor
    • Polysaccharides: energy storage (starch) and structure (cellulose in cell walls).
  • Lipids:
    • Non-polar.
    • Key unit: fatty acid (saturated or unsaturated).
    • Saturated: solid.
    • Unsaturated: liquid, with bends and kinks.
    • Functions: energy storage (fats and oils), waterproofing (waxes), membrane formation (phospholipids), and signaling (steroids).
  • Phospholipids:
    • Dual nature: hydrophobic non-polar tail and hydrophilic polar head.
    • In water, heads bond with water, tails form a water-free zone.
    • Forms a phospholipid bilayer (basis of membranes).
  • Proteins:
    • Diverse functions: motion (muscle tissue), enzymes, structure, transport, energy storage, and signaling.
    • Monomers: amino acids (amino group, carboxyl group, and R group).
    • Four levels of structure:
      • Primary: genetically determined sequence of amino acids.
      • Secondary: alpha helices and beta-pleated sheets (interactions between amino acids in the polypeptide backbone).
      • Tertiary: complex turns and loops (R groups interact via hydrogen bonds, covalent bonds, hydrophobic interactions, and ionic bonds).
      • Quaternary: aggregation of multiple polypeptide chains.
  • Nucleic acids:
    • Molecules of heredity, especially DNA.
    • RNA: information transfer (messenger RNA); can catalyze reactions (ribosomes, spliceosomes, microRNAs).
    • Nucleotides: five-carbon sugar, nitrogenous base, and phosphate group.
    • DNA vs. RNA:
      • Different sugars: deoxyribose (DNA) vs. ribose (RNA).
      • Bases: A, T, C, G (DNA) vs. A, U, C, G (RNA).
  • DNA Structure:
    • Double-stranded (double helix).
    • Two sugar-phosphate backbones.
    • Base pairing: adenine (A) with thymine (T), cytosine (C) with guanine (G).
    • Anti-parallel structure: one strand is 5' to 3', the other is 3' to 5'.

Unit 2: Cell Structure and Function

  • Prokaryotic vs. eukaryotic cells (size, structure, DNA packaging).
  • Cell geography (organelles in animal cells, plant cells).
  • Plant cell differences highlighted in bold.

Topic 2.3: Cell Size

  • Cells are small to maximize surface area to volume ratio.
  • Surface area decreases relative to volume as size increases.
  • Adaptations to increase surface area: gills, elephant ears, mitochondrial membrane folds, intestinal lining.
  • Adaptations to decrease surface area: whale size (heat retention).

Topics 2.4 to 2.9: Membrane Structure and Function

  • Selective permeability: controlling what enters and leaves the cell.
  • Phospholipid bilayer as the framework.
  • Fluid mosaic model: phospholipids, protein, and cholesterol moving around.
  • Molecules and their functions:
    • Phospholipids: membrane framework.
    • Cholesterol: fluidity buffer (stabilizes at high temperatures, maintains fluidity at low temperatures).
    • Proteins: transport, cytoskeleton attachment, membrane-embedded enzymes, signal transduction, cell-cell recognition.

Membrane Transport

  • Diffusion: movement from higher to lower concentration (passive transport).
  • Simple diffusion: small, non-polar molecules (oxygen, carbon dioxide, lipids, steroids, fats).
  • Facilitated diffusion: polar molecules and ions via protein channels.
  • Active transport: pumping molecules against their concentration gradient; requires ATP -> ADP.
  • Bulk transport:
    • Endocytosis: membrane buckles in to bring materials into the cell via vesicles.
    • Exocytosis: vesicles fuse with the membrane to dump contents outside.
  • Osmosis: diffusion of water from higher to lower concentration.
    • Water flows from hypotonic (less solute) to hypertonic (more solute).
    • Predict osmosis effects on plant and animal cells.
      • Plant cells favor hypotonic environments.
      • Animal cells (red blood cells): bursting in hypotonic conditions.
  • Water potential: formal way to describe osmosis.
    • Water potential (Ψ)=Solute potential (Ψs)+Pressure potential (Ψp)\text{Water potential (Ψ)} = \text{Solute potential (Ψs)} + \text{Pressure potential (Ψp)}
    • Adding solute decreases water potential.
    • Water flows from higher to lower water potential.
    • Adding pressure increases water potential, and water flows away from high pressure.

Topics 2.10 through 11: Cellular Compartmentalization

  • Cells have internal compartments with special pH/chemistry for different functions.
  • Endomembrane system: nuclear membrane, rough ER, smooth ER, vesicles, Golgi, lysosomes.
  • Mitochondria and chloroplasts are not part of the endomembrane system; they are endosymbionts (descendants of once-independent organisms).
  • Evidence for endosymbiosis: circular DNA, binary fission, bacteria-like ribosomes, protein synthesis, two membranes (outer membrane as a vestige).

AP Bio Unit 3: Cellular Energetics

Enzymes

  • Protein catalysts that lower activation energy.
  • Highly specific, binding to substrates at an active site.
  • Sensitive to pH/temperature changes (denaturation).
  • Denaturation: Change in active site shape, substrate can no longer interact, activity plummets.
  • Inhibition:
    • Competitive inhibition: a molecule competes with the substrate for the active site.
    • Non-competitive inhibition: a molecule binds to an allosteric site, changing the active site's shape.
  • Allosteric regulation: modulates enzyme activity.

Topic 3.4: Cell Energy

  • Metabolic pathways: linked series of enzyme-controlled reactions where the product of one reaction is the reactant for the next.
    • Linear (glycolysis) or cyclical (Krebs cycle, Calvin cycle).
  • Exergonic reactions: release energy -> drive cellular work.
  • Endergonic reactions: require energy.
  • Coupling through ATP:
    • ATP: ribose, a nitrogenous base, and three phosphate groups.
    • ADP + phosphate -> ATP (endergonic, powered by cellular respiration).
    • ATP -> ADP + phosphate (exergonic, energy for cellular work).
    • Every arm can be moved by hydrolyzing ATP (removing the third phosphate)

Topic 3.5: Photosynthesis

  • Photoautotrophs use light energy to combine carbon dioxide and water to create carbohydrates; oxygen is released.
  • Formula: 6CO<em>2+6H</em>2O+light→C<em>6H</em>12O<em>6+6O</em>26CO<em>2 + 6H</em>2O + light \rightarrow C<em>6H</em>{12}O<em>6 + 6O</em>2
  • Two phases:
    • Light reactions: light energy -> chemical energy (ATP and NADPH).
    • Calvin cycle: energy in ATP and NADPH -> carbohydrate (G3P).
The Light Reactions
  • Light powers an electrical current -> proton pumps pump protons into the thylakoid space.
  • Facilitated diffusion through ATP synthase generates ATP.
  • Photosystems: protein complexes packed with chlorophylls that convert light energy into electricity.
  • Electron transport chain: protons are pumped from the stroma to the thylakoid space.
  • Oxygen released from splitting water molecules, also creating additional protons.
  • Electron flow from one photosystem to another -> NADP+ reduced to NADPH.
In the Calvin Cycle
  • Three phases convert carbon dioxide into glyceraldehyde 3-phosphate (G3P).
    • Carbon fixation: carbon dioxide is incorporated into a six-carbon compound, then broken into a three-carbon compound.
    • Energy investment: ATP and NADPH energize the compound, forming G3P.
    • Regeneration: RuBP (five-carbon molecule) is regenerated, requiring ATP.

Topic 3.6: Cellular Respiration

  • Cells convert glucose into ATP.
    • Animals perform cellular respiration; plants do both cellular respiration and photosynthesis.
  • Four stages: glycolysis, the link reaction, the Krebs cycle, and the electron transport chain.
  • Know inputs and outputs for glycolysis, the link reaction and the Krebs cycle.
  • Oxidizing food (glucose) and creating mobile electron carriers (NADH and FADH2).
  • Electron carriers power electrical current -> proton pumps pump protons from the matrix to the intermembrane space.
  • Protons diffuse out through ATP synthase, combining ADP and phosphate into ATP.
  • Oxygen is the final electron acceptor in the electron transport chain.
Anaerobic Respiration
  • Anaerobic respiration: occurs without oxygen, generating only 2 ATPs from glycolysis.
  • Combined with fermentation, which regenerates NAD+.
  • Pyruvate (three-carbon output of glycolysis) is reduced to ethanol or lactic acid.
  • NADH is oxidized to NAD+ for glycolysis to continue.

AP Bio Unit 4: Cell Communication, Feedback, and the Cell Cycle

Cell Communication

  • Cells communicate directly (touching) or through signals.
  • Signals are ligands that bind to specific receptors.
  • Three phases:
    • Reception of the ligand.
    • Signal transduction (amplification of signal).
    • Cellular response (gene activation or enzyme activation).
  • G-protein coupled receptors.
  • Steroid hormones diffuse through the phospholipid bilayer and bind with cytoplasmic receptors, then enter the nucleus and activate genes.

Topic 4.5: Homeostasis and Feedback

  • Homeostasis: maintaining constant internal conditions.
  • Feedback: output of a system is also an input to the system.
    • Negative feedback: output quiets the system.
    • Positive feedback: output accelerates internal changes.
  • Glucose homeostasis: insulin lowers blood sugar; glucagon raises it.
    • Diabetes: breakdown in insulin production (Type 1) or cell response to insulin (Type 2).
  • Positive feedback loops:
    • Oxytocin and childbirth: baby growth -> stretch receptors -> oxytocin release -> increased contractions.
    • Fruit ripening and the gaseous hormone ethylene.

Topics 4.6 to 4.7: The Cell Cycle

  • Phases of mitosis: interphase, prophase, metaphase, anaphase, telophase, and cytokinesis.
  • Interphase: G1 (general growth), S (DNA synthesis), G2 (preparation for M phase).
  • G0 phase: cells become highly specialized, leaving the cell cycle.
  • Checkpoints: cell checks for conditions, pauses if they are not met.
  • Regulation:
    • External: signals from outside the cell.
    • Internal: cyclins and cyclin-dependent kinases.
  • Cancer: unregulated cell division.
    • Mutations cause cells to grow in one location, forming a tumor.
    • Metastasis = spread of cancer to other sites.
    • Proto-oncogenes increase the rate of the cell division by either acting as the accelerator or mutating or removing the cell division inhibitors. Tumor suppressor genes undermine the checkpoint.

AP Bio Unit 5: Heredity

Meiosis

  • Diploid germ cells -> haploid sperm and egg cells.
  • Meiosis begins with DNA replication -> diploid cells with doubled chromosomes.
  • Meiosis I: homologous pairs are separated.
  • Meiosis II: sister chromatids are pulled apart.
  • Phases are the same as mitosis but doubled.
  • Prophase I: homologous pairs pair up and exchange DNA (crossing over).
  • Independent assortment occurs during metaphase I.
  • Four haploid gametes result.
  • Sexual reproduction generates diversity through:
    • Independent assortment.
    • Crossing over and genetic recombination.
    • Fertilization (combining genomes).
  • Mitosis results in clones of the parent cell.
  • Sex determination:
    • Mammals: XX/XY system.
    • Birds: ZW/ZZ system.
    • Reptiles: temperature.
    • Bees/wasps: males are haploid, females are diploid.
  • Nondisjunction: homologous pairs or sister chromatids don't separate correctly.
    • Trisomy: three chromosomes instead of a homologous pair (Down syndrome).
    • Monosomy: one chromosome instead of a pair (Turner syndrome, only survivable in the sex chromosomes).

Topics 5.3 to 5.5: Genetics

  • Gene: basic unit of heredity; sequence of nucleotides coding for RNA or protein.
  • Key concepts:
    • Mendel's principle of segregation of alleles.
    • Homozygous vs. heterozygous.
    • Dominant vs. recessive.
    • Genotype vs. phenotype.
  • Monohybrid crosses: cross between two heterozygotes -> 3:1 phenotypic ratio, 1:2:1 genotypic ratio.
  • Sex-linked genes: genes on the X chromosome.
    • Passed on by the mother.
    • Males either have the allele or they don't.
  • Independent assortment: two gene pairs -> 9:3:3:1 phenotypic ratio.
  • Linked genes: genes on the same chromosome that are mostly inherited together.
    • Can be separated by crossing over.
    • Recombination frequencies -> chromosome maps showing distance between alleles.
  • Non-nuclear inheritance: genes on mitochondria.
  • Incomplete dominance: blending effect between alleles.
  • Genotype-environment interaction: environment determines phenotype.
  • Chi-square: analyze results of genetic crosses.

AP Bio Unit 6: Gene Expression

Topic 6.2: DNA Replication

  • Semiconservative: original strand separates, each strand serves as a template; daughter strands are half new and half old.
  • Enzymes: helicase, DNA polymerase, primase, ligase.
  • DNA polymerase synthesizes in the 5' to 3' direction.
  • Leading strand: continuous replication.
  • Lagging strand: fragmentary (Okazaki fragments) sealed together.

Topic 6.3: Transcription

  • Making RNA from a DNA template.
  • Ability to translate any sequence of RNA into amino acids using a genetic code dictionary.
  • Details of protein synthesis itself.

Topics 6.5 to 6.6: Gene Regulation

  • Operons: gene regulation systems in prokaryotes.
  • Multicellular eukaryotes: all cells in the same organism are genomically equivalent but express different genes.
  • Acetylation turns genes on; methylation turns genes off.
  • Epigenetics: changes in DNA expression involving reversible chemical modifications or changes in DNA packaging.
  • Eukaryotic genes have introns -> alternative splicing of exons.
    • Exons: expressed sequences that are translated into proteins.
    • Introns: intervening sequences that get edited out.

Topic 6.7: Mutation

  • Point mutations: one nucleotide changes to another.
    • Effects: none (redundancy), nonsense (stop codon inserted), missense (amino acid changes).
  • Frameshift mutations: change the reading frame.
  • Mutations can be positive, negative, or neutral.
  • Mutations are the source of variation that makes evolution possible.
  • Horizontal gene transfer: one individual transmits genes to another of the same generation.
    • Conjugation in bacteria, transformation, transduction (viruses), viral recombination.
  • Genetic Engineering and Biotechnology Techniques: PCR (amplifying DNA); restriction enzymes and gel electrophoresis (analyzing DNA); recombinant DNA and engineering plasmids (human genes into bacteria to produce gene products like insulin); and DNA sequencing.

Unit 7: Evolution

Natural Selection

  • Natural selection: adaptations through survival of the fittest.
  • Artificial selection: humans select favored traits.
  • Sexual selection: selection for reproductive advantage.
  • Effects of selection:
    • Directional selection: population's mean is pushed in one direction.
    • Stabilizing selection: against the extremes.
    • Disruptive selection: against the mean.

Topics 7.4 to 7.5: Population Genetics

  • Study of how allele frequencies change in gene pools.
  • Dominant alleles are not necessarily more common or grow in frequency over time.
  • Hardy-Weinberg equations:
    • p+q=1p + q = 1
    • p2+2pq+q2=1p^2 + 2pq + q^2 = 1
  • pp = frequency of the dominant allele; qq = frequency of the recessive allele.
  • Hardy-Weinberg principle: allele frequencies stay constant unless conditions are not met.
  • Conditions for non-evolving population:
    • Infinitely large.
    • No harmful or beneficial alleles.
    • Random mating.
    • No immigration or emigration.
    • No net mutation of one allele to another.
  • Factors causing evolution:
    • Genetic drift (random change in small populations).
    • Natural selection (some alleles harmful, some beneficial).
    • Sexual selection (some phenotypes more attractive).
    • Gene flow (genes move from one population to another).
    • Directional mutation (one allele mutates into another).
  • Evidence for evolution: fossils, homologous features, vestigial features, molecular homologies, and observed evolution.
  • Phylogeny: evolutionary history shown through branching diagrams.
    • Clade: group of organisms derived from a common ancestor.
    • Nodes, shared derived features, ancestral features, outgroups, and molecular clocks.

Topics 7.10 to 7.12: Speciation, Variation, and Extinction

  • Biological species concept: organisms that can interbreed naturally to produce fertile offspring.
  • Reproductive isolating mechanisms:
    • Prezygotic barriers: keep a zygote from forming (behavioral barriers).
    • Postzygotic barriers: zygote cannot develop or is not fertile.
  • Types of speciation:
    • Allopatric speciation: geographic barrier causing differentiation.
    • Sympatric speciation: no barrier (chromosomal changes particularly in plants caused by an error in meiosis).
  • Mass extinctions: geological or astronomical factors cause mass die-offs.
    • Cause vast decreases in biodiversity but subsequent adaptive radiation reestablishes biodiversity.

Topic 7.13: The Origin of Life

  • How did life naturally emerge in the absence of life after the Earth became habitable?
  • Geological and chemical processes led to abiotic synthesis of monomers (amino acids, monosaccharides, nucleotides).
  • Monomers -> polymers (RNA, nucleic acids, proteins).
  • Polymers become encapsulated within a membrane -> protocell.
  • Protocell becomes something that can reproduce itself, the last universal common ancestor, the last universal common ancestor (LUCA), which gives rise to the three domains of life.
  • Miller-Urey experiment (1950s): abiotic synthesis of amino acids.
  • RNA world: RNA was probably the first genetic molecule because it's informational and catalytic.
  • Inorganic precursors + RNA monomers -> RNA polymers -> complex shapes -> self-replication -> protocells -> LUCA.

AP Bio Unit 8: Ecology

Topic 8.1: Responses to the Environment

  • Case studies on learn-biology.com.
  • Learn to be analytical and carefully read the question.

Topic 8.2: Energy Flow

  • Metabolic rate and size relationship.
  • Energy flow through food webs (trophic levels).
  • Pyramid of energy: 10% of the energy is passed from trophic level to trophic level.
  • Ecological pyramids, including the pyramid of numbers.

Topics 8.3 and 8.4: Population Growth

  • Exponential growth model and logistic model.
  • Carrying capacity.
  • Biotic potential: how fast a population can grow.
  • Limiting factors: keep a population at or below its carrying capacity (density-dependent or density-independent).

Topic 8.5: Species Interactions

  • Interaction effects on two interacting species (positive, negative, or neutral).
  • Interactions and evolutionary consequences:
    • Competition -> character displacement and niche partitioning.
    • Predation, herbivory, parasitism, parasitoidism -> evolutionary arms races.
  • Keystone species control herbivores and increase biodiversity.
  • Biodiversity includes species richness (number of species) and species evenness (how evenly spread species are).
  • Simpson's diversity index.
  • Human impacts decrease diversity:
    • Destruction of habitat, habitat fragmentation.
    • Introduction of invasive species.
    • Destructive exploitation of resources.
    • Extinction vortex: populations get smaller -> genetic drift and inbreeding -> less fit -> less reproduction, more mortality -> smaller population.
    • Human activities reduce variation.