AP Biology Exam Review Plan
AP Biology Exam Review Plan
Download checklist at APBiosuccess.com/checklist
Use three highlighters:
Green: Topics known well.
Yellow: Topics known a little.
Red: Topics not known at all.
Prioritize studying:
Red items first.
Yellow items second.
Green items last (to keep topics fresh).
AP Biology Unit 1: Chemistry of Life
1.1 Water and Hydrogen Bonding
Water:
Polar molecule.
Forms hydrogen bonds (weak intermolecular bonds).
Acts as the universal solvent due to polarity and hydrogen bonding.
Key properties: cohesion, adhesion, surface tension, high specific heat.
Hydrogen bonding:
Present in DNA, RNA (forming specific shapes), proteins & intermolecular interactions.
1.2-1.3 Elements of Life
Molecules of life: built from monomers combining into polymers.
Monomers combine into polymers through dehydration synthesis.
Polymers are broken apart through hydrolysis.
Carbohydrates:
Used for energy storage and create key structures.
Monosaccharides: for energy storage.
Disaccharides: for energy transport.
Polysaccharides: store energy (starch) or make structures (cellulose in cell walls).
Lipids:
Nonpolar; key unit is the fatty acid (saturated or unsaturated).
Saturated fatty acids: more solid.
Unsaturated fatty acids: bends and kinks, more liquid.
Functions: energy storage (fats and oils), waterproofing (waxes), membrane formation (phospholipids), signaling (steroids).
Phospholipids:
Dual nature:
Hydrophobic, nonpolar tail.
Hydrophilic polar head.
In water, heads bond with water while tails form a water-free zone, creating a phospholipid bilayer (basis of membranes).
Proteins:
Diverse functions: motion (muscle tissue), structure, transport, energy storage, signaling.
Composed of amino acids (monomers):
Amino group, carboxyl group, and a variable R group (side chain).
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 group interactions via hydrogen bonds, covalent bonds, hydrophobic interactions, and ionic bonds).
Quaternary: aggregation of multiple polypeptide chains.
Nucleic Acids:
Molecules of heredity
DNA: primary hereditary role in cells.
RNA: information transfer molecule (messenger RNA).
RNA can catalyze reactions (ribosomes, spliceosomes, microRNAs).
Nucleic acid monomers are nucleotides:
Five-carbon sugar, nitrogenous base, phosphate group.
DNA vs. RNA:
Different sugar (deoxyribose vs. ribose).
Different bases (A, T, C, G in DNA; A, U, C, G in RNA).
DNA structure:
Double-stranded (double helix).
Two sugar-phosphate backbones.
Base pairing: Adenine (A) bonds with Thymine (T), Cytosine (C) bonds with Guanine (G).
Antiparallel structure: one strand runs 5' to 3', the other 3' to 5'.
Unit 2: Cell Structure and Function
Prokaryotic vs. eukaryotic cells:
Difference in size, structure & DNA packaging.
Cell Biology & Geography
Animal Cells & Plant Cells
Cell Size:
Optimized for surface area to volume ratio.
Increased surface area: gills, elephant ears, mitochondrial membrane folds, intestinal lining.
Decreased surface area: whale size (heat retention).
2.4 - 2.9 Membrane Structure and Function
Membrane function: selective permeability (controlling entry and exit).
Phospholipids form the framework (fluid mosaic model).
Proteins and cholesterol are also present, all moving around.
Cholesterol acts as a fluidity buffer (stabilizes at high temps, remains fluid at low temps).
Membrane molecules and their functions:
Phospholipids: framework.
Cholesterol: fluidity buffer.
Proteins: transport, cytoskeleton attachment, membrane-embedded enzymes, signal transduction, cell-cell recognition.
Membrane transport:
Diffusion: movement from high to low concentration (spontaneous, no energy required), down concentration gradients.
Passive transport: allowing diffusion.
Simple diffusion: small, nonpolar molecules (oxygen, carbon dioxide, lipids, steroids, fats).
Facilitated diffusion: polar molecules and ions through protein channels.
Active transport: pumping molecules against the concentration gradient (low to high).
Requires energy (ATP → ADP).
Bulk transport:
Endocytosis: membrane buckles in, brings fluid/materials into a vesicle.
Exocytosis: vesicles fuse with the membrane, dumping contents outside.
Osmosis: diffusion of water from high to low concentration, from hypotonic to hypertonic.
Plant cells favor hypotonic environments.
Water Potential
Formal way to talk about osmosis, movement of water.
Equation:
Adding solute to water decreases its water potential.
Water flows from higher to lower water potential.
Pressure increases water potential, water flows away from high pressure.
2.1-2.11 Cellular Compartmentalization
Cells have internal compartments with special pH and chemistry that allow different parts to do different things.
Endomembrane system: nuclear membrane, rough ER, smooth ER, vesicles, Golgi, lysosomes.
Mitochondria and chloroplasts (not part of endomembrane system): endosymbionts (descendants of formerly independent organisms).
Evolved from free-living bacteria:
Have their own circular DNA.
Replicate through binary fission.
Have bacteria-like ribosomes and perform protein synthesis.
Have two membranes.
Unit 3: Cellular Energetics
Enzymes
Protein catalysts; lower activation energy of reactions.
Highly specific, bind with substrates at active site.
Sensitive to changes in pH or temperature (can be denatured).
Denaturing: change in shape of active site, enzyme can no longer interact with substrate.
Inhibition:
Competitive inhibition: a molecule competes with the substrate for the active site.
Non-competitive inhibition: Molecule binds to an allosteric site (not the active site), changes shape of the active site.
Allosteric regulation: used to modulate enzyme activity.
3.4 Cell Energy
Metabolic pathways: linked series of enzyme-controlled reactions.
Product of one reaction becomes reactant for the next.
Can be linear (glycolysis) or cyclical (Krebs cycle, Calvin cycle).
Reactions: exergonic (release energy) or endergonic (require energy).
Coupled through ATP:
ATP: five-carbon sugar (ribose), a nitrogenous base, and three phosphate groups.
Energy from cellular respiration powers ATP creation from ADP and phosphate (endergonic).
ATP broken down to ADP and phosphate releases energy for cellular work (exergonic powers endergonic).
3.5 Photosynthesis
Photoautotrophs use light energy to combine carbon dioxide and water to create carbohydrates; oxygen is released.
Formula:
Basis of almost every food chain on this planet.
Two phases:
Light reactions: light energy converted into chemical energy (ATP and NADPH).
Calvin cycle: energy in ATP and NADPH converted into carbohydrate (G3P - glyceraldehyde-3-phosphate).
Light reactions:
Light powers electrical current which powers proton pumps that pump protons into the thylakoid space.
Facilitated diffusion through ATP synthase generates ATP.
Photosystems (proteins packed with chlorophylls) take light energy and make it into a flow that flows down an electron transport chain.
Protons accumulate in thylakoid space and diffuse out through ATP synthase channel.
Water molecule is broken apart, releasing oxygen and creating additional protons.
Electron flow to NADP+ which gets reduced to NADPH.
Calvin cycle:
Three phases enable carbon dioxide to be converted into G3P.
Carbon fixation: carbon dioxide incorporated into a six-carbon compound, broken into a three-carbon compound.
Energy investment: ATP and NADPH energize the compound, creating G3P.
Regeneration: G3P is combined and changed in complex ways so that we wind up with RuBP.
3.6 Cellular Respiration
Cells take glucose and convert it into ATP.
Plants do both cellular respiration and photosynthesis.
Four stages/phases: glycolysis, link reaction, Krebs cycle, electron transport chain.
Oxidizing food and creating mobile electron carriers (NADH and FADH2) .
Glycolysis and Krebs cycle also make a little bit of ATP.
Most ATP is created through oxidative phosphorylation and the electron transport chain.
Electron carriers power an electrical current through an electron transport chain in the inner mitochondrial membrane.
Electron energy is used to pump protons from the matrix to the intermembrane space.
Protons diffuse out through ATP synthase channel, their kinetic energy combines ADP and phosphate into ATP.
Oxygen is the final electron acceptor in the electron transport chain.
Anaerobic respiration happens without oxygen and creates much less ATP.
Generates only two ATPs from glycolysis, combined with fermentation.
Fermentation regenerates NAD+ through the reduction of pyruvate.
Unit 4: Cell Communication, Feedback, and the Cell Cycle
Cell Communication
Cells communicate directly by touching or through signals.
Signals (ligands) are complementary to specific receptors.
Three phases when through signals:
Reception of the ligand.
Signal transduction: Signal converted and amplified.
Cellular response:
Gene activation.
Enzyme activation.
G Protein Coupled Receptors
Important example of cell communication.
Receptors
Steroid hormones diffuse through the phospholipid bilayer & bind with cytoplasmic receptors, that then diffuse into the nucleus and activate genes.
4.5 Homeostasis and Feedback
Homeostasis: Maintaining internal conditions at a relatively constant optimal level.
Feedback: Output of a system is also an input to the system.
Negative feedback: output quiets the system.
Positive feedback: accelerates changes and drives the process forward.
Examples:
Glucose homeostasis (insulin and glucagon).
Oxytocin and childbirth.
Ethylene and fruit ripening.
4.6-4.7 The Cell Cycle
Phases of mitosis: I (Interphase) P (Prophase) M (Metaphase) A (Anaphase) T(Telophase) C (Cytokinesis).
Most of the cell cycle is interphase: growth 1 (general growth), synthesis of DNA, and growth 2 (preparation for M phase).
G0 phase: cells become highly specialized, leaving the cell cycle.
Checkpoints: regulate the process, enable cell to pause if conditions aren't met.
Regulation:
External signals from outside the cell.
Internal regulation: Cyclin and cyclin dependent kinases (internal).
Cancer: unregulated cell division caused by mutations.
Proto-oncogenes: increase the rate of cell division.
Tumor suppressor genes: remove cell division inhibitors and undermine checkpoints.
Unit 5: Heredity
Meiosis
Diploid germ cells create haploid sperm and egg cells.
Meiosis one:
Homologous pairs are separated.
Meiosis two:
Sister chromatids are pulled apart.
Four haploid gametes result.
Prophase one: Homologous pairs exchanging pieces of DNA (crossing over). Independent assortment also increases variation.
Meiosis and sexual reproduction generate diversity in 3 ways:
Independent assortment: how maternal and paternal homologous chromosomes can be sent to the next generation independently of one another
Crossing over and genetic recombination.
Fertilization: combines genomes of two individuals.
Sex Determination
Mammals: XXXY sex determination system.
Birds: ZWZZ sex determination system.
Other animals:
Reptiles: Temperature at which an embryo develops determines whether that embryo will be male or female.
Bees and wasps: Males are haploid, females are diploid.
Nondisjunction
Homologous pairs or sister chromatids do not separate correctly.
Can result in:
Trisomy: three chromosomes instead of a homologous pair, like Down syndrome caused by trisomy 21.
Monosomy: one chromosome instead of a homologous pair, like Turner Syndrome.
5.3-5.5 Genetics
Gene: basic unit of heredity passed from parent to offspring.
Molecular genetics: Sequence of nucleotides that codes for RNA or protein.
Key concepts: Mendel’s principle of segregation of alleles, homozygous vs. heterozygous, dominant vs. recessive, genotype vs. phenotype.
Monohybrid cross: cross between two heterozygotes, with a 3:1 phenotypic ratio and 1:2:1 genotypic ratio.
Sex-linked genes are on the X chromosome are not passed on by the father.
Independent assortment is the rule for two gene pairs.
Dihybrid crosses result in a 9:3:3:1 phenotypic ratio in the offspring.
If more than two genes, use the rule of multiplication.
Linked genes are on the same chromosome and are mostly inherited together.
You can look at the amount of recombination that happens in various crossing experiments and you can use those recombination frequencies to generate chromosome maps.
Additional topics:
Nuclear inheritance: genes that are on mitochondria, not on one of the chromosomes in the nucleus.
Incomplete dominance: blending effect between the two alleles.
Genotype interaction: where it's the environment that determines the phenotype rather than just the genes.
Chi-square: analyze the results of genetic crosses.
Unit 6: Gene Expression
6.2 DNA Replication
Semiconservative: original strand separates, each serving as a template for new strand synthesis.
Daughter strands are half new and half old.
Enzymes involved: helicase, DNA polymerase, primase, ligase, and others.
DNA polymerase can only synthesize in the 5' to 3' direction.
Continuous on leading strand, fragmentary on lagging strand (Okazaki fragments, later sealed together).
6.3 Transcription
Making of RNA from a DNA template.