Overview
This lecture comprehensively reviews the AP Biology curriculum, summarizing major units including biomolecules, cell structure/function, genetics, evolution, ecology, and biotechnology, focusing on key concepts, mechanisms, and processes essential for exam success.
Chemistry of Life
- Water is a polar molecule with hydrogen bonding, responsible for cohesion, adhesion, and high surface tension.
- Acids have more hydrogen ions (pH < 7); bases have more hydroxide ions (pH > 7).
- Elements essential for life: carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur (CHNOPS).
- Monomers (building blocks) combine to form polymers through dehydration synthesis; hydrolysis breaks them apart.
- Functional groups (e.g., phosphate, methyl, carboxyl, amino) influence biomolecule properties.
Biomolecules
- Four major macromolecules: carbohydrates, lipids, proteins, nucleic acids.
- Carbohydrates: monosaccharides (glucose), disaccharides (lactose), polysaccharides (starch, cellulose, glycogen).
- Lipids: hydrophobic, include triglycerides (energy storage), phospholipids (membranes), steroids (signaling).
- Proteins: made from 20 amino acids, have primary, secondary, tertiary, quaternary structures, function determined by shape.
- Nucleic acids: DNA (genetic info), RNA (information transfer), ATP (energy), made of nucleotide monomers.
Cell Structure and Function
- Cells are the basic unit of life, surrounded by a membrane, containing DNA, and ribosomes.
- Prokaryotes: no nucleus, circular DNA, plasmids, found in Bacteria and Archaea.
- Eukaryotes: nucleus, linear chromosomes, organelles (mitochondria, ER, Golgi, lysosomes).
- Surface area-to-volume ratio limits cell size; cells maximize surface area for efficient diffusion.
Membrane Structure and Transport
- Membranes are phospholipid bilayers with embedded proteins (fluid mosaic model).
- Passive transport: diffusion, osmosis, facilitated diffusion (no energy).
- Active transport: requires energy to move substances against gradients.
- Bulk transport: endocytosis (in), exocytosis (out).
- Membrane potential is an electrical charge difference maintained by ion pumps.
Cell Energetics
- Enzymes catalyze reactions by lowering activation energy, are specific, and affected by pH, temperature, substrate concentration.
- ATP stores and releases energy by adding/removing phosphate groups (energy coupling).
- Photosynthesis: converts COâ‚‚ and Hâ‚‚O into glucose and Oâ‚‚ using light (light reactions and Calvin cycle).
- Cellular respiration: glycolysis, Krebs cycle, electron transport chain convert glucose into ATP; oxygen required for aerobic, fermentation for anaerobic.
Genetics and Inheritance
- DNA is a double helix made of nucleotides (A=T, G≡C), replicated semiconservatively.
- Genes code for proteins via transcription (DNA → RNA) and translation (RNA → protein).
- Mutations include point mutations (silent, missense, nonsense) and frameshifts.
- Mendelian inheritance: segregation, independent assortment, monohybrid/dihybrid crosses, sex linkage.
- Non-Mendelian: linked genes, incomplete dominance, environmental effects.
Evolution and Population Genetics
- Evolution occurs by natural selection, mutation, genetic drift, gene flow, non-random mating.
- Population genetics uses Hardy-Weinberg equations to model allele frequencies.
- Speciation: allopatric (geographic isolation), sympatric (without barrier).
- Evidence for evolution: homologous structures, fossil record, molecular homologies.
Ecology
- Ecosystems consist of living communities and abiotic factors; energy flows via food chains and webs (10% rule).
- Symbiosis: mutualism, commensalism, parasitism, competition.
- Population growth: exponential, logistic, carrying capacity, limiting factors.
- Biodiversity increases ecosystem resilience; human activities threaten biodiversity.
Biotechnology
- Recombinant DNA created using restriction enzymes, ligase, and plasmids.
- Gel electrophoresis and PCR used for DNA analysis and amplification.
- DNA sequencing reveals gene/protein functions and evolutionary relationships.
Key Terms & Definitions
- Hydrogen bond — weak attraction between polar molecules.
- Monomer — simple molecule that is a building block for polymers.
- Dehydration synthesis — chemical reaction that joins monomers by removing water.
- Phospholipid bilayer — core structure of cell membranes.
- Enzyme — protein catalyst for biochemical reactions.
- ATP — adenosine triphosphate, main energy currency of the cell.
- Gene — DNA sequence coding for a functional product.
- Mutation — random change in DNA sequence.
Action Items / Next Steps
- Review provided checklists for each unit.
- Memorize key formulas (e.g., Hardy-Weinberg, water potential).
- Practice with sample problems and diagrams (e.g., Punnett squares, food webs).
- Complete readings and tutorials as assigned.