Overview
This lecture provides a comprehensive review of key high school biology concepts, covering the properties of water, macromolecules, cell structure and function, genetics, evolution, ecology, and human impacts on ecosystems.
Properties of Water
- Water is a polar molecule, making it a universal solvent for many substances.
- Cohesion is water's attraction to itself; adhesion is its attraction to other substances.
- Surface tension results from water molecules being more attracted to each other than to air.
- Water has high specific heat and heat of vaporization, helping regulate temperature in organisms.
- Hydrophilic molecules dissolve in water; hydrophobic molecules do not.
Macromolecules and Their Functions
- Carbohydrates: Energy storage and structure; monomer is monosaccharide (glucose).
- Lipids: Long-term energy, insulation, and cell membranes; monomer is fatty acid.
- Proteins: Structure, enzyme catalysis, signaling; monomer is amino acid.
- Nucleic acids: Genetic information storage (DNA, RNA); monomer is nucleotide.
- Lab tests: Biuret for proteins, Benedict’s for simple sugars, iodine for starch, paper bag for lipids.
Cell Structure and Function
- Prokaryotes lack nuclei and membrane-bound organelles; eukaryotes have both.
- Plant cells have cell walls, chloroplasts, and large vacuoles; animal cells do not.
- Key organelles: nucleus (DNA storage), mitochondria (energy), ribosomes (protein synthesis), chloroplasts (photosynthesis), vacuole (storage), ER (transport), Golgi (packaging).
- The cell membrane is a phospholipid bilayer with proteins and cholesterol; controls transport and communication.
Cell Transport
- Passive transport: Simple diffusion, facilitated diffusion (uses proteins, no energy).
- Active transport: Moves substances against gradient, requires energy (ATP).
- Osmosis: Diffusion of water towards higher solute concentration.
- Tonicity: Isotonic (equal), hypotonic (low solute outside, water in), hypertonic (high solute outside, water out).
Enzymes
- Enzymes are proteins that speed up reactions by lowering activation energy.
- They are specific, reusable, and affected by temperature, pH, substrate, and inhibitors.
- Denaturation occurs when enzymes lose their shape due to extreme conditions.
Photosynthesis and Cellular Respiration
- Photosynthesis: Sunlight + CO₂ + H₂O → glucose + O₂ (in chloroplasts).
- Cellular respiration: Glucose + O₂ → CO₂ + H₂O + ATP (in mitochondria).
- Aerobic respiration produces 36 ATP; fermentation (anaerobic) produces 2 ATP.
- Plants and animals both perform respiration, but only plants (and some bacteria) photosynthesize.
Genetics and Heredity
- DNA is organized into chromosomes, chromatin, and chromatids.
- Mitosis: One cell divides into two identical diploid cells (growth, repair).
- Meiosis: One cell divides into four haploid gametes (reproduction, genetic variation).
- Genetic variation arises from crossing-over, independent assortment, and random fertilization.
- Genotype: allele combination; phenotype: physical trait; homozygous: same alleles; heterozygous: different alleles.
Patterns of Inheritance
- Mendel's Laws: Segregation, independent assortment, dominance.
- Incomplete dominance: Blended traits; codominance: both traits shown.
- Multiple alleles and sex-linked traits (e.g., colorblindness on X chromosome).
- Environmental factors can alter gene expression (epigenetics).
Mutations and Chromosomal Disorders
- Mutations can cause genetic disorders; only passed to offspring if in gametes.
- Non-disjunction leads to chromosomal disorders (e.g., Down syndrome).
- Karyotyping and amniocentesis used for detecting chromosomal abnormalities.
DNA, RNA, and Protein Synthesis
- DNA: Double-stranded, deoxyribose sugar, bases A-T, G-C.
- RNA: Single-stranded, ribose sugar, bases A-U, G-C.
- DNA replication is semi-conservative, assisted by ligase, helicase, polymerase.
- Protein synthesis: Transcription (DNA → mRNA), translation (mRNA → protein at ribosome).
Biotechnology
- PCR amplifies DNA; gel electrophoresis separates DNA fragments by size.
- Genetic engineering uses plasmids and restriction enzymes to insert genes.
- Applications include medicine, agriculture, and forensics; raises ethical questions.
Evolution and Natural Selection
- Evolution: Change in genetic makeup of populations over time, not individuals.
- Natural selection: Organisms with favorable traits survive/reproduce more.
- Evidence: Fossils, embryology, molecular data, morphology.
- Hardy-Weinberg Equilibrium models allele frequencies in non-evolving populations.
Classification and Phylogeny
- Three domains: Bacteria, Archaea, Eukarya; Eukarya includes plants, animals, fungi, protists.
- Binomial nomenclature uses genus and species for naming.
- Cladograms and phylogenetic trees show evolutionary relationships.
Ecology and Ecosystems
- Energy flows from producers to consumers; only 10% transferred at each trophic level.
- Matter cycles: Carbon, nitrogen, water cycles involve all ecosystem components.
- Biodiversity increases ecosystem resilience; keystone species have large effects.
- Population dynamics influenced by limiting factors and carrying capacity.
- Symbiosis types: mutualism (+/+), parasitism (+/-), commensalism (+/0).
Human Impact on the Environment
- Human activities cause habitat loss, pollution, introduction of invasive species, and global climate change.
- Conservation actions: Reduce, reuse, recycle, plant natives, support sustainability.
- Renewable resources replenish quickly; nonrenewable take millions of years to form.
Key Terms & Definitions
- Cohesion — attraction between water molecules.
- Adhesion — attraction of water to other substances.
- Osmosis — movement of water across a membrane from high to low concentration.
- Enzyme — protein catalyst that speeds up chemical reactions.
- Genotype — genetic allele combination of an organism.
- Phenotype — observable physical trait of an organism.
- Homozygous/Heterozygous — same/different alleles for a gene.
- Mutation — change in DNA sequence.
- Hardy-Weinberg Equilibrium — model predicting allele frequencies in a non-evolving population.
- Autotroph/Heterotroph — organisms that make/consume food.
- Keystone Species — species with a disproportionately large impact on ecosystem.
- Carrying Capacity — maximum population size an environment can support.
Action Items / Next Steps
- Review course textbook diagrams for cell structures, mitosis/meiosis, and phylogenetic trees.
- Practice Punnett square and Hardy-Weinberg problems.
- Review lab techniques: gel electrophoresis, PCR.
- Read assigned chapters covering ecology and environmental science.