Biology Notes: Modules 1-3 (Brief)

Module 1: Introduction to Biology

• Properties of life: Order; response to stimuli; reproduction; adaptation; growth & development; regulation; homeostasis; energy processing
• Levels of organization (small → large): $\text{Molecule} \rightarrow \text{Cell} \rightarrow \text{Tissue} \rightarrow \text{Organ} \rightarrow \text{Organ system} \rightarrow \text{Organism} \rightarrow \text{Population} \rightarrow \text{Community} \rightarrow \text{Ecosystem} \rightarrow \text{Biosphere}$
• Three domains of life: Bacteria, Archaea, Eukarya
• Taxonomy (largest → smallest): Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
• Binomial nomenclature: Scientific name = Genus + species
• Phylogenetic tree: Diagram showing evolutionary relationships
• Observation (scientific method) → Information gathered with senses; Hypothesis → Proposed explanation; Prediction → Testable statement from hypothesis; Experiment → Controlled test; Conclusion → Support or reject hypothesis
• Variables: Independent variable → The factor that is changed; Dependent variable → The factor that is measured; Control variable → Factors kept constant
• Reasoning: Deductive reasoning → General → specific; Inductive reasoning → Specific → general

Module 2: Chemistry of Life

• Matter → Anything that takes up space and has mass
• Element → Substance that cannot be broken down
• Atom → Smallest unit of an element
• Subatomic particles → Protons (+, nucleus); Neutrons (0, nucleus); Electrons (−, orbitals)
• Atomic number → #\text{protons}; Mass number → Protons + neutrons
• Isotopes → Same element, different neutrons
• Valence shell → Outermost electron shell; Valence electrons → Electrons in outer shell
• Ionic bond → Transfer of electrons (cation +, anion -)
• Covalent bond → Sharing electrons
• Nonpolar covalent → Equal sharing; Polar covalent → Unequal sharing
• Hydrogen bonds → Weak attraction between slightly + hydrogen and slightly − atom
• Bond strength (strongest → weakest) → Covalent > Ionic > Hydrogen
• Water is polar → Regions of partial + and − charges
• Properties of water → Stabilizes temperature, excellent solvent, cohesive/adhesive
• Cohesion → Water molecules stick to each other; Adhesion → Water molecules stick to other surfaces
• pH scale → $0-14$
• Acid → $pH < 7$; Base → $pH > 7$; Neutral → $pH = 7$
• Buffers → Maintain stable pH in organisms (e.g., CO₂ in blood)

Module 3: Biological Macromolecules

• Organic molecules → Always contain carbon
• Why carbon forms 4 bonds? → 4 valence electrons
• Monomer → Small building block; Polymer → Chain of monomers
• Dehydration reaction → Joins monomers into polymers (removes water)
• Hydrolysis → Breaks polymers into monomers (adds water)
• Carbohydrates
  • General formula → $C(H<em>2O)</em>n$
  • Function → Energy, cell wall structure
  • Monosaccharide → 1 sugar (ex: glucose)
  • Disaccharide → 2 sugars via dehydration (ex: sucrose, maltose, lactose)
  • Polysaccharide → Long sugar chains
  • Starch → Energy storage in plants
  • Cellulose → Cell walls in plants
  • Glycogen → Energy storage in humans
  • Sugar suffix → -ose
• Lipids → Nonpolar, hydrophobic
  • Functions → Long-term energy, insulation, hormones, membranes, waterproofing
  • Fat (triglyceride) → Glycerol + 3 fatty acids
  • Fatty acids → Saturated → Single bonds, straight, solid at room temp; Unsaturated → Double bonds, bent, liquid at room temp
  • Phospholipids → Cell membranes; Head = hydrophilic; Tail = hydrophobic
  • Steroids → Fused ring structures (cholesterol, hormones)
  • Waxes → Prevent water sticking to surfaces
• Proteins → Monomer = Amino acid
  • Amino acid components → Amino group, carboxyl group, R group, hydrogen
  • Primary structure → Amino acid sequence
  • Secondary structure → α-helix or β-sheet (H bonds)
  • Tertiary structure → 3D folding (R group interactions)
  • Quaternary structure → Multiple polypeptides
  • Denaturation → Protein loses shape (heat, pH, salt)
  • Functions → Enzymes, structure, hormones, defense, transport
  • Enzymes → Speed up chemical reactions
  • Protein function depends on → Shape
• Nucleic Acids
  • Monomer → Nucleotide = sugar + phosphate + base
  • DNA → Sugar = deoxyribose; Bases = A, T, C, G
  • RNA → Sugar = ribose; Bases = A, U, C, G
  • DNA function → Stores genetic information
  • RNA functions → mRNA, rRNA, tRNA
  • Base pairs (DNA) → A–T, C–G
  • Base pairs (RNA) → A–U, C–G