Table of Contents

Study Tips

Active Recall

Test yourself without notes to strengthen memory

Spaced Repetition

Review material over increasing time intervals

Dual Coding

Combine verbal and visual information for better retention

1. Water and Its Properties

Key Properties of Water

Water's unique properties stem from its polar covalent bonds and hydrogen bonding.

Essential Properties:

  • Cohesion: Water molecules stick to each other via hydrogen bonds
  • Adhesion: Water molecules stick to other surfaces
  • High Specific Heat: Resists temperature changes (4.184 J/g°C)
  • High Heat of Vaporization: Requires much energy to change from liquid to gas
  • Universal Solvent: Dissolves polar and ionic substances
  • Expansion Upon Freezing: Ice is less dense than liquid water

Biological Significance:

  • Capillary Action: Enables water movement in plants (xylem vessels)
  • Temperature Regulation: Moderates climate and organism temperatures
  • Evaporative Cooling: Sweating in mammals, transpiration in plants
  • Habitat Preservation: Ice floats, insulating aquatic life below

Hydrogen Bonding

Hydrogen bonds form between the slightly positive hydrogen atoms and slightly negative oxygen atoms of adjacent water molecules.

Strength: Individually weak (~5% of covalent bond strength) but collectively strong.

2. Chemical Bonds and Molecular Interactions

Types of Chemical Bonds

Bond Strength Comparison:

Covalent > Ionic > Hydrogen > Van der Waals

Bond Type Description Example in Biology
Covalent Sharing of electron pairs between atoms DNA backbone, peptide bonds in proteins
Ionic Transfer of electrons creating ions NaCl in body fluids, nerve impulse transmission
Hydrogen Between H and electronegative atoms (O, N, F) DNA base pairing, protein folding, water properties
Van der Waals Weak, temporary attractions between molecules Enzyme-substrate binding, gecko foot adhesion

3. Biomolecules

The Four Major Biomolecules

Condensation vs. Hydrolysis:

  • Condensation (Dehydration Synthesis): Monomers → Polymer + H₂O
  • Hydrolysis: Polymer + H₂O → Monomers

Carbohydrates

General Formula: (CH₂O)ₙ | Functions: Energy, structure, recognition

  • Monosaccharides: Glucose, fructose, galactose
  • Disaccharides: Maltose (glucose+glucose), Sucrose (glucose+fructose), Lactose (glucose+galactose)
  • Polysaccharides: Starch (plants), Glycogen (animals), Cellulose (plant cell walls), Chitin (fungi/arthropods)

Lipids

Characteristics: Hydrophobic, diverse structures

  • Fats/Triglycerides: Energy storage, insulation
  • Phospholipids: Membrane structure (amphipathic)
  • Steroids: Cholesterol (membrane fluidity), hormones
  • Waxes: Protection, waterproofing

Proteins

Building Blocks: 20 amino acids with variable R groups

Protein Structure Levels:

  1. Primary: Amino acid sequence (peptide bonds)
  2. Secondary: α-helix and β-pleated sheets (hydrogen bonds)
  3. Tertiary: 3D folding (hydrophobic interactions, disulfide bridges, etc.)
  4. Quaternary: Multiple polypeptide chains (e.g., hemoglobin)

Nucleic Acids

  • DNA: Double helix, stores genetic information
  • RNA: Single-stranded, involved in protein synthesis
  • Nucleotides: Sugar + phosphate + nitrogenous base

4. Cell Structure and Function

Eukaryotic Cell Organelles

Endomembrane System:

Nuclear envelope → ER → Golgi → vesicles → plasma membrane

Key Organelles and Functions:

  • Nucleus: Contains DNA, controls cell activities
  • Ribosomes: Protein synthesis (free or RER-bound)
  • Endoplasmic Reticulum: Rough (protein synthesis), Smooth (lipid synthesis, detox)
  • Golgi Apparatus: Modifies, sorts, packages proteins/lipids
  • Lysosomes: Intracellular digestion, recycling
  • Mitochondria: Cellular respiration, ATP production
  • Chloroplasts: Photosynthesis (plants only)
  • Vacuoles: Storage, waste disposal, water balance
  • Cytoskeleton: Structural support, cell movement, transport

Animal vs. Plant Cells:

  • Animal Cells: Centrioles, lysosomes, extracellular matrix
  • Plant Cells: Cell wall (cellulose), chloroplasts, large central vacuole

5. Membrane Structure and Transport

Fluid Mosaic Model

Phospholipid bilayer with embedded proteins that can move laterally within the layer.

Membrane Protein Functions:

  1. Transport
  2. Enzymatic activity
  3. Signal transduction
  4. Cell-cell recognition
  5. Intercellular joining
  6. Attachment to cytoskeleton and ECM

Transport Mechanisms

Passive Transport (No energy required):

  • Simple Diffusion: Movement from high to low concentration
  • Facilitated Diffusion: Through transport proteins
  • Osmosis: Water diffusion across membrane

Tonicity:

  • Hypertonic: Higher solute concentration → cell shrinks
  • Hypotonic: Lower solute concentration → cell swells
  • Isotonic: Equal concentration → no net movement

Active Transport (Requires ATP):

  • Primary Active Transport: Direct ATP use (Na⁺/K⁺ pump)
  • Secondary Active Transport: Uses ion gradients (cotransport)
  • Bulk Transport: Endocytosis (phagocytosis, pinocytosis, receptor-mediated) and Exocytosis

6. Enzymes and Metabolism

Enzyme Characteristics

  • Biological catalysts (usually proteins)
  • Lower activation energy
  • Specific to substrates
  • Not consumed in reactions
  • Work via induced fit model

Factors Affecting Enzyme Activity

  1. Temperature: Increases activity to optimum, then denatures
  2. pH: Each enzyme has optimal pH
  3. Substrate Concentration: Increases activity until saturation
  4. Inhibitors: Competitive, noncompetitive, allosteric
  5. Cofactors/Coenzymes: Assist enzyme function

Enzyme Regulation:

  • Feedback Inhibition: End product inhibits early enzyme
  • Cooperativity: Substrate binding enhances further binding

7. Study Strategies and Resources

Effective Study Methods

  1. Active Recall: Test yourself without notes
  2. Spaced Repetition: Review material over increasing intervals
  3. Interleaving: Mix different topics in study sessions
  4. Elaboration: Explain concepts in your own words
  5. Dual Coding: Combine verbal and visual information

Recommended Resources

  • Textbook: Campbell Biology (AP Edition)
  • Online Resources: Bozeman Science, Khan Academy AP Biology, College Board AP Classroom
  • Practice Materials: Past AP Biology exams, Princeton Review, Barron's

8. Common Misconceptions to Avoid

Misconceptions and Corrections

  • Misconception: "Water molecules are bonded together"
    Correction: They're connected by hydrogen bonds, not covalent bonds
  • Misconception: "Enzymes are used up in reactions"
    Correction: They're catalysts and are recycled
  • Misconception: "Active transport always moves against concentration gradient"
    Correction: Cotransport can use gradients to move other substances
  • Misconception: "All cells have a cell wall"
    Correction: Only plants, fungi, bacteria, and some protists do
  • Misconception: "Osmosis is the diffusion of water from low to high concentration"
    Correction: Actually from high water concentration (low solute) to low water concentration (high solute)

9. Final Preparation Checklist

Pre-Exam Checklist

Exam Day Preparation:

  • Get adequate sleep the night before
  • Eat a balanced meal before the exam
  • Bring required materials (calculator, pencils, ID)
  • Manage time carefully during the exam
  • Review answers if time permits

Practice Quiz

Test your knowledge with these sample questions

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