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Overview of Multicellular Organism Biology

May 7, 2025

Lecture Notes: Multicellular Organisms and Basic Biological Concepts

A. Levels of Organization

  • Atoms: Basic units of matter (e.g., carbon, hydrogen, oxygen)
  • Molecules: Atoms bonded (e.g., water, proteins, DNA)
  • Organelles: Structures in cells made of molecules (e.g., mitochondria)
  • Cells: Basic units of life; different types for different functions (e.g., muscle cells)
  • Tissues: Groups of similar cells performing a function (e.g., muscle tissue)
  • Organs: Composed of tissues working together (e.g., heart)
  • Organ Systems: Groups of organs (e.g., digestive system)
  • Organism: Complete living being

Homeostasis and Feedback Mechanisms

  • Homeostasis: Maintaining a stable internal environment
  • Negative Feedback: Restores balance (e.g., sweating to cool down)
  • Positive Feedback: Increases change temporarily (e.g., childbirth)

B. Metric System

  • Basic units:
    • Length: Meter (m)
    • Mass: Gram (g)
    • Time: Second (s)
    • Volume: Liter (L)
  • Prefixes:
    • Kilo = 1,000
    • Deci = 1/10
    • Centi = 1/100
    • Milli = 1/1,000
    • Micro = 1/1,000,000
    • Nano = 1/1,000,000,000
  • Conversion Steps: Identify units, count steps, move decimal

C. Atoms, Molecules, Bonds, and Matter

  1. Element: Pure substance of one type of atom
  2. Common Symbols: O, C, H, N, Ca, K, Na, Cl, Fe, P
  3. Chemical Formulas:
  • CO₂, H₂O, NaCl
  1. Atom Structure:
  • Protons: Positive, nucleus
    • Neutrons: Neutral, nucleus
    • Electrons: Negative, orbits
  1. Isotope: Same protons, different neutrons
  2. Isotopes in Medicine: E.g., I-131 for thyroid
  3. Molecule vs. Ion:
  • Molecule: Atoms bonded
    • Ion: Charged atom/molecule
  1. Covalent vs. Ionic Bonds:
  • Covalent: Shared electrons
    • Ionic: Transferred electrons
  1. Bond Strength:
  • Covalent > Ionic
  1. Polar vs. Nonpolar:
  • Polar: Unequal sharing (e.g., water)
    • Nonpolar: Equal sharing
  1. Hydrogen Bond: Weak attraction, important in water & DNA
  2. Matter: Anything with mass and space
  3. States of Matter: Solid, liquid, gas
  4. Particle Motion: Increases with temperature
  5. Temperature, Pressure, Volume: Relationship described by gas laws

D. Water

  1. Polarity of Water: Polar molecule with partial charges
  2. Hydrogen Bonds: Between water contributes to high boiling point
  3. Biological Importance: Cohesion, protein structure, DNA stability

E. Acids, Bases, pH, and Buffers

  1. Acid: Donates H⁺ ions
  2. Base: Accepts H⁺ or releases OH⁻
  3. pH Scale:
  • 0-6: Acidic
    • 7: Neutral
    • 8-14: Basic
  1. Buffer: Resists pH changes
  2. Dissociation: Molecule forms ions in water
  3. Neutralization Reaction: Acid + Base → Water + Salt

F. Chemical Reactions

  1. Kinetic vs. Potential Energy
  2. Energy in Reactions: Release or require energy
  3. Chemical Equilibrium: Forward and reverse reaction rates equal
  4. Enzymes: Catalysts, specificity, work by lowering activation energy
  5. Factors Affecting Enzyme Activity: pH, temperature

G. Biomolecules

  1. Carbon: Versatile bonding properties
  2. Monomer vs. Polymer
  3. Carbohydrates: Monosaccharides, Disaccharides, Polysaccharides
  4. Proteins:
  • Amino Acids: Building blocks, peptide bonds
    • Protein Structure: Primary to Quaternary
  1. Nucleic Acids: DNA and RNA, nucleotide structure
  2. ATP: Energy currency
  3. Lipids: Hydrophobic molecules, types include triglycerides

H. DNA, RNA, and Protein Synthesis

  1. DNA Replication: Making an exact copy
  2. Transcription & Translation: Transcribe DNA to mRNA, translate mRNA to protein
  3. mRNA, tRNA, rRNA: Roles in protein synthesis

I. Structure and Function of Cells

  1. Cell Theory: All living things are cells
  2. Cell Structures: Plasma membrane, nucleus, cytoplasm
  3. Organelles: Ribosomes, ER, Golgi apparatus

J. Plasma Membrane

  1. Structure: Phospholipid bilayer, proteins, cholesterol
  2. Functions: Transport, signaling

K. Energy and Cells

  1. ATP & ADP: Energy transfer
  2. Cellular Respiration: Glycolysis, Citric Acid Cycle, Oxidative Phosphorylation

L. Mitosis and Meiosis

  1. Mitosis: Cell division for growth
  2. Meiosis: Gamete production, genetic variation

M. Body Systems

  1. Circulatory System: Transports blood and nutrients
  2. Digestive System: Breaks down food
  3. Nervous System: Controls body activities
  4. Endocrine System: Regulates via hormones
  5. Reproductive System: Produces offspring
  6. Integumentary System: Protects body, regulates temperature
  7. Skeletal System: Supports body, stores minerals
  8. Respiratory System: Gas exchange
  9. Muscular System: Allows movement
  10. Urinary System: Removes waste
  11. Immune System: Protects against pathogens