Chapter 4: Introduction to Cells

Overview

• Focus on cells: prokaryotic and eukaryotic cells
• Cells are the smallest unit of life
  • All living things comprised of cells
• Types of cells:
  • Prokaryotic cells
  • Eukaryotic cells

Types of Cells and Organisms

• Unicellular organisms: Single-celled organisms
• Multicellular organisms: Composed of multiple cells working together
  • Example: Humans with complex systems like cardiovascular and respiratory systems

Microscopy

• Microscopes
  • Tools to visualize cells, which are typically invisible to the naked eye
  • Magnification depends on lens type
  • Resolving Power: Ability to distinguish separate structures
    • Higher resolving power = better detail
• Types of microscopes
  • Light Microscopes
    • Use visible light
    • Common in labs
  • Electron Microscopes
    • Higher magnification and resolution
    • Types:
      • Transmission Electron Microscope (TEM): Detailed view within cells
      • Scanning Electron Microscope (SEM): 3D exterior views
• Staining
  • Used with light microscopes to add color to transparent cells
  • Can kill cells
  • Phase Contrast Microscopes
    • Rare in labs
    • Allow viewing of live specimens without staining

Cell Theory

• Cells are basic units of life
• All living things made of one or more cells
• All cells arise from pre-existing cells

Basic Cell Components

• Cell (Plasma) Membrane: Protects cell interior
• Cytoplasm: Contains cell contents
  • Cytosol: Liquid component
• DNA: Genetic material
• Ribosomes: Protein synthesis

Prokaryotic Cells

• Characteristics:
  • Lack a nucleus
  • No membrane-bound organelles
  • DNA in nucleoid region
• Mostly bacteria
  • Cell walls contain peptidoglycan
• Prokaryotic Structures
  • Cell Membrane and Cell Wall
  • Nucleoid: Region with DNA
  • Ribosomes
  • May have:
    • Flagellum: Movement
    • Pili: Attachment
    • Capsule: Protection, prevent dehydration

Cell Size and Efficiency

• Surface Area to Volume Ratio
  • Smaller cells have higher efficiency for nutrient uptake and waste elimination
  • As cells grow, surface area increases slower than volume
• Adaptations to Increase Efficiency
  • Cell division to increase surface area
  • Membrane invaginations
  • Flatter or thinner shapes in larger cells

Conclusion

• Review of prokaryotic cells
• Upcoming: Detailed study of eukaryotic cells in Part 2