Understanding Cells in Biology

Introduction to Cells

• Cells are the smallest unit of biological study.
• Two main cell categories: Prokaryotic and Eukaryotic.
• Scale Importance: Often images lack scale bars, misleading size perception.

Prokaryotic Cells

• Significantly smaller than eukaryotic cells (0.1 to 5.0 micrometers).
• Simpler structure, less internal components.
  • DNA: Single, circular chromosome, possibly with plasmids.
• Protective cell wall and plasma membrane, sometimes additional capsule.
• Projections like flagella or pili for movement.
• Reproduction: Binary fission (cell splits into two, creating a clone).

Eukaryotic Cells

• Larger (10 to 100 micrometers) with complex structure.
• Compartmentalized organelles separated by membranes.
  • Organelles Include:
    • Nucleus: Membrane-enclosed, holds linear DNA chromosomes.
    • Mitochondria: Produces ATP, double membrane with cristae and matrix.
    • Ribosomes: Build proteins, not membrane-bound.
    • Endoplasmic Reticulum (ER):
      • Rough ER (RER): With ribosomes, protein synthesis.
      • Smooth ER (SER): Lipid creation, calcium storage.
    • Golgi Apparatus: Modifies, sorts, and secretes cellular components.
    • Lysosome: Contains digestive enzymes.
    • Cell Membrane: Controls substance movement.
  • Plant Cells Specifics:
    • Chloroplast: Photosynthesis, converts sunlight to sugar.
    • Central Water Vacuole: Provides structural support through pressure.
    • Cell Wall: Made of cellulose for additional support.
  • Common to Both Plant and Animal:
    • Centrioles: Assist in cell division.
    • Peroxisomes: Break down specific substances.

Tools for Studying Cells

• Microscopes: Key tools for studying cells.
  • Light Microscope: Uses light, magnifies into thousands times.
  • Electron Microscopes:
    • Transmission Electron Microscope (TEM): Electrons pass through specimen.
    • Scanning Electron Microscope (SEM): Electrons bounce off, 3D images.
  • Electron microscopes have greater magnification and resolution; however, color is lost.

Summary

• Understanding cell types and their characteristics is crucial for biology.
• Microscopy is essential for studying cell structures.
• Important distinctions exist between prokaryotic and eukaryotic cells in terms of size, complexity, and organelles.