4.1 Studying Cells - Biology 2e | OpenStax

Introduction to Cells

• Cells are the smallest unit of a living organism.
• Organisms can be unicellular (one cell, e.g., bacteria) or multicellular (many cells, e.g., humans).
• Cells form tissues, tissues form organs, organs form organ systems, and organ systems form organisms.
• Two main types of cells: Prokaryotic (e.g., bacteria) and Eukaryotic (e.g., plant and animal cells).

Microscopy

• Microscopes are necessary to view cells, which are typically too small to see with the naked eye.
• Light Microscopes:
  • Use visible light to view specimens.
  • Useful for viewing living organisms.
  • Magnification typically up to 400x.
  • Require staining to enhance visibility, which can kill cells.
  • Two main parameters: magnification (enlarging an image) and resolving power (clarity/detail).
• Electron Microscopes:
  • Use a beam of electrons for higher magnification and resolution.
  • Magnification up to 100,000x with a resolution of 50 picometers.
  • Requires a vacuum, which kills the specimen.
  • Two types:
    • Scanning Electron Microscope (SEM): Studies surface details.
    • Transmission Electron Microscope (TEM): Studies internal structures.

Cell Theory

• Developed based on observations by van Leeuwenhoek and others in the 1600s.
• Key contributors: Robert Hooke, Matthias Schleiden, Theodor Schwann, and Rudolf Virchow.
• Unified cell theory:
  • All living things are composed of one or more cells.
  • The cell is the basic unit of life.
  • New cells arise from existing cells.

Career Connection: Cytotechnologist

• Cytotechnologists study cells to identify diseases, abnormalities, or infections.
• They play a critical role in medical testing like Pap smears to detect cervical cancer.

Visual Aids

• Diagrams and micrographs illustrate cell structures and the differences between light and electron microscopy.

Learning Objectives

• Understand the role of cells in organisms.
• Compare light microscopy with electron microscopy.
• Summarize cell theory.