Lecture Notes: Chapter 1 - Cell Structure

Overview

• Chapter Parts:
  1. Microscopy
  2. Calculation (Magnification)
  3. Cell Structure and Function

Microscopy

• Main Microscopes:
  1. Light Microscope
  2. Electron Microscope
     • Transmission Electron Microscope
     • Scanning Electron Microscope

Key Concepts

• Electromagnetic Radiation

  • Light Microscopes: Use visible light.
  • Electron Microscopes: Use electrons.

• Magnification vs Resolution

  • Magnification: Enlarging an image relative to the object's actual size.
    • Notation: Times sign (x), e.g., x10, x40.
  • Resolution: Ability to distinguish two points as separate.
    • Units: Nanometers (nm).
    • Higher resolution means clearer distinction.

Differences Between Magnification and Resolution

• Increasing magnification does not increase resolution.
• Resolution determined by the wavelength of electromagnetic radiation.
  • Shorter wavelength = higher resolution.

Light Microscope

• Source: Visible light (400-700 nm wavelength).
• Max Magnification: x1,500.
• Max Resolution: 200 nm.
• Advantages:
  • View live specimens.
  • Possible to see color (stained or natural).
  • Inexpensive and accessible.
• Disadvantages:
  • Lower resolution compared to electron microscopes.

Electron Microscope

• Source: Free electrons (~1 nm wavelength).
• Max Magnification: x250,000.
• Max Resolution: 0.5 nm.
• Advantages:
  • Very high magnification and resolution.
  • Can view structures at the nanometer level.
• Disadvantages:
  • Can only view dead specimens (vacuum environment required).
  • Images are initially black and white.
  • Expensive and large equipment.

Types of Electron Microscopes

• Transmission Electron Microscope (TEM):

  • Views internal structure by passing electrons through specimen.
  • 2D images.
  • Specimens must be thinly sliced.

• Scanning Electron Microscope (SEM):

  • Views surface structure of specimens.
  • 3D images.
  • Lower resolution than TEM but provides detailed surface images.

Exam Tips

• Comparing Microscopes:
  • Use tables in exams to compare features of light and electron microscopes.
  • Include magnification, source of radiation, resolution, etc.
  • Use comparative language clearly (e.g., bigger/smaller, present/absent).
• Common Questions: Differences between types of microscopes, magnification vs resolution.