Cell Structure - Lecture Notes

Chapter Outline

1. Microscopy
   • Magnification vs Resolution
   • Light Microscope vs Electron Microscope
2. Micrometry: How do we measure cells?
   • Calibrating EPG using the Stage Micrometer
   • Magnification
3. Cell Structure and Function
   • Organelles
   • Animal vs Plant cells
   • Eukaryotes vs Prokaryotes
   • Viruses

Microscopy

Types of Microscopes

• Light Microscope
  • Uses visible light
  • Wavelength: 400-700 nm
  • Magnification: x1,500
  • Max resolution: 200 nm
  • Advantages: Live specimens, color images
• Electron Microscope
  • Uses free electrons
  • Wavelength: ~1 nm
  • Magnification: x250,000
  • Max resolution: 0.5 nm
  • Disadvantages: Only dead specimens, black and white images
  • Types:
    • Transmission Electron Microscopes (TEM) - 2D images, internal structures
    • Scanning Electron Microscopes (SEM) - 3D surface images

Magnification and Resolution

• Magnification: Number of times an image is enlarged compared to the actual size
• Resolution: Ability to distinguish two points as separate
  • Higher resolution with shorter wavelength

Micrometry: Measuring Cells

• Units:
  • Light Microscope: micrometre (µm)
  • Electron Microscope: nanometre (nm)
• Calibration: Use stage micrometer and eyepiece graticule (EPG)
  • Example: 1 EPG = 6.67 µm
• Exercise: Calculate actual size using magnification formula

Cell Structure and Function

Cell Organelles

• Nucleus: Largest organelle, contains genetic material
• Ribosomes: Site of protein synthesis
• Endoplasmic Reticulum (ER):
  • Rough ER: Protein synthesis and modification
  • Smooth ER: Lipid synthesis
• Golgi Body: Modifies, packages proteins, and forms lysosomes
• Lysosomes: Digest unwanted structures
• Mitochondria: Site of aerobic respiration, ATP production
• Chloroplasts: Site of photosynthesis in plant cells
• Cell Wall: Provides structural support in plant cells
• Plasmodesmata: Channels for transport between plant cells
• Vacuoles: Storage and maintaining cell turgidity
• Centrioles: Involved in cell division
• Microtubules: Part of the cytoskeleton, transportation
• Cilia and Microvilli: Surface area increase, movement

Cell Comparison

• Animal vs Plant Cells:
  • Animal: No fixed shape, no cell wall, centrosomes present
  • Plant: Fixed shape, cell wall and chloroplasts present
• Prokaryotes vs Eukaryotes:
  • Prokaryotes: No nucleus, smaller, simpler
  • Eukaryotes: Membrane-bound organelles, larger

Viruses

• Non-cellular, parasitic, require host cells to reproduce

Conclusion

• Cell structure and function are vital in understanding biological processes
• Different microscopes and techniques are crucial for exploring cellular components

Note: These notes summarize the key points from the lecture on cell structure, microscopy, and cell function. It's important to review diagrams and perform exercises to solidify understanding.