Cellule e Microscopia

Cells and Microscopes

• Cells are the basic units of life. They can be prokaryotic (lacking a nucleus) or eukaryotic (containing a nucleus).
• Microscopes are essential tools for observing cells, enabling us to see structures that are too small to be visible with the naked eye.

Types of Microscopes

• Light Microscope (LM): Uses visible light to magnify images. Can view living cells, but has a limited resolving power (ability to distinguish between two closely spaced objects).
  • Components:
    • Eyepiece: Magnifies the image further.
    • Objective lenses: Multiple lenses with varying magnification levels.
    • Stage: Supports the specimen.
    • Condenser: Focuses light onto the specimen.
    • Light source: Illuminates the specimen.
    • Coarse and fine adjustment knobs: Focus the image.
• Electron Microscope (EM): Uses a beam of electrons to create highly magnified images. Has much higher resolving power than a light microscope, allowing for detailed observation of cellular structures.
  • Types: Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM).
  • TEM: Passes electrons through the specimen, providing detailed internal images.
  • SEM: Scans the surface of the specimen with a beam of electrons, producing detailed images of the surface features.
  • Components:
    • Electron gun: Generates a beam of electrons.
    • Electromagnets: Focus and control the electron beam.
    • Vacuum chamber: Prevents electron scattering by air molecules.
    • Image detectors: Capture and display the image.

Cell Structures (Eukaryotic)

• Nucleus: Contains the cell's genetic material (DNA). Controls cell activities.
• Cytoplasm: Gel-like substance filling the cell. Contains organelles.
• Plasma membrane: Outer boundary of the cell, regulating what enters and leaves.
• Mitochondria: "Powerhouses" of the cell, involved in energy production (cellular respiration).
• Ribosomes: Involved in protein synthesis.
• Endoplasmic reticulum (ER): Network of membranes involved in protein and lipid synthesis.
• Golgi apparatus: Modifies, sorts, and packages proteins for secretion.
• Lysosomes: Contain enzymes for breaking down waste materials.
• Vacuoles: Fluid-filled sacs for storage and transport.
• Chloroplasts: Present in plant cells, involved in photosynthesis.
• Cell wall: Provides support and protection in plant cells.

Key Differences Between Cell Types

• Prokaryotic cells: simpler, lack internal membrane-bound organelles (like nucleus, mitochondria).
• Eukaryotic cells: more complex, have membrane-bound organelles.

Cell Size

• Cells are generally microscopic in size, varying widely depending on the organism and cell type.
• Measuring cell sizes are commonly done in micrometers (µm).