뒤로Tour of the Cell: Structure, Function, and Microscopy
스터디 가이드 - 스마트 노트
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Tour of the Cell
Microscopes in Cell Biology
Microscopes are essential tools for studying cells, allowing scientists to observe structures not visible to the naked eye. There are several types of microscopes, each with unique capabilities.
Compound Light Microscopes: Use two lenses (ocular and objective) to magnify specimens up to 400X. Total magnification is calculated by multiplying the magnification of the ocular lens by the objective lens.
Electron Microscopes: Use beams of electrons for much higher magnification and resolution than light microscopes.
Transmission Electron Microscope (TEM): Passes electrons through thin specimens, allowing visualization of internal structures up to 200,000X magnification.
Scanning Electron Microscope (SEM): Scans the surface of specimens with electrons, producing detailed 3D images of surfaces up to 100,000X magnification.
Example: TEM is used to study the internal structure of mitochondria, while SEM is used to visualize the surface of pollen grains.
Why Study Cells?
Understanding cells is crucial for advances in medicine and biology. The development of antibiotics, such as penicillin, revolutionized treatment of bacterial infections by targeting structures unique to bacterial cells.
Penicillin: Discovered in 1920, it drastically reduced deaths from bacterial infections.
Antibiotic Targets: Most antibiotics target bacterial ribosomes and enzymes, which differ from those in eukaryotic cells.
Antibiotic Resistance: Studying cells helps develop new antibiotics to combat resistant strains.
Example: Penicillin inhibits bacterial cell wall synthesis, which is absent in human cells.
Cell Size and Scale
Relative Sizes of Biological Structures
Cells and their components vary greatly in size, from visible structures to those requiring powerful microscopes.
Structure | Approximate Size | Visibility |
|---|---|---|
Human height | ~1.5-2 m | Naked eye |
Chicken egg | ~5 cm | Naked eye |
Plant and animal cells | 10-100 μm | Light microscope |
Nuclei, mitochondria, most bacteria | 1-10 μm | Light/electron microscope |
Viruses | 20-300 nm | Electron microscope |
Ribosomes | ~20 nm | Electron microscope |
Proteins, lipids | 1-10 nm | Electron microscope |
Atoms | ~0.1 nm | Not visible with current microscopes |
Measurement Equivalents
Understanding cell size requires familiarity with metric units:
1 meter (m) = 100 centimeters (cm) = 1,000 millimeters (mm) = micrometers (μm) = nanometers (nm)
1 centimeter (cm) = m = 10 mm
1 millimeter (mm) = m = cm
1 micrometer (μm) = m = mm
1 nanometer (nm) = m = μm
Example: A typical animal cell is about 20 μm in diameter, while a ribosome is about 20 nm.
Additional info: The notes cover foundational concepts in cell biology, including microscopy, antibiotic history, and cell size, which are essential for General Biology students.
