Unlock the Mysteries of Cell Biology with Our Ultimate Study Notes!
Dive into the essentials of cellular evolution and differentiation with our expertly crafted notes. Perfect for students, educators, and curious minds, these notes offer:
In-Depth Insights: From the theory of endosymbiosis t...
● Purpose: Microscopes magnify objects too small to be seen with the naked
eye, revealing details about small structures and microorganisms.
● History:
○ 17th Century: The first microscopes were developed.
○ Pioneers: Robert Hooke and Antoni van Leeuwenhoek discovered
microorganisms using light microscopes.
○ Magnification: Light microscopes can magnify objects by 10–400
times their actual size.
Types of Microscopes:
● Light Microscopes (Compound Microscopes): Use lenses and light to
magnify objects.
● Electron Microscopes: Use beams of electrons to create highly detailed
images (covered in later sections).
Microscopy in Practice:
● Specimens: Objects viewed under a microscope.
● Focusing:
1. Start with the lowest magnification and highest stage position.
2. Use the coarse focus knob to adjust distance between the specimen
and lens.
3. Use the fine focus knob for precise adjustments.
4. Adjust magnification by rotating the nosepiece to select a different
objective lens.
Cell Theory:
● Spontaneous Generation: The outdated belief that life could arise from
non-living matter.
● Development:
○ 1665: Robert Hooke discovered non-living cork cells.
○ 1674: Antoni van Leeuwenhoek observed living cells.
○ 1838-1839: Matthias Schleiden and Theodor Schwann compared plant
and animal cells, leading to cell theory.
○ 1858: Rudolf Virchow stated "all cells come from cells."
Making Temporary (Wet) Mounts:
, ● Steps:
1. Cut a small square of onion tissue.
2. Peel off a thin layer with tweezers.
3. Place the layer on a glass slide and add a drop of iodine.
4. Lower a cover slip over the specimen to avoid bubbles.
● Staining: Iodine is used for plant cells; methylene blue is used for animal
cells.
● Eyepiece Graticule & Stage Micrometer:
○ Eyepiece graticules contain a scale to measure specimens.
○ Stage micrometers are calibrated rulers used to calibrate the graticule.
● Unit Conversions:
○ 1 millimeter (mm) = 1000 micrometers (μm).
○ 1 micrometer (μm) = 1000 nanometers (nm).
● Magnification Calculations: Use the formula:
○ Magnification = Image Size / Actual Size
By mastering these concepts, you'll enhance your understanding of microscopy and
cell theory, which are foundational to biology and many scientific disciplines.
● Usage: Common in schools, these microscopes pass light through a specimen
and use lenses to magnify the image.
● Limitation: Cannot resolve structures smaller than 200 nanometers (nm),
limiting the visualization of tiny cellular components.
Electron Microscopy:
● How It Works:
○ Electron Beam: Instead of light, a beam of electrons passes through
the specimen.
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