Studying cells, microscopy

• Microscopy techniques

  • Unaided eye
  • Light microscopy
  • Electron microscopy
  • Super-resolution microscopy
• Length of some nerve and muscle cells is around 1 cm
• Most plant and animal cells are around 10 µm
• Nucleus is around 1 µm
• Most bacteria are around 1 µm
• Mitochondrion is around 100 nm
• Smallest bacteria are around 10 nm
• Viruses are around 1 nm
• Ribosomes are around 0.1 nm
• Microscopic structures

  • Proteins
  • Lipids
  • Small molecules
  • Atoms
• Microscopy principles include lamp, lens, eyepiece, and sample holder
• van Leeuwenhoek microscope

  Included focus knob, sample holder, and lens. He made over 500 lenses and could magnify up to 500x.
• Robert Hooke: '"I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular ... these pores, or cells, .... were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this."'
• Robert Hooke used a microscope he built himself to examine the structure of various objects including cork. This was the first observation and description of cells.
• van Leeuwenhoek described the first single-celled organisms and therefore the first live cells in 1674.
• van Leeuwenhoek: '"In the year of 1675 I difcover'd living creatures in Rain water…."'
• van Leeuwenhoek: '"I then most always saw, with great wonder, that in the said matter there were many very little living animalcules, very prettily a-moving. The biggest sort. . . had a very strong and swift motion, and shot through the water (or spittle) like a pike does through the water. The second sort. . . oft-times spun round like a top. . . and these were far more in number."'
• van Leeuwenhoek discovered sperm, described red blood cells, and discovered bacteria in 1676.
• Standard light microscopy techniques

  • Bright-field microscopy
  • Phase contrast microscopy
  • Differential Interference Contrast (DIC) microscopy
• Azan trichrome stain

  Nuclei are stained bright red, collagen/basement membrane/mucin are stained blue, muscle and red blood cells are stained orange to red. Good for staining connective tissue and epithelium.
• Hematoxylin & Eosin stain

  Most commonly used stain in histology. Hematoxylin (purple) stains acidic structures like nucleus, Eosin (pink) stains basic structures like cytoplasm and cell walls.
• In 1878 Walther Flemming deciphered the major stages of mitosis using newly developed dyes like aniline to visualise chromosomes. He invented the terms mitosis and chromatin.
• Fluorescence

  Glows when light is reflected, blocks red and green, varies due to stains/dyes used, reflects unnecessary wavelengths and passes necessary wavelengths through 2nd barrier filter
• Transmission electron microscope uses electromagnets, scanning electron microscope uses light reflecting off specimen
• Scanning electron microscopy provides high resolution images of cell surfaces
• Transmission electron microscopy provides the highest resolution possible and uses antibodies labelled with gold to detect cellular structures
• Resolution

  The clarity of the image, or the minimum distance of two distinguishable points. Magnification is just how much larger the image is compared to its real size.