Microscope & Culturing Notes

Microscopes

  • Magnification Definition: Measures how many times larger an image appears compared to the real object.
    • Enlarged if magnification is greater than 11.
    • Reduced if magnification is less than 11.
  • Magnification Formula:

M=Image SizeActual SizeM = \frac{\text{Image Size}}{\text{Actual Size}}

  • Unit Conversions:
    • 1 mm=1000 μm1\,\text{mm} = 1000\,\mu\text{m}
    • 1 μm=1000 nm1\,\mu\text{m} = 1000\,\text{nm}
  • Electron Microscopes: Offer higher magnification and resolution compared to light microscopes, providing clear images of subcellular structures.

Culturing

  • Binary Fission: Bacteria reproduce via cell division known as binary fission (unlike plants and animals, which undergo mitosis).
  • Reproduction Rate: Can divide as often as every 20 minutes20\,\text{minutes} when provided with nutrients in broth or agar at an appropriate temperature.
  • Testing Requirements: Uncontaminated cultures are required to accurately test the effects of disinfectants or antibiotics.
  • Contamination Control:
    • Sterilise petri dishes and culture media using heat or radiation.
    • Sterilise the inoculating loop by passing it through a flame.
    • Tape the lid of the petri dish securely without completely sealing it around, allowing oxygen to flow.
    • Incubate cultures at a maximum temperature of 25 ∘C25\,^\circ\text{C} in school laboratories to prevent the growth of human pathogens.
  • Antiseptics: Function to destroy bacteria.