2.1.2 Using a Microscope

• Why are optical microscopes important for scientists?

  They allow for tissues, cells, and organelles to be seen and studied
• What biological process can be observed using a microscope?

  The movement of chromosomes during mitosis
• How does light pass through a microscope slide?

  Light is directed through the thin layer of biological material on a glass slide
• What increases the magnifying power of a microscope?

  Rotating the higher power objective lens into place
• What are the key components of an optical microscope?

  • Eyepiece lens
  • Objective lenses
  • Stage
  • Light source
  • Coarse and fine focus
• What other tools are used in microscopy?

  • Forceps
  • Scissors
  • Scalpel
  • Coverslip
  • Slides
  • Pipette
  • Staining solution
• What is the purpose of the coarse focus in a microscope?

  It is used to focus the low- and medium-power objective lenses
• What is the function of the fine focus in a microscope?

  It is used to focus the high-power objective lens
• What should be done when preparing a slide using a liquid specimen?

  Add a few drops of the sample to the slide and cover it with a coverslip
• Why is it important to wear gloves when preparing microscope slides?

  To ensure there is no cross-contamination of foreign cells
• Why must the tissue be thin when preparing a microscope slide?

  So that the light from the microscope can pass through
• What is the first step when preparing a slide using a solid specimen?

  Use scissors to cut a small sample of the tissue
• What is the purpose of applying a stain to a specimen?

  To enhance visibility of the structures within the specimen
• What is the process of fixing a specimen for microscopy?

  Using formaldehyde to preserve and make the tissue rigid
• What is the purpose of dehydrating a specimen using ethanol solutions?

  To remove water and prepare the specimen for embedding
• What is a microtome used for?

  To cut thin slices from the specimen
• What is the purpose of a coverslip in microscopy?

  To protect the specimen and reduce air bubbles
• What should be done to prevent dehydration of tissue on a slide?

  Add a drop of water to the specimen beneath the coverslip
• What should you do if the image is unclear or blurry?

  Switch to the lower power objective lens and use the coarse focus
• What is a graticule used for in microscopy?

  To take measurements of cells in the field of view
• Why must a graticule be calibrated?

  Because it has no fixed units and must match the objective lens in use
• What is a limitation of optical microscopes compared to other types of microscopes?

  They do not have the same magnification power
• What can cause inconsistencies in the size of cells or structures viewed on slides?

  Different tissue samples being cut at different planes
• How can the treatment of specimens affect microscopy results?

  It could alter the structure of cells
• What is the purpose of staining in light microscopy?

  To make the tissue colored and visible
• What is differential staining?

  Staining specimens with multiple dyes to show different tissues
• Why are colored dyes used when staining specimens?

  They absorb specific colors of light while reflecting others
• Which tissues do not require staining to be visible?

  Chloroplasts
• What color does toluidine blue stain cells?

  Blue
• What color does phloroglucinol stain cells?

  Red/Pink
• Why must specimens be stained for transmission electron microscopy (TEM)?

  To absorb electrons since they have no color
• What types of compounds are commonly used as dyes for electron microscopy?

  Heavy-metal compounds
• How is color added to electron micrographs?

  Using image-processing software
• What can be seen using a transmission electron microscope (TEM)?

  The internal structure of the mitochondrion
• What is a spiracle?

  A structure found on the exoskeleton of an insect