Cell Structure

• What is the first step in preparing a temporary mount of tissue for a light microscope?

  Obtain a thin section of tissue using an ultratome or by maceration.
• What should a student do after placing plant tissue in a drop of water?

  Stain the tissue on a slide to make structures visible.
• Why is it important to add a coverslip at a 45° angle when preparing a temporary mount?

  To avoid trapping air bubbles.
• How do light microscopes work in terms of light rays?

  Lenses focus rays of light and magnify the view of a thin slice of specimen.
• What happens to different structures in a specimen when viewed under a light microscope?

  Different structures absorb different amounts and wavelengths of light.
• How is reflected light transmitted to the observer in a light microscope?

  Reflected light is transmitted via the objective lens and eyepiece.
• What is the first step in how a transmission electron microscope (TEM) works?

  Pass a high energy beam of electrons through a thin slice of specimen.
• Why do more dense structures appear darker in a TEM image?

  Because they absorb more electrons.
• How is the image focused in a TEM?

  The image is focused onto a fluorescent screen or photographic plate using magnetic lenses.
• What is the first step in how a scanning electron microscope (SEM) works?

  Focus a beam of electrons onto a specimen’s surface using electromagnetic lenses.
• What happens to the reflected electrons in a SEM?

  Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate.
• What is the first step in how a laser scanning confocal microscope works?

  Focus a laser beam onto a small area on a sample’s surface using objective lenses.
• What do fluorophores in the sample do in a laser scanning confocal microscope?

  Fluorophores emit photons when excited by the laser beam.
• How is the image produced in a laser scanning confocal microscope?

  An image is produced pixel by pixel in the correct order by amplifying the signal onto a detector.
• How should the field of view in microscopy be recorded?

  Draw a diagram with a sharp pencil, include a scale bar, and annotate visible structures.
• What is the equation to calculate the actual size of a structure from microscopy?

  Actual size = image size / magnification
• What is magnification in microscopy?


  Magnification is the factor by which the image is larger than the actual specimen.
• What is resolution in microscopy?


  Resolution is the smallest separation distance at which two separate structures can be distinguished from one another.
• Why do samples need to be stained for light microscopes?

  Coloured dye binds to the structures, facilitating absorption of wavelengths of light to produce an image.
• What is the magnification and resolution of a compound light microscope?

  Magnification: x 2000, Resolution: 200 nm