Investigating cells

• How do prokaryotic cells compare in size to eukaryotic cells?

  Prokaryotic cells are much smaller than eukaryotic cells
• How many centimeters are in 1 meter?

  100 centimeters
• How many millimeters are in 1 centimeter?

  10 millimeters
• What does the prefix "micro" mean?

  It means one millionth
• How many micrometers are in 1 meter?

  1,000,000 micrometers
• What is the typical size range of a human cell?

  Around 10 to 20 micrometers
• What does the prefix "nano" mean?

  It means one billionth
• How many nanometers are in 1 meter?

  1,000,000,000 nanometers
• What are the key prefixes used to describe sizes in biology?

  • Centi (1/100)
  • Milli (1/1000)
  • Micro (1/1,000,000)
  • Nano (1/1,000,000,000)
• How many millimeters are in a meter?

  1,000 millimeters
• What is the main part of the optical microscope where the slide is placed?

  The stage
• What is the function of the clips on the stage of the microscope?

  To hold the microscope slide in place
• What is located below the stage of the optical microscope?

  A lamp or a mirror
• How does the lamp function in an optical microscope?

  It passes light up through the microscope slide
• What is the purpose of the objective lenses in an optical microscope?

  To magnify the image of the specimen
• How many objective lenses do most optical microscopes have?

  Three
• What are the typical magnifications of the objective lenses?

  Four times, ten times, or forty times
• What is the magnification of the eyepiece lens?

  Ten times
• What are the two focusing dials on the microscope used for?

  To adjust the focus of the image
• What is the first step in using an optical microscope to view a prepared slide?

  Place the slide onto the stage and use the clips to hold it in place
• Why is it important to select the lowest power objective lens first?

  To avoid damaging the slide while focusing
• How do you position the objective lens when using the microscope?

  Turn the coarse focusing dial until it almost touches the slide
• What should you do while adjusting the position of the objective lens?

  Look at the microscope from the side
• What should you do after positioning the objective lens?

  Look down through the eyepiece and slowly turn the coarse focusing dial
• What is the purpose of the fine focusing dial?

  To bring the cells into clear focus
• How do you calculate the total magnification of the microscope?

  Multiply the magnification of the eyepiece lens by the magnification of the objective lens
• What is the total magnification when using a ten times eyepiece lens and a four times objective lens?

  Forty times
• What should you do after achieving focus with the low-power objective lens?

  Select a higher power objective lens and adjust the fine focusing dial
• What can you typically see when viewing animal cells under an optical microscope?

  The nucleus, cytoplasm, and cell membrane
• What additional structures can be seen in plant cells under an optical microscope?

  The cell wall, vacuole, and chloroplasts
• How should you include a magnification scale in your drawing of cells?

  Place a clear plastic ruler over the stage and measure the diameter of the field of view
• What are the key steps to using an optical microscope to view a prepared slide?

  1. Place the slide on the stage and secure it with clips.
  2. Select the lowest power objective lens.
  3. Position the objective lens close to the slide using the coarse focusing dial.
  4. Look through the eyepiece and adjust the coarse focusing dial until the cells come into focus.
  5. Use the fine focusing dial for a clearer focus.
  6. Calculate total magnification by multiplying eyepiece and objective lens magnifications.
  7. Optionally switch to a higher power objective lens and refocus.
  8. Draw and label the cells, including a magnification scale.
• What are the limitations of viewing cells with an optical microscope?

  • Limited detail visible (e.g., cannot see ribosomes)
  • Dependent on the type of cell being viewed
  • Cannot view live cells in detail
• What are the main parts of an optical microscope?

  • Stage
  • Clips
  • Lamp or mirror
  • Objective lenses
  • Eyepiece lens
  • Coarse focusing dial
  • Fine focusing dial
• What are the two main problems with light microscopes?

  Limited magnification and limited resolution
• Why can't we easily view structures inside the nucleus with a light microscope?

  Because the magnification is not powerful enough
• What does limited resolution mean for light microscopes?

  It means the image is blurred, even at higher magnification
• What invention did scientists create to explore structures inside cells in detail?

  The electron microscope
• What are the key advantages of electron microscopes compared to light microscopes?

  They have much greater magnification and resolution
• How can we calculate the magnification of a microscope?

  By using the equation: magnification = size of the image / size of the real object