REQUIRED PRACTICALS

• 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 an optical microscope?


  A lamp or a mirror
• How does a mirror function in some optical microscopes?


  It reflects light up through the microscope slide
• What are the lenses above the stage called?


  Objective lenses
• How many objective lenses do most microscopes have, and what are their typical magnifications?


  Three objective lenses with magnifications of four times, ten times, and forty times
• What is the magnification of the eyepiece lens?


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


  The coarse focusing dial and the fine focusing dial
• 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
• Which objective lens should be selected first when viewing a slide?


  The lowest power objective lens, usually four times
• How do you position the objective lens when starting to view a slide?


  Position it so it almost touches the microscope slide
• Why is it important to look at the microscope from the side while adjusting the objective lens?


  To avoid damaging the slide
• What should you do after positioning the objective lens close to the slide?


  Look down through the eyepiece and slowly turn the coarse focusing dial
• What process do bacteria use to reproduce?


  Bacteria reproduce by binary fission
• What is the purpose of the fine focusing dial?


  To bring the cells into a clear focus
• Under ideal conditions, how often can bacteria double in number?


  Every 20 minutes
• What is a nutrient broth solution used for?


  It contains all the nutrients that bacteria need to grow and divide
• How do you calculate the total magnification of the microscope?


  Multiply the magnification of the eyepiece lens by the magnification of the objective lens
• Why does the broth appear cloudy?

  Because it contains a very large number of bacteria
• What is the total magnification when using a ten times eyepiece lens and a four times objective lens?


  $40 \text{ times}$
• What is an agar gel plate?


  Agar gel plates contain nutrient broth that has been solidified into a jelly using agar
• 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 again
• What is the importance of avoiding contamination when preparing bacterial cultures?


  To ensure that only the desired bacteria grow in the culture
• What can be seen when looking at animal cells under an optical microscope?

  The nucleons, cytoplasm, and cell membrane
• What is the first step in avoiding contamination when preparing cultures?


  Carefully sterilize the petri dishes, bacterial nutrient broth, and agar
• What additional structures might be visible in plant cells under an optical microscope?

  The cell wall, cytoplasm, nucleus, vacuole, and chloroplasts
• How is an inoculating loop sterilized before use?


  By passing it through a flame, such as a Bunsen burner
• What should you include in your drawing of cells observed under the microscope?


  A clear label drawing and a magnification scale
• How do you create a magnification scale for your drawing?


  Measure the diameter of the field of view in millimeters and show this on the drawing using a scale bar
• What should you write on your drawing besides the scale?

  The magnification, for example, 100 times
• Why do we attach the lid of the petri dish with adhesive tape?


  To stop the lid from falling off and prevent contamination
• What is the purpose of the optical microscope in biology?


  To view cells and their structures
• At what temperature do we normally incubate bacteria in schools?

  25 degrees Celsius
• What limitations does an optical microscope have in viewing details of cells?


  It can only see limited detail, such as nucleons, cytoplasm, and cell membrane
• Why is it important to incubate the agar plate upside down?


  To prevent moisture from dripping down and disrupting the colonies
• What is the purpose of using a sterile agar gel plate in the investigation of antibiotics?


  To ensure that no other microorganisms interfere with the results
• How does the visibility of structures differ between animal and plant cells under an optical microscope?


  Animal cells show nucleons and cytoplasm, while plant cells show cell wall and chloroplasts
• What might you see in the cytoplasm of animal cells under an optical microscope?


  Tiny flecks that may be mitochondria
• What is osmosis?


  Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
• What is the zone of inhibition?


  A region where bacteria do not grow around the antibiotic disc