Biology

• What is the function of the eyepiece lens in a light microscope?


  This is the lens closest to your eye, usually with a magnification of x10.
• What is the purpose of the objective lens in a light microscope?


  It has three lenses of different strengths to magnify the image more clearly.
• How does the diaphragm function in a light microscope?


  It controls the amount of light that goes onto the microscope slide.
• What is the role of the stage in a light microscope?


  It is the place where you put a microscope slide.
• What is the function of the light source in a light microscope?


  It projects light onto the microscope slide, which can be a mirror or an electric bulb.
• What is the purpose of the base in a light microscope?


  It is very heavy to keep the microscope from falling over.
• What is the function of the fine focus knob in a light microscope?


  It is used to focus the image so it is very sharp and clear.
• What is the function of the coarse focus knob in a light microscope?


  It is used to focus the image so that you can see it clearly.
• What are the key differences between magnification and resolution?

  • Magnification: how many times bigger the image is compared to the object.
  • Resolution: minimum distance apart two objects can be for them to appear separate.
• What is the resolution limit of light microscopes?


  Light microscope resolution is 0.2 µm.
• What happens if two objects are less than 0.2 µm apart under a light microscope?


  They will not be seen separately.
• What is the effect of increasing magnification beyond the limit of resolution?


  It will result in a larger but blurrier image.
• What are the characteristics of prokaryotic cells?


  • Smaller than eukaryotic cells (0.2-2 µm compared to 10-100 µm)
  • No nucleus; single circular DNA molecule free in cytoplasm
  • Cytoplasm with no membrane-bound organelles
  • Smaller ribosomes (70S)
  • Peptidoglycan cell wall
  • May contain plasmids, capsule, and flagella
• What are the guidelines for biological drawings?


  1. Use a sharp pencil
  2. Draw smooth, continuous lines (no sketching)
  3. No shading
  4. Label with straight lines (no overlapping labels)
  5. Include title with specimen name and magnification
• What is the first number in standard form always between?


  1 and 9.9
• How is a number in standard form written?


  With a times to the power of 10
• What does a positive power of 10 indicate about a number in standard form?


  The number is bigger than 1
• What does a negative power of 10 indicate about a number in standard form?


  The number is smaller than 1
• What units are commonly used when discussing cells?


  Millimetres, micrometres, and nanometres
• How do you convert 30 cm to nanometres?


  30 cm = 3 x 10⁸ nm
• What is the purpose of the graticule in microscopy?


  • It is placed into the eyepiece of the microscope
  • It is 1 mm long, divided into 100 divisions
  • Used to measure specimens accurately
• What is the process to calibrate the eyepiece graticule using a stage micrometer?


  1. Align the micrometer and eyepiece graticule
  2. Count divisions on the eyepiece corresponding to micrometer divisions
  3. Calculate the size of one eyepiece division
  4. Measure the specimen
• What is the length of the stage micrometer?


  1 mm
• How many divisions are in the stage micrometer?


  100 divisions
• What is the formula for magnification?


  Magnification = Image Size / Actual Image
• If a cell has a tail 50 µm long, how would you express this in terms of magnification?


  Magnification = Image Size / Actual Image
• Who invented Gram staining and in what year?

  Christian Gram in 1884
• What is the first step in the Gram staining process?


  Application of crystal violet
• What role does iodine play in Gram staining?


  Iodine is a stain that is a larger molecule
• What is the function of alcohol in the Gram staining process?


  It dehydrates the outer layer allowing movement of molecules
• What is the final step in the Gram staining process?


  Application of safranin
• What characterizes Gram positive bacteria?


  They have a thick cell wall that retains the stain
• Why do Gram negative bacteria not retain the crystal violet stain?


  They have a thin peptidoglycan cell wall
• What is the structure of Gram negative bacteria?


  They have a thin cell wall and two cell membranes
• What is the significance of the outer membrane in Gram negative bacteria?


  It prevents certain drugs and antibiotics from entering the cell
• What types of infections are commonly caused by Gram negative bacteria?


  Pneumonia and meningitis
• What is cell differentiation?


  • The process in which a less specialised cell develops into a more specialised form
  • Allows cells to perform specific functions
• Why are there approximately 200 different types of cells in the human body?


  • Each cell is adapted to perform a specific function
  • Reflects levels of organisation in multicellular organisms
• What is the function of palisade mesophyll cells?


  To absorb a large amount of light for photosynthesis
• How do palisade mesophyll cells maximize light absorption?


  They move around the cytoplasm