Biology (cell biology)

• What does a light microscope use to magnify objects?

  Light waves and lenses
• How do you calculate the actual size of a cell?

  Actual size = Image size ÷ Magnification
• If a cell viewed at x100 magnification has a diameter of 1 cm, what is its real diameter?

  0.01 cm or 100 μm
• What are the steps to mount a specimen on a slide for a light microscope?

  1. Place a drop of water on the slide.
  2. Position the specimen on the liquid.
  3. Place a cover slip at an angle.
  4. Remove excess water with a paper towel.
  5. Optionally add a stain to highlight parts.
• Why is it important to avoid air bubbles when placing a cover slip?

  Air bubbles can obstruct the view
• What is the first step in using a light microscope?

  Turn the nose piece to select the lowest power lens
• What should you do after bringing the specimen into focus?

  Add labels to the prepared sketch
• What are the two main types of cells?

  Prokaryotic and eukaryotic
• What is a characteristic of prokaryotic cells?

  Genetic material is not enclosed in a nucleus
• What is chromosomal DNA in prokaryotic cells?

  A long loop of DNA attached to a mesosome
• What is the function of ribosomes in prokaryotic cells?

  They synthesize proteins
• How do prokaryotes multiply?

  By binary fission
• What is the average division time for bacteria?

  The time it takes for one bacterium to divide
• If a bacterium divides every 20 minutes, how large will the population be after 4 hours?

  4,096 or 4.096 x 10³
• What are the two main types of culture medium for growing microorganisms?

  • Broth: Liquid medium for even distribution
  • Agar: Solid medium in Petri dishes
• Why must aseptic techniques be used when handling culture media?

  To prevent contamination
• What indicates the effectiveness of an antiseptic or antibiotic?

  The area of the inhibition zone
• How does diffusion occur?

  Particles spread from high to low concentration
• What are the features of specialised exchange surfaces in multicellular organisms?

  1. Large surface area for rapid exchange
  2. Thin walls for short distance travel
  3. Good blood supply for steep concentration gradient
• How do fish gills facilitate gas exchange?

  They have a large surface area and thin walls
• What is the formula for percentage change in mass?

  Percentage change = Change in mass x 100 ÷ Initial mass