bio paper 1 required practicals

• What is the main part of the optical microscope where the slide is placed?

  The stage
• What is the function of the lamp in an optical microscope?

  To illuminate the microscope slide
• What is used in some optical microscopes instead of a lamp?

  A mirror
• What are the objective lenses used for in an optical microscope?

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

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

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

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

  Coarse and fine focusing dials
• What is the first step to use an optical microscope?

  Place the slide onto the stage
• What should you do after placing the slide on the stage?

  Select the lowest power objective lens
• How do you position the objective lens when starting?

  Almost touch the microscope slide
• What should you be able to describe by the end of the video?

  Investigate the effect of osmosis on plant tissue
• What is osmosis?

  Diffusion of water through a membrane
• Why should you look at the microscope from the side while adjusting?

  To avoid damaging the slide
• What happens to plant cells in water?

  Water moves in, causing cells to expand
• What do you do after the objective lens is positioned?

  Look through the eyepiece and adjust
• What happens to plant cells in a concentrated solution?

  Water moves out, causing cells to shrink
• What is the purpose of the fine focusing dial?

  To bring the cells into clear focus
• What vegetable is commonly used to investigate osmosis?

  Potato
• How do you calculate the total magnification?

  Multiply eyepiece magnification by objective magnification
• Why do we peel the potato before the experiment?

  The skin can affect osmosis
• What tool is used to produce potato cylinders?

  Cork borer
• Why do we trim the potato cylinders to the same length?

  To ensure consistent measurement of osmosis
• What is the total magnification when using a ten times eyepiece and a four times objective lens?

  Forty times
• What is a good length for the potato cylinders?

  About three centimeters
• What should you do after selecting a higher power objective lens?

  Adjust the fine focusing dial again
• What do we measure before placing the cylinders in the solution?

  The length and mass of each cylinder
• What can you see when looking at animal cells under an optical microscope?

  Nucleus, cytoplasm, and cell membrane
• How much of a 0.5 molar sugar solution is added to the first test tube?

  10 centimeters cubed
• What additional structures can be seen in plant cells?

  Cell wall, vacuole, and chloroplasts
• Why do we use distilled water instead of tap water?

  Distilled water has no dissolved substances
• How do you include a magnification scale in your drawing?

  Measure the diameter of the field of view
• What should we do after leaving the potato cylinders overnight?

  Gently roll them on paper towel
• Why is it important not to press on the cylinders?

  To avoid forcing water out of the cells
• What should you write on your drawing besides the scale?

  The magnification
• What do we measure again after removing the potato cylinders?

  The length and mass of the cylinders
• What is the formula for calculating percentage change?

  Percentage change = (change in value / original value) × 100
• What are the steps to use an optical microscope to view a prepared slide?

  1. Place the slide on the stage and secure it.
  2. Select the lowest power objective lens.
  3. Position the objective lens close to the slide.
  4. Look through the eyepiece and adjust the coarse focusing dial.
  5. Use the fine focusing dial for clear focus.
  6. Calculate total magnification.
  7. Optionally switch to a higher power objective lens.
  8. Draw and label the observed cells.
• If a potato cylinder has a starting mass of 1.56 grams and increases by 0.25 grams, what is the percentage change?

  +16.03 percent
• What are the limitations of viewing cells with an optical microscope?

  • Limited detail visible
  • Cannot see organelles like ribosomes
  • Dependent on the type of cell observed