Cell structure and transport

• What is the relationship between kilometres and metres?

  1 kilometre = 1000 metres
• How many centimetres are in a metre?

  1 metre = 100 centimetres
• How many millimetres are in a centimetre?

  1 centimetre = 10 millimetres
• How many micrometres are in a millimetre?

  1 millimetre = 1000 micrometres
• How many nanometres are in a micrometre?

  1 micrometre = 1000 nanometres
• What is the standard form of one nanometre in metres?

  1 nanometre = $1 \times 10^{-9} \text{ m}$
• When were the first light microscopes developed?

  In the mid-17th century
• What is the primary function of light microscopes?

  To look at cells and form images
• What is the maximum magnification of the best light microscopes?

  About 2000 times
• Why are light microscopes widely used?

  They are cheap and can magnify live specimens
• When was the electron microscope invented?

  In the 1930s
• What do electron microscopes use to form images?

  A beam of electrons
• What is the maximum magnification of electron microscopes?

  Up to around 2000000 times
• What type of images do transmission electron microscopes produce?

  2D images with high magnification
• What type of images do scanning electron microscopes produce?

  3D images with lower magnifications
• What are the requirements for using electron microscopes?

  Special temperature, pressure, and humidity control
• How do you calculate magnification using a light microscope?

  Multiply eyepiece magnification by objective magnification
• If the eyepiece lens is x4 and the objective lens is x10, what is the overall magnification?

  $40 \text{ times}$
• What should you include when labeling microscope drawings?

  • Indicate the magnification used
  • Specify the magnification at which the specimen was viewed
• What is the formula to calculate the size of an object under a microscope?

  magnification = size of image / size of real object
• How can you find the size of an object if you know two factors?

  You can calculate the third factor using the formula
• If the magnification is x40 and the image size is 1 mm, what is the size of the real object?

  0.025 mm or 25 µm
• What is the resolving power of a light microscope?

  About 200 nm
• What is the resolving power of a scanning electron microscope?

  About 10 nm
• What is the resolving power of a transmission electron microscope?

  About 0.2 nm
• Why are microscopes useful?

  They magnify objects, making them appear larger
• How does the magnification of an electron microscope compare to a light microscope?

  Electron microscopes can magnify much more
• What happens if two objects are closer than the minimum distance for resolution?

  They appear as one object
• What is resolution in microscopy?

  • Ability to distinguish between two separate points
  • Affects the detail visible in the image
• What are the steps to calculate the size of a cell using magnification?

  1. Measure the size of the image
  2. Know the magnification level
  3. Use the formula: size of real object = size of image / magnification
• What are the magnification heights for an average person using different microscopes?

  • Light microscope: about 3.5 km
  • Electron microscope: about 3500 km
• What are the links to further study mentioned in the material?

  • Maths section in Topic M1b for standard form
  • Chapter B2 for cell structure