Microscopes

• What is a Light Microscope?

  An optical instrument that uses visible light and lenses to magnify and observe small objects or organisms, views living cells
• What is the max resoloution on a optical microscope?

  200 nm
• what is the max magnification on a optical microscope?

  1500
• What are the pros of a light microscope?

  Cheap, easy to use, can observe live cells.
• what are the cons of a light microscope?

  Limited resolution and magnification.
• How do electron microscopes work?

  Use beams of electrons instead of light → much higher resolution.
• what are the 2 types of electron microscopes?

  SEM & TEM
• How do Transmission Electron Microscopes work?

  Electrons pass through specimen → produces a high-resolution 2D image, allowing you to see internal cell structures like ribosomes & membranes.
• How do scanning electron microscopes work?

  Electrons bounce off the surface → produces a 3D image of the specimen, usually Used to study cell surfaces
• What is the max resoloution for TEM?

  0.1 nm (higher than light microscopes)
• What is the max resolution for SEM?

  1-10 nm
• Pros of TEM

  Highest resolution, detailed images of organelles.
• Pros of SEM

  Produces 3D images, great for surface details.
• Cons of TEM

  Expensive, specimens must be dead (vacuum required), complex preparation.
• Cons of SEM

  Lower resolution than TEM, requires a vacuum (dead specimens only).
• scientists struggled to distinguish cell organelles from other objects not part of the sample, what are they called?

  Artefacts, objects that are not part of the sample, such as air bubbles
• why is Cell Fractionation & Ultracentrifugation used?

  Its A technique used to separate organelles from a cell to study them individually.
• What are the steps of cell fractionation?

  Homogenization Filtration Ultracentrifugation
• What is the splitting of cells called?

  Fractionantion
• Explain Homogenisation

  Sample of cells are placed in cold, isotonic buffer soloution

  Then broken up using a homogeniser

  The results is a mixture of cell fragments, large and small
• Why must we use cold, isotonic buffer soloution?

  Buffer to maintain pH

  Cold to slow metabolic reactions

  isotonic to prevent organelles being damaged by osmosis
• What happens in filtration?

  Filter the fragments thorugh a gauze to remove large pieces of cell debris

  the filtrate is then centrifuged slowly

  After centrifugation, tube contains a pellet (solid) and supernatant (liquid above)
• What happens in ultracentrifugation?

  Nuclei are in the first pellet, the supernatant is then ultracentrifuged at high speed this time, each time the speed increases, pellet and supernatant are seperated each time
• What is the order of Organelle Separation (from heaviest to lightest)

  • Nucleus (most dense, first pellet).
  • Mitochondria & chloroplasts.
  • Lysosomes.
  • Endoplasmic reticulum (ER) & Golgi.
  • Ribosomes (smallest, last pellet).
• Why do we homogenise the cells?

  To break them open gently
• Whats the equation for magnification?

  Magnification = image size $\div$ actual image
• What does it mean by magnification?

  How many times bigger the image is
• What does it mean by resoloution?

  Ability to distingush 2 points as seperate