Methods of studying cells

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  • Created by: Hindleyc
  • Created on: 02-03-18 10:48
What is Magnification?
How much bigger we can make something appear- ratio of image size to object size
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What is resolution?
How much better we can distinguish two closely spaced points- Ability to distinguish 2 separate points that are close together
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How does a Light (optical) microscope work?
Use visible light and a system of lenses to magnify images
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How do Electron microscopes work?
Uses a beam of electrons focused by magnets
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How does a Transmission electron microscope work?
Transmits a beam of electrons through a specimen to look at internal structures
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How does a scanning electron microscope work?
Scan a specimen with a beam of electrons to look at the surface and internal structures - electrons bounce off surface of specimen
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Why can electron microscopes have a higher magnification and resolution?
Electrons have a smaller wavelength than light so a beam of electrons can have increased magnification and resolution
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What does a light microscope use? how does it focus? what is the magnification size like? resolution?
Light beam, glass lenses focus, quite small (1000-1500x), 200nm (quite low)
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What can the specimen be in a light microscope? Is fixing and staining possible? Price?
Alive, possible if specimen dead, equipment relative inexpensive
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What does a TEM use? focus? magnification? resolution?
Electron beam, electromagnets focus, Large (500,000x), less than 1nm (higher)
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What must the specimen be? Fixing and staining? price? vacuum? colour?
Dead and thin, must be- coated with heavy metal that is electron dense that takes a while to prepare, v expensive and yes, black and white
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What does a SEM use? Focus? magnification? Resolution?
Electron beam, Electromagnets focus, Large (200,000) Lower- 10-2 nm
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What must the specimen be? what is it coated with and why? price? what can image be- by using what? colour?
Dead and solid- not just thin, metal to reflect, equipment v expensive, use computers to produce 3D image, coloured
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What are artefacts?
Features in images that are not present in specimen but rather are due to processes used to prepare specimen and produce image
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What may introduce artefacts into images?
Complex staining processes
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What causes differences in images?
The way the cell was sliced
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What can be used to identify starch grains in plant cells?
Iodine in potassium iodide solution
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What is 1mm?
1000 micrometres
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What is 1 micrometer
1000 nano meters
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What is magnification equation?
Image size / actual size (MIA)
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What are the separated components from cell fractionation and ultracentrifugation used for?
Analyse comments chemically. Microscope examination with SEM&TEM. Physiological investigation.
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What does cell fractionation do?
Disrupts cell membranes and wall and releases the organelles creating a soup of organelles
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What is step 1
Before fractionation cells placed in cold, isotopic buffered solution
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Why cold?
Prevents enzyme activity such as damage by enzymes- breaking down cells
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Why isotonic?
Prevent osmotic damage eg swelling or shrinking
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Why buffered?
Maintain constant PH to prevent damaging PH change
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What is step 2?
Homogenise using ultrasound or grind open in a blender-break open membrane release organelles
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Why does it need filtering? (step 3)
To remove cell debris and unbroken cells so it doesn't contaminate the sample/ affect the results
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What is step 4
Ultrafugation-Spin filtrate in a centrifuge
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Why do we spin?
Creates super-gravitational field that causes organelles to separate according to their density
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What does it spin at first? What contains the rest?
Low speed to separate the nuclei into a pellet, Supernatent
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What is step 5?
Remove liquid and re-spin at a higher speed to separate next densest organelle- mitochondria.
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What happens if you increase the speed after the mitochondria?
Lysosomes, ER, Ribosomes
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How do bacteria reproduce? rate? how?
Binary fission. Rapid 10 mins. Cell splits in half
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How does it work?
Replication of circular DNA and plasmids. Division of cytoplasm to produce 2 daughter cells, each with single copy of circular DNA and variable number or copies of plasmids
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What don't viruses undergo? Why? how?
Cell division as non-living. Injection of Nucleic acids into host cell, infected host cell replicates the virus particles
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How does it work?
Only reproduce by entering host cell and taking over some of cells organelles using to make more virus particles
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What are all viruses composed of? What do the genes in the nucleic acids contain?
Protein capsules that surrounds some nucleic acid- DNA/RNA. Information for making new virus particle
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What happens once complete?
New virus particles burst out of cell and can re-infect new cells
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Other cards in this set

Card 2

Front

What is resolution?

Back

How much better we can distinguish two closely spaced points- Ability to distinguish 2 separate points that are close together

Card 3

Front

How does a Light (optical) microscope work?

Back

Preview of the front of card 3

Card 4

Front

How do Electron microscopes work?

Back

Preview of the front of card 4

Card 5

Front

How does a Transmission electron microscope work?

Back

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