Biology F211

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  • Created by: Cake4Bant
  • Created on: 07-05-15 20:53
Light Microscope Magnification
x1500
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What is Magnification?
The degree in which the size of an image is larger than itself.
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What is Resolution?
The degree in which it is possible to distinguish between two objects that are very close together. Particles can be seen as separate objects if they are further apart than the wavelength of light.
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What is staining?
Coloured chemicals that bind to the chemicals on or in the specimen, Allows the specimen to be seen.
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What is sectioning?
Specimens are imbedded in wax. Thin sections are then cut without distorting the structure of the specimen. This is particularly useful for making sections of soft tissue, such as brain.
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3 main limits of resolution
Human eye - 100um / Light microscope - 200nm / Electron microscope - 0.20nm
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Actual size =
Image Size/ Magnification
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Transmission Electron Microscope (TEM)
The electron beam passes through a very tiny prepared sample. Electrons pass less easily through denser parts of the cell, this adds contrast. The final image produced is 2D, magnification is x500 000
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Scanning Electron Microscope (SEM)
The electron beam is directed onto sample (Doesn't pass through), They're bounced ff the sample. Final image produced is a 3D view of the surface of the sample, magnification is x100 000.
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Advantages of electron microscopes
The resolution is 0.2nm (1000x smaller than a light microscope). Used to produce detailed images of the structures (organelles) inside cells. SEM's allow us to see contours of cellular or tissue arrangements.
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Disadvantages of Electron Microscopes
Electron beams are deflected by the molecules in the air, so samples have to be placed in a vacuum. They are extremely expensive and preparing samples and using the electron microscope both require a high degree of skill and training.
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Coloured Electron Micrographs
Original SEM's produced in black and white, however images receive colour from false colouring.
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Seven Characteristics of all living organisms:
Movement, Growth, Respiration, Sensitivity, Nutrition, Excretion and Reproduction.
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Division of Labour
Different organelles working together, each contributing its part to the survival of the cell.
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Cytoskeleton
A network of fibres made of protein, used to keep the cell shape stable by providing an internal framework.
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Microtubules
Cylinders about 25nm in diameter, made of the protein tubulin. Used to move micro-organisms through liquid,move organelles and other cell contents along the fibres. This is how chromosomes are moved during mitosis.
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Flagella and Cilia
A basic cylinder that contains nine microtubules arranged in a circle, two in the central bundle. The flagella tail of the sperm moves the whole cell, whilst cilia helps move mucus in the lungs.
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Movement of Flagella and Cilia
Using ATP for energy by the microtubules.
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Differences between Flagella and Cilia
Flagella is usually longer, Cillia is smaller. Flagella normally appears in ones or twos on a cell whilst Cilia often occur in large numbers on a cell.
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Bacterial Flagella
"True motors" - Made up of a spiral of protein, attached by a hook to a protein disc at the base. Using energy from the ATP, the disc rotates, spinning the flagellum.
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Vesicles
Membrane-bound sacs found in cells. They are used to carry many substances around cells.
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Vacuoles
Large cell vacuole maintains stability. It is filled with water an solutes so that is pushes the cytoplasm against the cell wall, making the cell turgid. Turgid plant cells help support the plant.
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Plant cell walls
On the outside of the plant cell plasma membrane. Made of cellulose, Forms sieve-like network of strands to make thawed strong.
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How does the plant cell wall help support the plant?
Because it is held rigid by the pressure of the fluid inside the cell (turgor pressure).
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Structure of Nucleus
Largest organelle, surrounded by nuclear envelope. A structure made of two membranes with fluid between them. Lots of big holes (Nuclear Pores) to allow relatively large molecules to pass through. Inside the nucleus is the nucleolus a dense structure.
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Other cards in this set

Card 2

Front

What is Magnification?

Back

The degree in which the size of an image is larger than itself.

Card 3

Front

What is Resolution?

Back

Preview of the front of card 3

Card 4

Front

What is staining?

Back

Preview of the front of card 4

Card 5

Front

What is sectioning?

Back

Preview of the front of card 5
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