basic components of living systems

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  • Created on: 18-04-17 18:57
Outline the importance of microscopes in the study of living organisms
The cell is a unit of life, many organisms are unicellular, and most of these are too small to see without microscopes. The organelles in these cells are even smaller and we need to see them to determine their function. Before the 19th century micros
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State the resolution and magnification that can be achieved by a light microscope, a transmission electron microscope and a scanning electron microscope.
The light microscope uses light rays which have a large wavelength so they produce images of a poor resolution (0.2µm). Light microscopes produce coloured images that can only view larger organelles (nucleus, vacuole, cell wall, cell membrane) and ce
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Explain the difference between magnification and resolution.
Magnification is the number of times larger the image is relative to the original object. Resolution is the ability to distinguish between two objects that are close together – in other words when the different objects in the image are visibly distin
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Explain the need for staining samples for use in light microscopy and electron microscopy
Stains are needed to make these structures / organelles visible by increasing the contrast, as different structures / organelles absorb stain differently allowing identification. The specimens must be thin so light can pass through it, furthermore th
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Calculate the linear magnification of an image.
Magnification size = Image size / Actual size
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Why are gram negative infections more difficult to treat then gram positive ones?
Gram negatives have thinner cell walls, which are not susceptible to penicillin as the membrane around the gram negative prevents the entry of penicillin. In gram positive bacteria penicillin inhibits the formation of cell walls.
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Give the benefits of using more than one lens
The objective lens magnifies the specimen and the eyepiece lens magnifies this image so there is a higher magnification than would be produced with just one image.
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Explain why you would see more detail with an electron microscope than light microscope.
Electron microscopes use electrons instead of light and electrons have a shorter wavelength than light which produces images with a higher resolution.
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Define the term artefact with reference to microscopy.
An artefact is a visible image or distorted cell structure present in an electron micrograph due to the sample preparation process.
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Explain why artefacts are more likely to be produced when preparing samples for electron microscopy than light microscopy.
There is more sample preparation in the electron microscopy leads to more damage in the specimen and this damage leads to artefacts.
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Outline the advantages of SEM and TEM microscopy.
The transmission electron microscope has visible organelles and a greater magnification. However, they produce 2D images of very thin specimens. Furthermore, as very thin specimens are needed more preparation is involved so there are more artefacts.
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Explain the meaning of the term florescence. State why lasers are used to provide illumination.
Florescence answers an emission of light that has been absorbed. Lasers are used to increase the intensity of light.
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Explain the purpose of the pinhole aperture in confocal microscopy.
To scatter the light and light from outside the focal plane is eliminated. This reduces blurring and increases the resolution.
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One limitation of confocal microscopy is that it can’t be used for deep tissue imaging. Explain why.
The light penetration of the sample is limited.
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Card 2

Front

The light microscope uses light rays which have a large wavelength so they produce images of a poor resolution (0.2µm). Light microscopes produce coloured images that can only view larger organelles (nucleus, vacuole, cell wall, cell membrane) and ce

Back

State the resolution and magnification that can be achieved by a light microscope, a transmission electron microscope and a scanning electron microscope.

Card 3

Front

Magnification is the number of times larger the image is relative to the original object. Resolution is the ability to distinguish between two objects that are close together – in other words when the different objects in the image are visibly distin

Back

Preview of the back of card 3

Card 4

Front

Stains are needed to make these structures / organelles visible by increasing the contrast, as different structures / organelles absorb stain differently allowing identification. The specimens must be thin so light can pass through it, furthermore th

Back

Preview of the back of card 4

Card 5

Front

Magnification size = Image size / Actual size

Back

Preview of the back of card 5
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