BIOLOGY - CHAPTER 2

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What is a microscope and what is it used for?
an instrument used to magnify a sample to see how it's detailed structures relate to their function
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Explain how a light microscope works, and what is the advantage of using 2 lens?
objective lens: magnifies image of specimen. eyepiece lens; further magnifies the image produced by the objective lens. ad? allows for a higher magnification, higher resolution, reduces chromatic aberration.
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State and describe the 4 types of sample preparations. Why do specimens have to be thin?
dry mount - samples are sectioned, eg dust, hair. wet mount - samples are suspended in water eg aquatic samples. squash slided - wet mount, squash eg root tip squashes. Smear slide - smear at 45 deg angle eg blood. Thin so that light can pass through
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Use of staining? Give 2 eg's of dyes
used to identify cells and distinguish between different components by increasing the contrast of the components making them more easy to identify.
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Give 2 eg's of dyes
crystal violet, methylene blue
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define differential staining
a technique that can identify between two types of organisms and differentiate between different organelles that would otherwise be hard to distinguish.
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explain how differential staining can be performed on bacteria
you would use crystal violet dye, alcohol and iodine. (+) bacteria will retain the stain and appear blue/purple under a light microscope. (-) bacteria have thinner cells walls, lose stain and have to be counterstained with safranin dye - appear red
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define magnification
how many times larger the image is than the actual size of the object being viewed
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2 factors that affect magnification?
objective lens and type of microscope - electron mic has higher mag
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define resolution
the ability to distinguish between two objects by the shortest distance and view them as separate entities
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what factor decreases resolution? increases?
diffraction; the spreading out of waves causes structures to overlap, the detail is lost so difficult to see cleary. using a beam of electrons.
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equation to calculate magnification
magnification = size of the image ( mm) / actual size of the object ( micrometers)
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conversions for magnification
1 micrometer = 1000 nm, 0.0001 cm, 0.001 mm,
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Card 2

Front

Explain how a light microscope works, and what is the advantage of using 2 lens?

Back

objective lens: magnifies image of specimen. eyepiece lens; further magnifies the image produced by the objective lens. ad? allows for a higher magnification, higher resolution, reduces chromatic aberration.

Card 3

Front

State and describe the 4 types of sample preparations. Why do specimens have to be thin?

Back

Preview of the front of card 3

Card 4

Front

Use of staining? Give 2 eg's of dyes

Back

Preview of the front of card 4

Card 5

Front

Give 2 eg's of dyes

Back

Preview of the front of card 5
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