What is the independent variable?
The variable that you change
What is the dependent variable?
The variable that you measure
What is the control variable?
The variable that you keep the same
What is the magnification of the eyepiece lens on a light microscope?
10x
What is the equation for working out the magnification of a light microscope?
The magnification of the eyepiece lens multiplied by the magnification of the objective lens. For example if the magnification of the objective lens was 40x then the magnification of the light microscope would be 40x10= 400x
What is the eyepiece graticule?
The eyepiece graticule is a measurement device on light microscopes that has 100 divisions, it has an arbitrary scale and can be used to calculate the length of one epu (eye piece unit) on different magnifications
Hw do you find the value of one epu at a specific magnification (40x)?
- You find the number of epu that corresponds to the number of large divisions on the stage micrometer
- For example if 80 small divisions on the eyepiece graticule corresponds to 18 large divisions on the stage micrometer then the length of the stage micrometer is 180um because each large division on the stage micrometer is worth 10um so 18x10+ 180um
- You then do 180um which is the length of the stage micrometer and divide it by the number of epu (80) needed to make up the length (180um) of the stage micrometer
- So 180/80= 2.25um which is the value of one epu on the 4x objective lens so a total magnification of 40x
What are the uses of staining?
- To highlight a particular organelle eg. the nucleus. Acetic orcein can be used to do this as it stains chromosomes a purple-red colour
- To distinguish between different cell types eg. red blood cells and white blood cells
- To distinguish different tissue types eg. smooth muscle tissue, epithelial etc.
What is the stain for red blood cells?
Eosin
What is the stain for white blood cells?
Haematoxylin
What is the formula for magnification?
Image / Actual
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Membranes52
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Cell Structure67
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Key Concepts11
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Enzymes55
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Biological Molecules105
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Practical Skills16
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Communicable Diseases81
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Cell Division49
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Transport in Plants24
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Photosynthesis23
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Respiration28
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Excretion88
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Nucleic Acids41
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Cellular control33
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Communication and Homeostasis39
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Exchange Surfaces and Breathing47
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Transport in Animals82
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Transport in Plants66
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Patterns of Inheritance12
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Hormonal Communication49
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Neuronal Communication3
