Uses light which shines from under the specimen from a bulb through the stage and into the condenser which produces the image.
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Maximum magnification
x 1500
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Maximum resolution
0.2 um
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Magnification definition
How much bigger an image is compared to the specimen
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Resolution definition
The amount of detail in the image. Are you able to distinguish between organelles.
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What are the two types of electron microscope?
TEM and SEM
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What does TEM stand for?
Transmission Electron Microscope
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What does SEM stand for?
Scanning Electron Microscope
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How does a TEM work?
Electromagnets focus an electron beam which is then transmitted through the specimim
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How does a SEM work?
Scans a beam of electrons across the specimen.
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Maximum magnification of a TEM?
Greater than x 1,000,000
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Maximum resolution of a TEM?
0.0001 um
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Maximum magnification of a SEM?
Less than x 1,000,000
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Maximum resolution of a SEM?
0.005 um
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Advantages of a light microscope
Inexpensive, portable, natural coloured and undistorted images.
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Disadvantages of a light microscope
Low magnification and low resolving power
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Advantage of TEM
High resolution image
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Disadvantage of TEM
Can only be used on very thin specimen
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Advantage of SEM
Produces a 3-D image.
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Disadvantage of SEM
Lower resolution and magnification compared to TEM
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Advantages of electron microscopes
High resolution and high magnification images
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Disadvantages of electron microscopes
Expensive, not portable, images are black and white
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Why do we use staining in microscopy?
Biological molecules are colourless when thinly sliced. Increase contrast. Make the image clearer. Identify and distinguish organelles. Identify compounds as cells bind to different molecules.
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What stain is used in light microscopy?
Dye
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What stain is used in electron microscopy?
Objects are dipped in a solution of heavy metals. Metal ions scatter electrons creating contrast.
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Magnification equation
Magnification = Image size/ Actual size
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What are the three key organelles involved in protein synthesis?
Ribosomes, endoplasmic reticulum and the Golgi apparatus
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Ribosomes
Site of protein synthesis. Either found free in the cytoplasm or attached to the rough endoplasmic reticulum
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What is the ER?
Endoplasmic reticulum - Network of membranes enclosing flattened sacs called cristernae.
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What are the two types of ER?
Smooth and rough endoplasmic reticulum
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Smooth endoplasmic reticulum
Responsible for lipid and carbohydrate, synthesis and storage.
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Rough endoplasmic reticulum
Ribosomes are bound to the surface, responsible for processing and packaging proteins
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Secretory cells
Release hormones or enzymes. They have more rough ER than those cells which do not release proteins.
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Golgi apparatus
It is a compact structure formed of cristernae. It is responsible for modify and packaging proteins into vesicles. Either secretory vesicles which leave the cell or lysosomes which remain in the cell. They don't contain ribosomes.
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What do mitochondria and chloroplasts both contain?
Ribosomes
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What are ribosomes made from?
Made from RNA and are not membrane bound organelles/
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