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CHAPTER 1 - CELL STRUCTURE
MICROSCOPY
-the technical field of using microscopes to view sample and objects that are not
within the resolution range of the normal age
1mm - 0.001µm
1mm - 1000µm (micrometres)
1µm - 1000nm (nanometer)
MAGNIFICATION
-the number of times larger an image is than the objects (specimen)
-same unit is used for the size of image and object
Magnification = size of image / size of object
RESOLUTION
-the ability to distinguish between two points on an image (amount of detail)
-the larger the wavelength, the lower the resolution
-400-600nm for visible light
LIGHT MICROSCOPE
-where in a specimen is dyed and illuminated with light which is focused using a
glass lens
-has a resolution of approximately 200 nm (< than electron microscope)
ADVANTAGES DISADVANTAGES
1)Cheap to purchase and operate 1)Magnifies objects up to 2000x
2)Small and portable 2)Dept of field is restricted
3)Unaffected by magnetic field
4)Preparation of material is quick and
simple, requiring little expertise
5)Natural colour of material can be
observed
, ELECTRON MICROSCOPE
-use a beam of electrons to create image of the specimen
-shorter wavelength than light = higher resolution
-only display dead specimens as they need to be placed in a vacuum
-has a higher resolution of 0.5nm
ADVANTAGES DISADVANTAGES
1)magnifies object over 500000x 1)expensive to purchase and operate
2)possible to investigate a greater depth 2)very large and must be operated in
of field special rooms
3)affected by magnetic fields
4)preparation of materials require
expertise
5)all images are in black and white
PROKARYOTES VS EUKARYOTES
PROKARYOTES
1)average diameter of cell is 0.5 -5 µm (smaller than eukaryotic cells)
2)does not have a nucleus or nuclear membrane
3)lack many organelles such as mitochondria
4)DNA :- circular, single loop, lies free in the cytoplasm, naked
5)have 70s ribosomes and no ER present
6)cell wall present containing peptidoglycan
7)some have flagellum
8)mostly made up of a single cell
EUKARYOTES
1)diameter of 40µm
2)contain nucleus bounded by nuclear membrane
3)have many types of organelles such as endoplasmic reticulum, mitochondria, etc
4)have 80s ribosomes
5)DNA :- not circular (linear), contained in a nucleus, associated with protein forming
structures called chromosomes
6)cell wall is present sometimes for example plants have cellulose cell wall and fungi
has cell wall made of chitin
7)may be multicellular or single-celled organisms
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