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CHAPTER 7: A TOUR OF THE CELL
RESOLUTION
Human Eye
0.1mm, 100µm, 100,000.0nm.
Light Microscope 0.0002mm 0.2µm, 200.0nm 2000.0Å
S.E.M.
0.002µm 2.0nm 20.0Å
T.E.M.
0.0001µm 0.1nm. 1.0Å
wavelength of light
wavelength of electrons
0.4--0.7µm. 400—750nm.
0.0054nm--0.0000054nm
Theoretically 130,000 times better resolution
Now only 2,000 times better resolution
Transmission
Electron
Microscope TEM
TEM
Scanning Electron
Microscope SEM
TEM
SEM
Light Microscope
SPECIMEN PREPARATION
1. Staining
a. light--use pigmented molecules which are absorbed
differentially by the specimen
b. T.E.M.-- use heavy metals; which are also absorbed
differentially
c. S.E.M.--not necessary
2. Fixation--use a chemical which will tie the tissue together and
prevent distortion of structures during the other steps of
preparation
a. glutaraldehyde--forms cross linkages among protein molecules
b. osmium tetroxide --cross links lipid molecules together
3. Dehydration—to prevent destruction when placed in vacuum
alcohol washes then freeze-drying to remove all
water; not necessary w/ light microscope
4. Slicing-necessary with light and T.E.M.--embedded in paraffin
(light) or plastic resin (T.E.M.) then sliced very thin with an
ultra-microtome OR
5. Coating-S.E.M. cover the surface with a 2-3 atom thick layer of
gold or silver
homogenization
differential centrifugation
supernatant
pellet
Would the presence or absence of a cell wall distinguish
a prokaryotic cell from a eukaryotic cell?
Binary fission
Golgi apparatus
Bound ribosomes make proteins that will
be secreted from the cell
Lysosome destroying
worn-out organelles
Some storage diseases such as Tay-Sachs are caused
lysosomes that are defective.
Plant cells have mitochondria too.
Beating of cilia
and flagella
Movement of
organelles,
cytoplasmic
streaming
Anchors for the spindle fibers during mitosis.
9+2
9+0
Basal body
anchor for cilia
and flagella
9 pairs around 2
9 triplets around none
microfilaments attach to microtubules and contract and
pull on them
Plant cells can grow longitudinally by adding more
cellulose to their primary cell walls but cannot grow after
forming their secondary cell wall.
Extracellular
matrix
fibronectin
Glycoproteins
95% carbohydrate
Full
Empty
Contractile vacuoles
nuclei
actin
actin
Actin and keratin