Small, smaller, smallest

1
Small, smaller, smallest

• Science uses the metric system
• Each unit differs by 1000x (103)
• Example length. (same prefixes for moles, etc.)
• Millimeter 1 x 10-3 meter
• Micrometer 1 x 10-6 meter
• Nanometer 1 x 10-9 meter
• Angstrom 1 x 10-10 meter
• Picometer 1 x 10-12 meter

2
Not all sizes are measured in lengths

• Molecules are too small to talk about length
• Units are molecular weight grams/mol
• i.e. how much do 6.023 x 1023 molecules weigh?
• Molecular weight units often daltons
• Large molecules kilodaltons (Kd) 1000 x dalton
• Some large molecules Particles measured in
  Svedbergs
• Svedberg based on migration rate in a centrifuge
• Both mass and shape affect size of units
• RNA molecules, ribosomes, viruses

3
Something cant be smaller than the parts it is
made of!
Sand is used to make bricks, and bricks are
assembled to make a house. A house cant be
smaller than a brick a brick cant be smaller
than grains of sand. Likewise, small molecules
are combined to make polymers and polymers are
used to make cells.
cic.nist.gov/lipman/sciviz/scan/jun24_ptC1a.jpg
www.littleitalymd.com/images/BrickLayer.gif
www.kevscartoons.com/images/illustration/chil...
4
In the world of small, whats big?

• Cells of eukaryotic organisms are big
• Nerve cells can be quite long
• White blood cells are about 10 µm in diameter
• An amoeba may be around 20 µm
• Prokaryotes and cell organelles are smaller
• E. coli is about 1 µm long
• A mitochondrion is about the same size
• Particles are smaller
• Viruses range from 20 to 200 nm (0.02 0.2 µm)
• Ribosomes, found inside cells, are about 20 nm

5
In the world of small, whats smaller?

• Ribosomes, viruses, cell walls are made of
  polymers
• Ribosomes and viruses are combinations of
  proteins and nucleic acids
• Cell walls are made of large molecules like
  peptidoglycan and lipopolysaccharide
• Polymers are larger than the monomers they are
  made of
• Proteins range from 10,000 to 500,000 MW
• Most enzymes are proteins (if it ends in -ase)
• Bacterial DNA is over 1 mm long! (but very
  skinny)
• Polysaccharides can be gt 100,000 MW (grams/mol)

6
In the world of small, whats smallest?

• These are all small molecules ranging from 18
  g/mol to 1,000 g/mol
• Water, oxygen gas, nitrogen gas
• Sugars (glucose, sucrose, etc.)
• Amino acids
• Nucleotides
• Fatty acids, cholesterol, (even phospholipids
  arent big)
• Organic acids found in metabolism
• Vitamins
• Antibiotics and most other drugs

7
The study of chemistry and biochemistry is
necessary to understand Microbiology
Habitat
Diet
8
Why Chemistry?
Conflict between microbe and host.
Vibrio cholera toxin inserting into intestinal
cells. Review Chemistry
9
Microscopy

• 3 Basic terms
• Magnification to make things appear larger
• Resolution (resolving power) the ability to
  distinguish two points as being separate
• Contrast differences in light intensity between
  an object and the background.
• Empty magnification
• An increase in magnification without an
  accompanied increase in resolution (points
  larger, but conitnue to overlap)

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Resolution
On the left low resolution, multiple objects
appear continuous. On the right improved
resolution individual points are now
visible. Note that in both, contrast is
good. The white bar is 200 nm, so magnification
is also quite good.
The limit of resolution of the human eye is about
0.1 mm. Since microbes are typically 0.001
0.005 mm, magnification is required to seem them
individually.
http//www.microscopy-analysis.com/download/380/He
ll.jpg
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Optical laws

• Light travels in waves
• ? wavelength of light
• visible light 400 700 nm
• Numerical aperture
• a characteristic of the quality of the lens
• a measure of the light gathering capacity of the
  lens
• Resolution is affected by both
• Resolution (r) 0.61 ? /NA
• where r is the smallest distance at which two
  points can be distinguished as being separate.

http//www.windows.ucar.edu/physical_science/magne
tism/images/visible_spectrum_waves_big.jpg
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Types of Light microscopy

• Brightfield
• specimen appears grey/stained background is
  bright
• Darkfield
• specimen appears bright background is dark
• Phase contrast
• light is slowed down after hitting specimen,
  becomes out of phase w/ background light
  (destructive interference)
• specimen appears very dark (or bright) light
  background
• Differential interference Contrast (DIC)
• Nomarski optics, prism changes speeds of light
• shadowed effect, lights, darks, 3D appearance