Cell Structure and Function

1
Cell Structure and Function
2
Cell Theory

• Based upon work of Theodor Schwann, Matthais
  Schleiden and Rudolph Virchow.
• All organisms are composed of cells
• Cells are the basic units of structure and
  function in organisms
• Cells come only from preexisting cells because
  cells are self-reproducing.

3
Why are most cells microscopic?

• Cells need a large surface area to adequately
  exchange nutrients and wastes
• surface-area-to-volume ratio
• Total surface area (HxWxSxC) divided by total
  volume (HxWxLxC)
• Some organelles have microvilli, villi and rugae
  to increase surface area

4
Microscopes

• 17th century Leewenhooke
• Compound Light Microscope
• Uses light rays and glass lenses to focus

5
Transmission Electron Microscope

• Electrons pass through the specimen
• Focus by magnetic lenses
• Image projected on fluorescent screen

6
Scanning electron microscope

• Narrow beam of electrons scan surface of specimen
• Specimen is coated with metal layer
• Secondary electrons given off by metal produce an
  image on a screen

7
Magnification and Resolution

• Light microscope approx. 1000x
• TEM hundreds of thousands
• Difference is in illumination wavelength of
  electrons is shorter than wavelength of light.
• Greater resolutiongreater detail
• Resolution minimum distance between 2 objects
  at which they can still be seen as two separate
  objects.
• If humans eyes are set at 1.0, LM500, EM
  100,000 resolving power.

8
Viewing advancements

• To increase the contrast of a specimen, different
  types of light, staining and optical methods can
  be used.
• Confocal microscopy 3-D using laser beam.
• Video enhanced contrast microscopy

9
Prokaryotic Cells

• Lack nucleus and membrane bound organelles
• Can cause disease, decompose and help to make
  foods/chemicals
• Classified into 2 Domains

10
Structure

• Bacillus rod shaped
• Coccus sphere shaped
• Spirilla rigid twisted rods
• (called spirochetes if flexible)

11
Cell envelope

• Plasma membrane phospholipid bilayer embedded
  with proteins
• Regulates materials into and out of the
  cytoplasm
• Internal pouches mesosomes increase surface
  area for enzymes
• Cell wall contains peptidoglycan maintains
  shape
• Glycocalyx layer of polysaccharides outside of
  cell wall, aids in protection from immune system
  and attachment
• capsule if organized and hard to remove
• slime layer if unorganized and easy to remove

12
Cytoplasm

• Nucleoid region houses the single circular
  strand of DNA
• Plasmid extrachromosomal piece of circular DNA
  used as vector in GE
• Ribosomes
• Inclusion body stored nutrients

13
Cyanobacteria

• Photosynthetic bacteria
• Contain thylakoids in cytoplasm that contain
  chlorophyll that absorb solar energy to produce
  carbs.
• Release oxygen

14
Appendages made of protein

• Flagella locomotion, made of filament, hook and
  basal body
• Fimbriae small, bristlelike fibers on surface
  of cell, attachment
• Sex Pili rigid tubular structures, exchanging
  DNA - conjugation

15
Domain Archaea

• No peptidoglycan in cell wall
• More diverse in shape
• May be more closely related to eukaryotes because
  of biochemical make-up.
• Live in extreme habitats, like those of long ago