Ultrastructure of Cells

The resolution of electron microscopes
1. better than light microscopes
2. resolution - separate parts distinguishable
3. light microscopes - max x400
4. shorter wavelength = higher resolution
Prokaryotic cell structure
1. simple; no compartments
2. no nucleus
3. first organisms
4. mostly small
5. found everywhere
6. cell wall outside cell membrane
  1. thicker and stronger
  2. protection
  3. maintains shape
  4. prevents from bursting
  5. wall contains peptidoglycan
  6. called extracellular
7. filled with cytoplasm
8. complex in terms of biochemicals
9. no cytoplasmic organelles apart from ribosomes
  1. 70S ribosomes
  2. smaller than in eukaryotic cells
10. DNA in cytoplasm, usually one circular molecule
11. lighter part of cell called nucleoid
12. naked DNA
Cell division in prokaryotes
1. divide by binary fission
2. asexual reproduction
3. single circular chromosome replicated
  1. moves to opposite ends of the cell
    1. division of cytoplasm
      1. each daughter cell contains one chromosome copy
        genetically identical
Eukaryotic cell structure
1. compartmentalized cell structure
2. partitions are single or double membranes
3. nucleus contains cells chromosomes
4. organelles with distinctive structure and function
5. advantages of compartmentalization
  1. enzymes and substrates more concentrated
  2. damaging substances kept separate
  3. conditions such as pH can be kept different
  4. organelles with their contents can be moved around the cell

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