4.1 Cellular level of organization

Cell theory :

• all organisms are cimposed of cells

• all cells come from preexisting cellls

• cells are the smallest structural and functional unit of organisms

Cell size

• cells range in size from one millimeter down to one micrometer

• cells need a large surface area of plasna membrane to adequatley exchange materials

the surface-tovolume-rattio requires that cells be small

• large cells - surface area relative to volume decreases

• small cells - larger surface area to volume ratio is advantages for exchanfe of materials

Prokaryotic cells

• lack a membrane bound nucleus

• structurally smaller and simpler than eukaryoticv cells (which have a nucleus)

• Peokaryotic cells are placed in two taxonomic domains

  • bacteria

  • and archea

    • live in extreme habirars

  • domains are structurally similar but biochemically different

The structure of prokaryotes

• extremely small : 1-1.5 um wide and 2-6 um long

• occur in three basic shaoes

  • spherrical coccus

  • rod shaped bacculus

  • spirap spirrilum (if rigid) or spirochete (if fkexible)

• Cell envelope includes plasma membrane - lipid bilayer with with imbdedd and peripheral protein

  • form internal puches (mesesomes)

• cell wall- maintains the shape of the cell and is strengthened by peptidoglycan

• glococalyx- a layer of polysaccaharides on the ouside of the