Common Shapes of Prokaryotes
spherical shape
coccus
Cell Envelope (includes cell wall)
the cell envelope is made of 3 layers:
outer membrane ; cell wall made of peptidoglycan or murein ; cell or inner membrane
what is selective permeability?
transports and controls movement of molecules in and out of cytoplasm; small uncharged molecules via passive diffusion
what powers flagella movement?
swimming locomotion; has a basal body with a ring of motor proteins around rotor; rotary motor powered by the proton motive force
other shape
Rods or Bacilli
what is under the cell envelope?
Cell Membrane
- function-rich cell membrane
- internal most layer of cell envelope
- phospholipid bilayer, rich in membrane proteins
what does the cell wall do?
provides structural strength, resistance to osmotic pressure
forms proton (h+) gradient (& other ion gradients)
Proton Motive Force
how does a flagella swim?
counterclockwise: flagellar bundle forms; straight line = run
clockwise: no bundle; random tumble
alternating runs and random tumbles
other common shapes
(3 options)
Spirilla, Vibrios, Filamentous
contains few internal structures/organelles; simple cytoskeleton
cytoplasm
what is peptidoglycan?
component of cell wall/envelope; long linear chains of amino acid sugars
it detects...
environmental signals
what is an example of swimming with purpose?
chemotaxis: moving towards a chemical attractant (tumbling decreases)
type of cocci colony
Chain colony
common external feature
Flagellum
what is the difference between a gram-positive and gram-negative cell?
gram-positive: peptidoglycan wall thick (10-20 layers); retains purple stain
gram-negative: peptidoglycan wall thin; additional outer membrane; does not retain stain, stays pink
what is active transport?
what do pili and fimbriae do?
adhesion (in genetic exchange and pathogenesis) and locomotion (on surfaces)
other type of cocci colony
Cluster
genome & dna rich area; contains single circular chromosome
Nucleoid
- small compact genome
what is in the outer membrane?
outer leaflet: mostly lipopolysaccharide
inner leaflet: contains major lipoproteins = hydrophobic tails + proteins
porins: hollow round shape; beta barrel proteins; allows for passage of small molecules; aqueous water filled channels
what is the cell membrane made of?
phospholipid bilyaer
what are flagella made of?
usually made of proteins