ch. 3 - prokaryotic profiles: bacteria + archaea Flashcards
what differentiates prokaryotes (simplest creatures) from eukaryotes?
- the way their DNA is packaged (lack of nucleus + histones)
- the makeup of their cell wall (peptidoglycan + other chemical)
- their internal structure ( lack of membrane-bounded organelles
what do ALL bacterial cells possess?
- cell membrane
- cytoplasm
- ribosomes
- a cytoskeleton
- one (or a few) chromosomes
what do MOST bacterial cells possess?
- a cell wall
- a surface coating called a glycocalyx
what structures are only shown in SOME bacteria?
- fimbriae, pili, + flagella
- outer membrane
- plasmids
- inclusions/granules
- capsule
- endospores + intracellular membranes
what is pleomorphism?
- when the cells of one species may vary in shape + size
—– caused by variations in cell wall structure
what are the bacterial shapes?
coccus –> spherical or ball-shaped
bacillus –> rods
vibrio –> curved rods
spirillum –> helix shape with 2-3 bends (corkscrew shaped)
spirochete –> 3 or more bends (spring shaped)
branching filaments –> multiple branches off of a rod shape
what are flagella? (prokaryotic propellers)
- for bacterial locomotion
- three distinct parts
- comprised of many proteins
- 360 degree rotation
flagellar arrangement: what is monotrichous?
single flagella (1)
flagellar arrangement: what is lophotrichous?
small bunches of tufts of flagella (same site)
flagellar arrangement: what is amphitrichous?
flagella at both poles of the cell
flagellar arrangement: what is peritrichous?
flagella dispersed randomly over the surface of the cell
why do bacteria move and to where?
- avoid danger/hide
- look for nutrients
- get a host (spread)
- exchange DNA
- reach stimulus
- good environment to reproduce/ different place to live
what two ways can flagella move?
- runs: smooth lineal movement toward a stimulus
- tumbles: flagellar rotation reverses, causing the cell to stop + change its course
what is chemotaxis?
- bacteria move in response to chemical signals
- receptors bind extracellular molecules, which triggers flagellum to rotate
what are endoflagella?
- flagella is within the cell outer membrane
- spirochetes
what are fimbriae?
- used for attachment, especially to endothelial cells
what are pili?
- used for attachment + genetic exchange during conjugation
what is conjugation?
- exchanging of genetic material
do bacteria have cillia?
no
what is the glycocalyx?
- sugar covering composed of polysaccharides, proteins or both
- for attachment (sticky –> sticks to surfaces) + protection
used to avoid phagocytosis + for adhesion (biofilms)
thickness varies:
slime layer - thin
capsule - medium
biofilm - thickest
what is a capsule?
- a type of glycocalyx covering –> bound more tightly to cell + denser and thicker
- produces a sticky (mucoid) character to colonies (cells stick together
- encapsulated bacteria = have greater pathogenicity
what is a cell envelope?
- lies outside of the cytoplasm
- composed of two or three basic layers:
1) cell wall
2) cell membrane
3) outer membrane on some bacteria
what is the cell wall?
- helps determine shape of bacterium (in most)
- strong structural support = keep bacterium from bursting or collapsing bc of changes in osmotic pressure
- certain drugs target the cell wall = causing cell lysis (disintegration or rupture) of the cell
- gains rigidity from peptidoglycan
how is the peptidoglycan cell wall structured?
- long glycan (sugar) chains cross-linked by short peptide (protein) fragments
