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Microbial Structure: Cell Envelope (Common Bacterial Shapes (coccus:…
Microbial Structure: Cell Envelope
Functions of The Bacterial Envelope
cell characteristics
partially responsible for structure and shape
toxic and immunological properties of the cell associated with envelope
may be responsible for some signs/symptoms of disease
protection
from osmotic inbalances
from elimination by phagocytosis and infection by viruses
from chemotherapeutic agents: creating a thicker cell wall
metabolic functions
attachment and colonization of environmental surfaces
site of envelope-associated enzymatic activities
origin of many signal transduction pathways
Common Bacterial Shapes
coccus: spherical
bacillus: rod shaped
vibrio: curved rod
spiral: spiral shape
spirochete: cork screw, tight spiral
Common Bacterial Arrangements
diplo: 2
tetrad: 4
sarcinae: cube
strepto: chain
staphylo: clusters
Important Membrane Functions
Barrier
phospholipid bilayer, peripheral/integral proteins, carbohydrate modifications (glycolipid)
keeps things in or out despite chemical gradients and osmotic pressure
modern medicine takes advantage --> losing integrity of membrane is lethal to cell
hopanoids can be put into the membrane to increase rigidity
Transport
passive transport: high-->low
simple diffusion
facilitated diffusion
channel protein
carrier protein: changes shape to transport
active transport: low-->high
primary: uses ATP
uniport: move 1 thing
cotransport: move 2 things, both low to high
secondary
symport: spontaneous and nonspontaneous movement are coupled, use energy from spontaneous to power nonspontaneous
antiport: same as symport but spontaneous and nonspontaneous are in opposite directions
common bacterial transporters
simple transport: driven by the energy of in the proton motive force (couple something unfavorable with proton gradient)
group translocation: chemical modification of transported substance driven by phosphoenolpyruvate (add phosphate to glucose to move it)
ABC transporter: periplasmic binding proteins are involved and energy comes from ATP (ATP binding cassette: protein binds to substrate and transports it to complex, scavenge to find substrate)
Secretion: type II bind to substrate, unfold protein and cause to leave cell; RND: proton motive force pumps things out of cell (antibiotics)
Response
membrane receptors will initiate a cellular response to stimuli
when receptor encounters a stimulis the signal is sent out which causes a response
chemotaxis: movement toward chemical stimuli; phototaxis: movement toward light
Division
prokaryotic division: septum forms and separates daughter cells, 2 sides of septum meet in middle
FtsZ: assembles at septum, contacts where septum forms
Reactions
ETC and photosynthesis occur in membrane
endosymbiotic theory: prokaryotic cells combined to make eukaryotic cells; mitochondria and chloroplasts have DNA
mesosomes: folds in membrane to increase surface area, increase reactions, different shapes and sizes depending on function