2.4 Flashcards
(28 cards)
Outer membrane
only gram negative
the second membrane outside cell wall
what does outer membrane consist of
LPS, lipopolysaccharide, and phospholopid
outer membrane symmetry
asymmetrical
the outer leaflet is mostly LPS with little phospholipid
the inner leaflet is phospholipids
what are the three parts of LPS
lipid A- within memb
core polysaccharide- connecting
o-specific polysaccharide- outer
lipid A structure
-hydrophobic tails anchor lipid A in OM, this is the base of LPS
phosphates confer a negative charge
what is lipid A also known as?
endotoxin, sensed by immune system and leads to potent immune response causing septic shock
o specific polysaccharides also called
o antigen
o specific polysaccharides structure
-diverse sugar subunits connected and branched
-repeating combination of sugar
o antigen diversity and its importance
can be used to identify specific bacterium as they are highly variable from lineage to lineage
what anchors the cell wall to the outer membrane
brauns lipoprotein
where are brauns lipoproteins abundant?
gram negative cells
how does brauns lipoprotein work>
lipid anchors in OM and the other end is covalently attached to peptidoglycan
what are porins
-protein channels in OM that are channels for entrance/ exit of small molecules
-can be specific or non specific
what are the functions of the outer membrane
provide mechanical strength to cell using ionic bonds between LPS molecules via divalent metal ions
- important barrier
-antibiotic sensitivity, closes porins for certain molecules
-protects cell wall(ie. from lysozym that chews it)
-enables periplasmic space
Periplasm
gram negative bacteria
space between inner/ outer membrane
periplasm functions
-buffer b/w environment and cell
-good for detoxification
-protein folding
-high affinity binding protein for
nutrients
-break down macromolecules for uptake
what bond is important for protein folding
disulfide bond formation
S layers
-protein coat
rigid/ permeable monolayer or glycoprotein
-self organized repeating structure
-outermost layer of cell
functions of S layer
protective layer, protects from bacteriophages or bacterio pathogens
-provides periplasmic space or keep external proteins from accessing OM or CW
what domains produce s layers
more common in archaea
some bacteria
what are capsules or slime layers
coats of polysaccharides around cell surface
difference between capsule and slime layer
capsules: organized into matrix and attach to cell
slime layers loosely attaches and less organized
functions of capsules and slime layers
adjearing to surface, protection from host immune cells (bacterial pathogens), protection from dehydration
pili
protein filaments that extend from cell surface
