cell envelope Flashcards
(26 cards)
A complex series of layers surrounding the cytoplasm that:
- Controls nutrient/waste transport
- Offers mechanical protection
- Enables surface attachment
- Shields from attack
cell envelope
Surrounds cytoplasm, separates cell from the environment
Selectively permeable (protein-mediated)
cytoplasmic membrane
membrane proteins
peripheral and integral
ester bonds in
bacteria/eukarya
ether bonds in
archaea
Simple Diffusion: small, uncharged molecules
Facilitated Diffusion: via channels/carriers
passive transport
Simple Transport – 1 transmembrane protein
Group Translocation – modifies molecule during transport
ABC Transporters – uses ATP; includes binding protein, transporter, ATPase
Active transport
Maintains shape & prevents lysis
Basis for Gram classification:
cell wall
Sugars: NAG + NAM
Peptide chain varies:
Gram+: L-ala, D-glu, L-lys, D-ala
Gram-: L-ala, D-glu, DAP, D-ala
peptidoglycan (bacteria only)
Mycolic acid-rich CW
***Carbol fuchsin stains them red
acid-fast bacteria
CV-I retention → violet/blue
gram (+)
red/pink
gram (-)
Regulate ion flow across CW
teichoic acids (gram+ only)
No peptidoglycan
Often has S-layers or pseudomurein
archaeal cell wall
Glycosidic bonds between the sugar
derivatives are:______ instead of B1-4
β-1,3
covalently
bound to lipids
phospholipids+proteins+polysaccharide
: hydrophobic region, toxic component: endotoxin
lipid A
virulence
core polysaccharide
mutagenic types (serotypes); may provide
ligands for attachment & confer resistance to phagocytosis
O-specific polysaccharide
importance of LPS
facilitate surface recognition
Space between CM & OM
Contains:
Hydrolytic enzymes
Binding proteins
Chemoreceptors
CW/OM synthesis proteins
periplasm
Channels for small hydrophilic solutes
Specific vs Non-specific
porins (Outer mem only)
- found in many Bacteria and in nearly all
Archaea - outermost layer of the cell envelope
s-layer
