Organization of the Bacterial Cell pt.2 Flashcards
how does the cell wall interact with turgor pressure
the cell wall pushes back with equal and opposite force on the turgor pressure - prevents osmotic lysis
what is the importance of the cell wall
provides rigidity to lysis, provides barrier against toxic chemical and biological agents, site of action of many common antibiotics (penicillins)
why is peptidoglycan good for antibiotic development
it is only made by bacteria so the antibiotics can be made to disrupt its formation which would not disrupt the formation of the bodies cell walls
what do archaea have instead of peptidoglycan
pseudomurein
what attaches peptidoglycan to the inner leaflet in gram negative cells
lipoproteins
what distinguishes the outer membrane of gram negative cells
LPS - lipopolysaccharides
what are features of peptidoglycan
a polymer, a disaccharide connected through a beta 1,4 linkage between NAM and NAG, the peptide side chain is on NAM, the sidechain cross-links to other sidechains through the third amino acid
what is the process of peptidoglycan biosynthesis
- amino acids add sequentially to NAM 2. D-Alanine (D-Ala-D-Ala) peptide attaches (not through a ribosome) 3. NAM pentapeptide transfers to bactoprenol 4. NAG links to NAM 5. bactoprenol moves NAG-NAM from inner leaflet to outer side of membrane 6. Transglycosylase attaches new disaccharide unit to existing chain 7. A pentaglycine connects a D-Ala and Lys using PBP (peniglycin binding protein) 8. a phosphate is removed and the lipid moves back into the cytoplasm
what does penicillin, cephalosporins, vancomycin do
they inhibit cross linking in step 5 & 6 of PD biosynthesis
what does bacitracin target
prevents the bactoprenol from accepting new units of UDP-NAM - stops the recycling of bactoprenol (step 8)
what does cycloserine do
inhibits D-Ala-D-Ala peptide formation (step 2) - means that cross-linkng cannot occur
what is used to reinforce peptidoglycan in gram-positive cells
teichoic acids provide structural integrity - covalently link to membrane lipids
what do teichoic acids have in common with LPS
they are both receptors for bacteriophage
how do teichoic acids help retain the gram stain
they are negatively charges
what distinguishes the outer membrane of a gram negative cell
porins, LPS, and lipoproteins
