gram -ive outer membrane stability Flashcards
How are hydrophobic compounds excluded
saturated fatty acids of lipid A exclude them
what are the charges on phosphates of lipid A
negative charges
how are the -ive charges of lipid A neutralized
by divalent cation like magnesium 2+
What is EDTA
divalent cation chelator
what happens if you add EDTA to gram -ive bacteria
OM falls apart and contents of periplasmic space are released
What does the stability of the LPS leaflet provide as a barrier
barrier to potentially dangerous molecules like bile salts
What are bile salts
made in human liver, hydrophilic group is added to cholesterol producing an amphipathic molecule
What do bile salts function as
emulsify phospholipid membranes, can be added to media to inhibit growth of gram +ive bacteria
Name some OM proteins
receptors like FEP A and porins
Describe the structure of porins
are trimers (composed of 3 identical protein subunits). each subunit composed of 1 protein. secondary structure: a beta sheet. tertiary structure is a beta barrel that forms an open pore. R groups of aa lining the channel are hydrophilic
What are the fn of porins
lets OM fn a molecular sieve, pores are filled w/H2O that let small hydrophilic solutes pass. exclude large molecules
Can large molecules like protein pass the porins
no cannot get in or out, e.g. periplasmic proteins cannot get out
What are the 2 types of porins
non specific porins and specific
What do non specific porins permit the passage of
any hydrophilic solute that is small enough
Describe specific porins
has a constricted channel, lined w/+ively charged R groups. this promotes uptake of phosphates
