Cell Wall gram +ive Flashcards
What is fn of peptidoglycan
gives cell its shape, protects cell from lyses in a hypotonic sln
What do gram -ive bacteria cell walls have
thin peptidoglycan layer attached to OM by lipoproteins
What does pepti and glycan mean
chain of aa and sugar
what is the structure of the glycan
2 alternating sugar derivatives. 1st is N-acetyl-glucose-amine. second is N-acetyl-muranic acid (NAG with a lactic acid attached). glycan chain coils up
What are peptide bridges
peptides attaches to NAMs, some peptides covalently linked to other nearby peptides. linking glycan chain to form a sheet, and sheets together to form giant strong 3-D macromolecule
describe gram +ive cell wall
teichoic acids attached to PM and to thick peptidoglyan layer, peptidoglycan is 30 layers thick, forms a mesh that is permeable to small non polar molecules and ions
What is the linkage of peptides in gram +ive cell walls
peptides attaches to the NAMs as penta peptides. composed of N-1l-ala-2d-glu-3l-lys-4d-ala-5d-ala-c. linkage of interbridge is to penta peptide
What is the interbridge
additional peptide common in gram +ive
What is the interbridge of Staphylococcus aureus composed of
5 glycine in a row, attached to a L-lysine of a pent peptide
Why can the R group of L-lysine be covalently linked to C terminus of interbridge
b/c it is a diamino acid
What happens to the N terminus of the interbridge
is covalently links to C terminus of another penta peptide. terminal D-ala is lost, not a tetra peptide. 70% of cross links formed
Describe the structure of teichoic acid
polyanionic polymer of either glycerol phosphate or ribitol phosphate that extend through peptidolgycan
What are attached to the sugar alcohols (ribitol and glycerol)
other sugars like glucose or a.a. like D-ala
When is it only called teichoic acid
if attached to the NAM of the peptidoglycan
When is it called lipoteichoic acid
if attached to the phospholipid of PM
