Bacterial Cell Wall

Question 1

What is Gram - made up of

Answer 1

inner cell membrane
Peptidoglycan
Periplasm
Outer cell membrane

Question 2

What provides strength to peptidoglycan and why is it useful

Answer 2

Cross linking provided by transferase enzymes

Used for turgidity

Question 3

What is the peptidoglycan structure?

Answer 3

Glycan chains made of NAG and NAM which are linked to peptide chains (L-ala, D-glutamic acid, DAP, D-ala) although the peptide chains may vary between species

E.g pentoglycine chains in strahyloccocus aureus.

The peptidoglycan subunit is the monomer for its synthesis

Question 4

How is the peptidoglycan synthesised

Answer 4

1. 1st the monomer is made and assembled on lipid carrier molecule like Und-PP and occur in cytoplasm of inner membrane. (monomer is NAM plus 4 aminoacids). with use of enzymes MurA-F - LIPID 1
2. Lipid 1 binds to Mray integral membrane protein where NAG - UDP binds to Lipid 1 making the Lipid 2 subunit. which is catalysed by MurG
3. FtsW Enzyme causing it to flip membrane.
4. This is then incorporated into peptidoglycan by (Glycosyl transferase enzyme) GTase

UDP released and recycled

Question 5

Gram + is made up of

Answer 5

• inner cell membrane
• peptidoglycan cell wall (thicker then negative)
• cytoplasm

Question 6

How does cross linking occur in Gran negative bacteria

Answer 6

From DAP to D-ala of adjacent chain peptide bond is formed on D-ala carboxyl group.

Question 7

How does cross linking occur in Gram positive bacteria

Answer 7

Occurs via interbridge. in Staphylococcus

aureus the interbridge is made up of 5 glycine residues.

Question 8

Antibiotics that target cell wall synthesis

Answer 8

Vancomyosin
Penicillins

(Beta - lactams) 50% of antibiotics

Question 9

Penicillins are good against which type of bacteria and why

Answer 9

Gram positive as no membrane present to can block Gtase activity and stop crosslinkages occuring. then lysis occurs

Question 10

what causes the negative charge in bacteria

Answer 10

Teichoicacid

polymers of glycerol and ribitol and contain phosphates which cause its charge.