Peptidoglycans

Question 1

Gram(+) bacteria

Answer 1

Thick layer of peptidogylcan EXTERNAL to the plasma membrane

Question 2

Gram (-) bacteria

Answer 2

Thin layer of peptidoglycan located BETWEEN plasma membrane and outer membrane

So plasma membrane is still underneath it like (+)

Question 3

Basic unit of a polysaccharide chain of a peptidoglycan

Answer 3

Repeating GlcNAc

But every other GlcNAc a lactic acid forms a ether bond with the C3 OH

—> N-acetylmuramic acid (MurNAc)

So its a repeating GlcNAc, MurNAc (beta-1,4)

Question 4

Tetrapeptide side chain of the polysacc chain

Answer 4

Attaches to the lactic acid

Order:

1. L-Ala
2. D-Glut
3. L-Lys ( with a pentaglycine residue*)
4. D-A

Question 5

Cross-linking of peptidogylcan strands

Answer 5

Between the pentaglycine on the L-Lys on one strand

AND

The D-Ala of another

Enzyme: transpeptidase

Question 6

Beta-lactam antibiotics

I.e. penicillin

Answer 6

Inhibit peptidogylcan crosslinking by stopping transpeptidase

Prevent making of bacterial cell wall