Bacterial Cell Walls Flashcards
What are the properties of a Gram + Cell Wall?
Thick Peptidoglycan layer. No outer LPS membrane. Teichoic Acids embedded in wall
What are the properties of a Gram - Cell Wall?
Smaller Cell Wall. Smaller Peptidoglycan. Periplasmic space between Cytoplasmic Membrane and Outer Lipopolysaccharide Membrane.
What is the structure of Peptidoglycan?
Backbone: N-Acetylmuramic Acid and N-Acetylglucosamine bound by a B-1,4 Linkage.
Peptide Units attached to backbone
Interbridge connecting Backbone repeats
What is a characteristic property of the B-1,4 Linkage?
Broken by Lysozyme
What interbridge is in Gram - Bacteria?
Diaminopielic Acid
What interbridge is in Gram + Bacteria?
Lysine
What makes the Cell Wall Rigid?
The repeating structure of Peptidoglycan
What is the importance of the Interbridge?
Connects each layer of the wall together
Linkages from one cell to the other
Provides Rigidity
What is the First Step in Peptidoglycan Synthesis?
New Peptidoglycan GlcNAc-MurNAc disaccharide unit made inside cell and transported across cytoplasmic membrane by ABC transport system.
What is the Second Step in Peptidoglycan Synthesis?
Outside of the cell, Autolysins cleave the B-1,4 Linkage in the existing Peptidoglycan chain
What is the Third Step in Peptidoglycan Synthesis?
Carrier lipid puts new disaccharide in place
What is the Fourth Step in Peptidoglycan Synthesis?
Transpeptidtation Reaction creates new bonds between the layers
What are the Two Key Steps in the Transpeptidation Reaction?
- Removes One D-Alanine from existing Peptidoglycan chain.
2. Links adjacent GlcNAc-MurNAc strands with interbridge
What step of Peptidoglycan Synthesis does Penicillin act on?
The Transpeptidation Reaction
How does Penicillin kill bacteria?
It does not kill bacteria directly, but it stops them from growing. It makes bacteria unable to from new interbridges. With weakened Peptidoglycan layer, cells are more susceptible to die on their own.
