DD Unit 4

Question 1

What does the cell wall contain in most bacteria?

Answer 1

Peptidoglycan

Question 2

What is bacterial shape determined by?

Answer 2

Cytoskeletal elements and peptidoglycan layer forming a mesh around plasma membrane

Question 3

What is peptidoglycan?

Answer 3

• polymer with repeating N-acetylglucosamine and N-acetylmuramic acid units
• N-acetylmuramic acid units are linked to tetrapeptides (DAP, D-glutamic acid, D-alanine)
• tetrapeptides are cross-linked to D-ala (through pentaglycine in S aureus)
• *more cross linking of peptidoglycan in gram+ than in gram-
• lysozyme can hydrolyze peptidoglycan

Question 4

Gram- vs. Gram+ peptidoglycan

Answer 4

Gram-:
- thin, sparsely cross linked peptidoglycan layer with other stuff exterior to peptidoglycan

Gram+:
- thick, extensively cross linked with other stuff exterior to peptidoglycan and also teichoic acids

Question 5

What makes up the outer membrane of gram- bacteria?

Answer 5

• lipid bilayer that contains LPS, lipoproteins, porins, membrane proteins, and phospholipids

Question 6

What makes up LPS?

Answer 6

• O antigen
• Core
• Lipid A (toxic part)

Question 7

What are teichoic acids?

Answer 7

• on gram+ bacteria

- repeating polyglycerol-P or polyribitol-P backbone and covalently linked to peptidoglycan layer