2.4 Cell Wall

Question 1

What are the two main functions of a cell wall?

Answer 1

• Give a cell its shape

- protect from osmotic lysis/mechanical forces

Question 2

Where does the cell wall construct itself?

Answer 2

around the helical MreB proteins. Uses MreB as a scaffold.

Thnk papier-mache around a balloon

Question 3

Explain the shape/structure of the peptidoglycan layer

Answer 3

A matrix

Chain-linked fence of crosslinked strands

Question 4

What are the two types of strands in the peptidoglycan layer?

Answer 4

1. repeating glycan (sugar) units

2. crosslinked peptide chains between glycan strands

Question 5

What role does crosslinking of the peptidoglycan molecules play in cell structure?

Answer 5

Gives strength to the peptidoglycan network

Question 6

Which of the following is true of a cell that is missing its peptidoglycan layer?

It cannot properly transport solutes
It cannot maintain proper cell shape
It cannot properly maintain concentration gradients

Answer 6

It cannot maintain proper cell shape

Question 7

What are the subunits of the peptidoglycan layer?

Answer 7

N-acetylmuramic acid (NAM)
N-acetylglucosamine (NAG)
L-amino acids
D-amino acids
short peptide chain

Question 8

How does penicillin work?

Answer 8

• Inhibits Ftsl protein which in turn inhibits the bacteria from forming crosslinkes peptide chains (TRANSPEPTIDATION).
• The cell wall continues to break but does not reform itself
• cell quickly lyses (explodes)

Question 9

what is Lysozyme? what does it target?

Answer 9

an enzyme that destroys cell walls.

specifically targets β-1,4-glycosidic bonds

Question 10

What are protoplasts and what do we use them for?

Answer 10

Cells with their cell wall eaten away

Used for studying bacterial membranes and genetic manipulation

Question 11

Enzyme that cuts the pentaglycine crossbridge of peptidoglycan in Staphylococcus aureus

Answer 11

Lysostaphin

Question 12

Enzyme that degrades peptidoglycan by hydrolyzing the bond between NAG and NAM

Answer 12

Lysozyme

Question 13

How are some bacteria capable of resisting “lactam” antibiotics?

Answer 13

• they produce enzyme β-lactamase

- β-lactamase cleaves bonds within β-lactam ring and destroys the antibiotic

Question 14

If a pathogen has the ability to produce ___________, then that organism will be resistant to lactam antibiotics

Answer 14

β-lactamase

Question 15

________ acid can be added, in addition to the lactam antibiotic treatment to overcome lactam resistance. It works as a “suicide substarate” to deactivate _____________

Answer 15

Clavulanic acid deactivates β-lactamase

Question 16

Antibiotics containing beta-lactam rings interfere with synthesis of the bacterial cell wall in what way?

Interfere with membrane lipid assembly
Interfere with transpeptidation
Interfere with transglycosylation
Interfere with bactoprenol transport

Answer 16

Interfere with transpeptidation

Question 17

Enzyme that hydrolyzes penicillin, rendering it ineffective:

Lysozyme
Lysostaphin
Polymerase
β-lactamase
Transglycosylase

Answer 17

β-lactamase

Question 18

Lipid in the plasma membrane that facilitate the passage of peptidoglycan precursors?

Answer 18

bactoprenol

Question 19

What does bactoprenol do?

Answer 19

Bactoprenol transports pentapeptide precursors across the cytoplasmic membrane.