CHAPTER 3.3

Question 1

Bacteria Cell Envelope

Answer 1

the structure surrounding the bacterial cell membrane which can consist of: the cell wall, outer membrane, and sometimes the cytoplasmic membrane (in gram negative!)

Question 2

Gram-Negative Bacteria

Answer 2

• E. Coli
• cell wall is significantly smaller
• periplasmic space between the cell wall and cell membrane
• has another layer on the outside of cell wall
• has LPS (lipopolysaccharides) protruding from the cell

Question 3

Gram-Positive Bacteria

Answer 3

• S. aureus
• cell wall is VERY thick compared to gram negative
• periplasm between the space of cell wall and cell membrane
• on the surface of the cell wall, lipoteichoic acid protrudes from the cell

Question 4

Periplasm is _______
Periplasmic space is _______

Answer 4

Periplasm is the space between the cell wall and membrane for GP bacteria
Periplasmic space is between the space of cw and membrane for GN bacteria

Question 5

What is the cell wall for

Answer 5

structural support and protection from osmolarity changes

Question 6

Peptidoglycan

Answer 6

• makes up the cell wall
• made up of long chains of sugars (polymers of sugars) connected by short peptides

Question 7

what do gram-positive cell walls have?

Answer 7

teichoic acid- polymers that maintain cell wall structure

lipoteichoic acid- anchor the wall to the membrane

Question 8

what protrudes gram-negative outer membranes have LPS

Answer 8

present in the outer membrane of gram-negative bacteria

Question 9

what are the four chemicals, in order, involved in gram stain

Answer 9

-Crystal violet (Primary stain): good for GN and GP
- Iodine (mordant): reinforces the CV dye inside GP
- Alcohol (or acetone): washes out GN, shows GP
- Saffrinin: good for gram negative bacteria, appearing pink. gram positive stays purple since they retain crystal violet.