2.5 Variation in Cell Envelope

Question 1

Most bacteria are Gram________

Answer 1

megative

Question 2

The Gram stain is based on ….

Answer 2

the width of the cell wall

whether or not the cell has an outer membrane

Question 3

In the results of a Gram stain, the gram ________ bacteria are purple and the gram _______ are red

Answer 3

positive -> purple

negative -> red`

Question 4

What are the steps (briefly) of the gram staining process?

Answer 4

Crystal violet stains cells
Iodine traps the colour
Alcohol decolourization shrinks large pores in Gram-positive cells and locks crystal violet stain in
Alcohol strips away some outer membrane lipids in Gram-negative cells
Safranin stains Gram-negative cells pink

Question 5

A major difference between Gram-positive and Gram-negative cell envelopes is that

peptidoglycan is only found in Gram-positive cell walls.
lipopolysaccharides are only found in Gram-negative envelopes.
periplasm is only found in Gram-positive envelopes.
teichoic acids are only found in Gram-negative walls.
transport proteins are only found in Gram-negative cytoplasmic membranes.

Answer 5

lipopolysaccharides are only found in Gram-negative envelopes.

Question 6

Space between the inner membrane and outer membrane in bacteria is called the ___________.

Answer 6

periplasm

Question 7

Bacterial cells with a thin layer of peptidoglycan in the cell wall surrounded by an outer membrane; lose crystal violet stain in the Gram-stain procedure and appear pink.

Answer 7

Gram-negative

Question 8

Teichoic acid in the Gram-positive cell wall that is attached to the plasma membrane is called a .

nucleic acid
hydroxy unit
lipoteichoic acid
peptidoglycan

Answer 8

lipoteichoic acid

Question 9

Outer membrane in Gram-negative bacteria is a _____________ layer

Answer 9

lipopolysaccharide (LPS)

Question 10

Channel in the outer membrane of Gram-negative bacteria that allows movement of nutrients

Answer 10

porin