Multiple Choice
During the Gram stain procedure, which type of cells decolorize when the alcohol is applied?
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7. Prokaryotic Cell Structures & Functions
Gram-Positive vs. Gram-Negative Cell Walls
Multiple Choice
Which of the following features distinguishes the cell wall of Gram-positive bacteria from that of Gram-negative bacteria?
A
Presence of periplasmic space between two membranes
B
A thin peptidoglycan layer and presence of an outer membrane
C
A thick peptidoglycan layer and absence of an outer membrane
D
Presence of lipopolysaccharide in the cell wall
Verified step by step guidance1
Step 1: Understand the basic structure of bacterial cell walls. Gram-positive and Gram-negative bacteria differ primarily in their cell wall composition and architecture.
Step 2: Recall that Gram-positive bacteria have a thick peptidoglycan layer, which provides rigidity and retains the crystal violet stain during Gram staining.
Step 3: Note that Gram-negative bacteria have a thin peptidoglycan layer located between two membranes: the inner cytoplasmic membrane and an outer membrane, which contains lipopolysaccharides (LPS).
Step 4: Recognize that the periplasmic space is the area between the inner and outer membranes in Gram-negative bacteria, but this space is minimal or absent in Gram-positive bacteria due to the lack of an outer membrane.
Step 5: Conclude that the distinguishing feature of Gram-positive bacteria is the presence of a thick peptidoglycan layer and the absence of an outer membrane, unlike Gram-negative bacteria which have a thin peptidoglycan layer and an outer membrane containing LPS.
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