Multiple Choice
Which of the following bacteria are not reliably identified using a Gram stain?
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7. Prokaryotic Cell Structures & Functions
Gram-Positive vs. Gram-Negative Cell Walls
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The Gram stain works because of differences in the ________ of bacteria.
A
cell wall structure
B
plasma membrane composition
C
ribosomal RNA sequences
D
flagellar arrangement
Verified step by step guidance1
Understand that the Gram stain is a differential staining technique used to classify bacteria into two groups: Gram-positive and Gram-negative.
Recall that the key difference between Gram-positive and Gram-negative bacteria lies in their cell wall structure, specifically the thickness and composition of the peptidoglycan layer.
Recognize that Gram-positive bacteria have a thick peptidoglycan layer that retains the crystal violet stain, appearing purple under a microscope.
Know that Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane, which does not retain the crystal violet stain but takes up the counterstain (safranin), appearing pink or red.
Conclude that the Gram stain works because of differences in the cell wall structure of bacteria, not plasma membrane composition, ribosomal RNA sequences, or flagellar arrangement.
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