Biology / Unit 9 Bio 1949 short lesson, about 20 seconds
Gram-Positive versus Gram-Negative Wall Structure
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The idea
A Gram-positive wall is a thick peptidoglycan layer alone; a Gram-negative wall is a thin peptidoglycan layer wrapped in a lipopolysaccharide-containing outer membrane.
In practice
Gram-negative bacteria's outer membrane contains lipopolysaccharides that can trigger a strong immune response, absent from Gram-positive bacteria.
Where people slip
A Gram-negative cell's thinner wall does not mean weaker — its extra outer membrane adds a separate protective layer.
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