10+ Year Member
Jan 25, 2007
Resident [Any Field]
In the EK Biology Content book, I think there is an error in Lecture 3 Microbiology, Section 3.7 Bacterial Envelope on p. 64-67.

The book says gram-positive bacterium have a periplasmic space.
"Gram-positive bacteria have a cell wall that is approximately four times thicker than the plasma membrane. The space between the plasma membrane and the cell wall is called the periplasmic space."

"In gram-negative bacteria, the periplasmic space is the space between the two membranes."

I always learned gram positive bacteria have a plasma membrane and cell wall, while gram negative bacteria have a plasma membrane, cell wall, periplasmic space, and outer membrane. Thus I thought the periplasmic space + outer membrane are unique to gram-negative bacteria.

What should we go by for the MCAT?

Online sources also indicated that "periplasmic space" is absent in gram positive bacteria so is EK wrong?
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