Question

Which of the following describes a cell structure that a Gram-negative bacterium has that a Gram-positive bacteria does not have?
A. A membrane-enclosed nucleus in which DNA is stored and protected
B. A membrane-bound mitochondrion in which energy for the cell is made
C. An electrically charged sugar molecule that is attracted to sodium ions
D. An extra layer that is outside the peptidoglycan layer of the cell wall

Answer 1

A Gram- negative bacteria has a thin cell wall of Peptidoglycan which is sandwiched between the cell membrane and outer membrane. Where as, the Gram positive bacteria has a thick layer of Peptidoglycan outside their cell membrane.

Hence Gram- negative bacteria is different from a Gram- negative bacteria in because it has an extra layer that is outside the Peptidoglycan layer.

Hence the right option is D

This feature of the Gram-negative bacteria does not let crystal violet solution to soak into its Peptidoglycan layer because it is covered by the extra layer where as an Gram- positive bacteria will easy soak into crystal violet solution due to the exposed Peptidoglycan layer.

Answer 2

The answer is D. An extra layer that is outside the peptidoglycan layer of the cell wall