Textbook Question
Which cellular structure is important in classifying a bacterial species as Gram positive or Gram negative?
a. Flagella
b. Cell wall
c. Cilia
d. Glycocalyx
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7. Prokaryotic Cell Structures & Functions
Gram-Positive vs. Gram-Negative Cell Walls
Multiple Choice
Why are penicillins often more effective against gram-positive bacteria than gram-negative bacteria?
A
Penicillins are unable to bind to the cell wall of gram-positive bacteria.
B
Gram-negative bacteria have a thick outer membrane that prevents penicillins from reaching the peptidoglycan layer.
C
Gram-positive bacteria have a thick peptidoglycan layer that is easily accessible to penicillins.
D
Gram-negative bacteria lack peptidoglycan in their cell walls.
Verified step by step guidance1
Understand the structure of bacterial cell walls: Gram-positive bacteria have a thick peptidoglycan layer, while gram-negative bacteria have a thinner peptidoglycan layer but possess an additional outer membrane.
Recognize the mechanism of action of penicillins: Penicillins inhibit the synthesis of peptidoglycan, which is essential for bacterial cell wall integrity.
Analyze why penicillins are more effective against gram-positive bacteria: The thick peptidoglycan layer in gram-positive bacteria is exposed and accessible, allowing penicillins to bind and inhibit cell wall synthesis effectively.
Consider the barrier in gram-negative bacteria: The outer membrane in gram-negative bacteria acts as a protective barrier that limits the penetration of penicillins to the peptidoglycan layer, reducing their effectiveness.
Evaluate the incorrect statements: Penicillins do bind to gram-positive bacteria cell walls, and gram-negative bacteria do have peptidoglycan, just less accessible due to the outer membrane.
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